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Multiple factors explain the covering behavior in the green sea urchin, Strongylocentrotus droebachiensis
Abstract
Although numerous species of sea urchins often cover themselves with small rocks, shells and algal fragments, the function of this covering behaviour is poorly understood. Diving observations showed that the degree to which the sea urchin Strongylocentrotus droebachiensis covers itself in the field decreases with size. We performed laboratory experiments to examine how the sea urchin's covering behaviour is affected by the presence of predators, sea urchin size, wave surge, contact with moving algae blades and sunlight. The presence of two common sea urchin predators did not influence the degree to which sea urchins covered themselves. Covering responses of sea urchins that were exposed to a strong wave surge and sweeping algal blades were significantly greater than those of individuals that were maintained under still water conditions. The degree to which sea urchins covered themselves in the laboratory also tended to decrease with increasing size. Juveniles showed stronger covering responses than adults, possibly because they are more vulnerable to dislodgement and predation. We found that UV light stimulated a covering response, whereas UV-filtered sunlight and darkness did not, although the response to UV light was much weaker than that to waves and algal movement. Our observations suggest that the covering behaviour of S. droebachiensis has evolved as an adaptation to protect it from mechanical injuries associated with abrasion and dislodgement, and to a lesser extent as a defence against UV radiation. The covering behaviour may reduce the sea urchin's ability to move and this would limit its ability to forage and to flee from predators. In this case, the covering behaviour may have evolved as a trade-off between locomotion and limiting environmental stresses.
... This behaviour has multiple evolutionary origins in various ecological and morphological contexts and includes cnidarians, molluscs, polychaetes, arthropods, and echinoderms (Berke et al. 2006). In some species, this behaviour changes ontogenetically, with greater coverage during the juvenile phase, or persists throughout their life (Dumont et al. 2007;Hultgren and Stachowicz 2009). ...
... Numerous studies have described covering behaviour in sea urchin species, with Mortensen (1943) being one of the pioneers in describing this phenomenon in coastal species. This behaviour, which involves the total or partial covering of the sea urchin by placing various items on its aboral surface, has been observed in species from tropical, subtropical, temperate and polar waters (Dayton et al. 1970;Dumont et al. 2007) and in species belonging to the families Echinolampadidae, Urechinidae, Echinometridae, Glyptocidaridae, Strongylocentrotidae, Parechinidae, Toxopneustidae, Palaeotropidae, Echinidae and Temnopleuridae (Ziegenhorn 2017). The significance of various environmental factors likely fluctuates depending on the microhabitat and the sea urchin species under examination (Dumont et al. 2007). ...
... This behaviour, which involves the total or partial covering of the sea urchin by placing various items on its aboral surface, has been observed in species from tropical, subtropical, temperate and polar waters (Dayton et al. 1970;Dumont et al. 2007) and in species belonging to the families Echinolampadidae, Urechinidae, Echinometridae, Glyptocidaridae, Strongylocentrotidae, Parechinidae, Toxopneustidae, Palaeotropidae, Echinidae and Temnopleuridae (Ziegenhorn 2017). The significance of various environmental factors likely fluctuates depending on the microhabitat and the sea urchin species under examination (Dumont et al. 2007). While it is more commonly recorded in shallow waters, sea urchins with covering behaviour have been also found in deep waters (~3000 m) (Levin et al. 2001;Pawson and Pawson 2013). ...
The sea urchin Pseudechinus magellancus exhibits a covering behaviour through which it captures different items from the environment and arranges them on its aboral surface with the assistance of podia. The items mainly used include detached algae and inorganic items available in the substrate. Spatial (between sites) and vertical (along a coastal depth gradient from intertidal tidepools to upper circalittoral zones) variability was found in the composition of covering items, indicating that coverage is strongly influenced by the availability of the utilised items. Inorganic biogenic items (eg shell remnants) were prevalent in the lower intertidal, while detached algae predominate in subtidal environments. A positive selection of larger items from those available in the environment was found at least in the intertidal tidepools. The species exhibited an equal degree of coverage between juveniles and adults, and also a higher proportion of individuals with high coverage in the intertidal zone compared to the subtidal zone. The degree of coverage between sites with dissimilar sediment input was similar. The covering behaviour in P. magellanicus may not be a response to a single factor but rather an advantageous trait with multiple functions that could have been selected simultaneously.
... O motivo para tal comportamento ainda não é totalmente entendido e ainda há algumas discussões. Algumas das hipóteses são: (1) camuflagem para evitar predadores (AMSLER et al., 1999;SCHEIBLING;HAMM, 1991), (2) proteção contra os raios ultravioleta (R-UV) (ADAMS, 2001;KEHAS et al., 2005;MILLOTT, 1956), (3) proteção contra injúrias mecânicas associadas à presença de ondas (DUMONT et al.,2007;LEVIN et al., 2001) O objetivo desse trabalho foi, portanto, (1) examinar a prevalência do comportamento de cobertura na população de ouriços-do-mar da espécie em questão a partir das amostragens em campo; (2) verificar a influência do tamanho dos ouriços-do-mar (diâmetro do corpo: considerando ou não os espinhos), da profundidade e da distância para a terra firme na quantidade dos materiais encontrados sobre os ouriços-do-mar e (3) descrever os tipos de materiais encontrados sobre os ouriços-do-mar. ...
... 1; Fig. 2). Isso pode indicar que os indivíduos localizados em áreas mais rasas estão mais expostos aos raios ultravioleta e/ou estariam mais visíveis aos predadores visualmente orientados (MILLOTT, 1956;DUMONT et al., 2007). Cobrir-se com materiais disponíveis no fundo dos oceanos poderia, portanto, protegê-los da radiação solar e, ao mesmo tempo, camuflá-los, escondendo-se dos predadores (DUMONT et al., 2007;SIGG et al., 2007). ...
... Isso pode indicar que os indivíduos localizados em áreas mais rasas estão mais expostos aos raios ultravioleta e/ou estariam mais visíveis aos predadores visualmente orientados (MILLOTT, 1956;DUMONT et al., 2007). Cobrir-se com materiais disponíveis no fundo dos oceanos poderia, portanto, protegê-los da radiação solar e, ao mesmo tempo, camuflá-los, escondendo-se dos predadores (DUMONT et al., 2007;SIGG et al., 2007). ...
O ouriço-do-mar Lytechinus variegatus apresenta o comportamento de cobertura que consiste em colocar vários materiais submersos sobre seu corpo. As hipóteses para explicar tal comportamento são bastante discutidas e ainda não há um consenso. Estão associadas com (1) camuflagem para evitar predadores, (2) proteção contra os raios ultravioleta (R-UV), (3) proteção contra injúrias mecânicas associadas à presença de ondas e movimento abrasivo das algas submersas e (4) com o tamanho do animal. O objetivo desse trabalho foi: (i) examinar a prevalência desse comportamento na população de ouriços-do-mar; (ii) descrever os tipos de materiais encontrados sobre os ouriços-do-mar e (iii) verificar a influência do tamanho dos ouriços-do-mar, da profundidade e da distância para a terra firme, na quantidade dos materiais encontrados sobre os ouriços-do-mar. Em média, cada ouriço-do-mar apresentou 5,5 ± 4,5 materiais sobre ele. Oito distintos materiais foram encontrados. O mais comum foi um tipo de folha de angiosperma terrestre, seguida por concha de bivalves. A análise de correlação entre as variáveis mostrou que somente a profundidade correlacionou-se negativamente e significativamente com a quantidade de materiais sobre os ouriços-do-mar, sugerindo que os indivíduos localizados em áreas mais rasas e, provavelmente, com maior incidência de R-UV e/ou mais visíveis aos predadores visualmente orientados, apresentaram mais materiais em cima do corpo.
... Aggregation may function to hold larger food items to facilitate feeding for groups of individuals, though Nishizaki and Ackerman (2004) found that small urchins did not appear to bene t from aggregations with larger urchins. Urchins also tend to hold inanimate objects like shell fragments on their aboral surfaces, which may have a defensive function (Dumont et al. 2007). Cover, competition, and the general environmental context, likely impacts foraging behavior. ...
... Urchins tended to aggregate and to hold both organic and physical objects close to them. These behaviors have been reported for S. droebachiensis and other sea urchins previously (Tegner and Dayton 1977;Garnick 1978;Bernstein et al. 1981Bernstein et al. , 1983Dumont et al. 2007). In addition, they actively moved in the direction of a food source (Propp 1977;Garnick 1978;Lauzon-Guay and Scheibling 2007). ...
... The process of preparing the cages for a trial might be considered a threatening event, even if there was no direct contact as shadows from the experimenters would be detected by the urchins through their light sensitive podia (Yoshida et al. 1984;Lesser et al. 2011). It is also possible that the covering behavior may have been stimulated solely by the room light (Dumont et al. 2007), since long-term white light exposure affects righting and foraging behavior in the congener S. intermedius (Yang et al. 2021), a species also sensitive to light intensity (Sun et al. 2019), and many urchins are nocturnal. ...
Foraging behavior is known to have drastic impacts across the animal kingdom, from the behavior of vertebrates as well as invertebrates. Green sea urchins ( Strongylocentrotus droebachiensis ) are well known omnivorous echinoderms that display a wide diversity of behavioral responses to chemical and tactile stimuli. Green sea urchins likely consider the stimuli of conspecific presence especially in foraging environments where competition can be high. The foraging behavior, specifically ability to reach a food item, of urchins was examined in four distinct trials with urchins under competitive and non-competitive environments with conspecifics after determining the preferred animal protein. Two trials examined the effect of cover type, and the other two considered urchins with no available cover in different water flow regimes. Overall, urchins competing with conspecifics were faster to reach food than those that were alone. However, when cover was available, non-competitive urchins most often did not reach the food item in the time allotted. Urchins likely weigh the risk and benefits of moving towards high value food with the competitive environment and cover type. These results indicate the importance of considering the conspecific environment in urchin behavioral studies and can have implications for aquaculture.
... Many animals have evolved a range of strategies to protect themselves from stresses and covering behavior, where animals actively cover themselves with materials from the surrounding environment, is observed in many insect larvae, spiders, crabs and sea urchins (Dumont et al., 2007). Lytechinus variegatus is a very common sea urchin on shallow sandy bottoms of tropical and subtropical western Atlantic, exhibits rapid growth, early reproductive maturity, and short longevity, characteristics of a ruderal species (Hill and Lawrence, 2003;Watts et al., 2007). ...
... L. variegatus covering behavior have been suggested to occur due to several reasons, such as protection against predators (Moore et al., 1963;Watts et al., 2007), as ballast to avoid displacement by wave action or strong currents (Sharp and Gray, 1962), as a lever in righting behavior (Lawrence, 1976) and as protection against ultraviolet light (Sharp and Gray, 1962;Sigg et al., 2007). This behavior may have evolved as a trade-off between locomotion and limiting environmental stresses (Dumont et al., 2007) but covering in L. variegatus have been https://doi.org/10.1016/j.marpolbul.2020.111188 Received 9 March 2020; Received in revised form 15 April 2020; Accepted 15 April 2020 mostly associated with protection against ultraviolet light (Millott, 1955;Sigg et al., 2007;Watts et al., 2007). ...
... The present study is the first survey to show that marine debris is potentially impacting an important animal covering behavior. Such behavior may have evolved as a trade-off between locomotion and limiting environmental stresses for urchins (Dumont et al., 2007). Previous studies have compared covering materials by species of urchins and showed that Lytechinus variegatus covered a large proportion of its body with material that was most available in the environment (Amato et al., 2008). ...
Notwithstanding impacts of marine debris on fauna by ingestion and suffocation, little is known about debris-related behavior. Lytechinus variegatus is a common sea urchin known for its covering behavior. We hypothesized that L. variegatus would select more marine debris (i.e. litter) than natural material as cover and we also expected that the selected natural and artificial material would be different in weight, sizes and transparency. We haphazardly collected marine debris and natural material on 20 individuals of L. variegatus and on the bottom, around each individual. All sampled material was weighed, measured and classified regarding opacity, nature (natural or artificial). Our results showed that i) sea urchins picked more litter than natural objects, ii) proportional weight of litter carried by urchins was significantly larger than expected by chance, iii) when considering all objects (on urchins and on the bottom) litter was heavier, wider and less opaque than natural material and iv) litter carried by the urchins were wider and less opaque than natural material. We suggest that litter can influence urchin's protection against sunlight, camouflage and ballast and that sea urchins with covering behavior might be used as indicators of marine debris in coastal and deep waters.
... Some species of echinoids, however, are able to tolerate high light intensities and temperatures (Glynn 1968), while others are also able to acclimatize to it (Millott 1956). Dumont et al. (2007) suggest multiple factors for this behavior in Strongylocentrotus droebachiensis, ranging from resistance to strong waves, predation, mechanical injury, and to a lesser extent, defense against UV radiation. ...
... The bulk of covering behavior studies on urchins were performed on temperate or polar species (Amsler et al. 1999on Sterechinus neumayeri, Adams 2001and Dumont et al. 2007 on Strongylocentrotus droebachiensis). Studies of tropical sea urchins are mostly on feeding biology (Pennings & Svedberg 1993), population biology (Bak et al. 1984, Iken et al. 2010, and ecology (Ogden & Carpenter 1987, Bak 1990) with limited or no consideration on the negative phototactic covering behavior. ...
... The covering behavior of Strongylocentrotus purpuratus was not triggered by light, but can be best described as a tactile response (Douglas 1976). A multi-factorial explanation was proposed by Dumont et al. (2007), citing that the covering behavior of Strongylocentrotus droebachiensisis more on the response of dislodgement from the substrate due to wave action, and that the behavior is more pronounced especially among juveniles. They also noted the behavior as a response to predation and protection from UV radiation, nevertheless their experiments yielded unequivocal conclusions which favored the latter. ...
The tropical urchin Salmacis sphaeroides is commonly observed covering itself with pieces of debris that it picks up from the substrate using its tube feet. This behavior is understood to be a response to bright sunlight. We exposed adult Salmacis sphaeroides to four different light treatments, i.e., dark, photosynthetically active radiation (PAR), UV-C and PAR+UV-C, and quantified the rate of covering response using aluminium foil discs as covering material. Another objective was to demonstrate the harmful effect of UV-C on the covering response of sea urchins. Test urchins covered themselves considerably when exposed to PAR, while urchins under UVC+PAR covered themselves slightly more than under UV-C alone. Urchins with the least covering response were from the dark treatment. The experiments demonstrate that S. sphaeroides is negatively phototactic and that exposure to UV-C may hinder this response, presumably due to physiological stress.
... Certain wavelengths of ultraviolet radiation (UVR) can induce cellular damage in aquatic organisms (Lesser and Barry, 2003). Adult S. droebachiensis exhibit a shade seeking or covering response when exposed to UVR, which may confer some protection from damage (Adams, 2001;Dumont et al., 2007). Dumont et al. (2007) found that sea urchins collected from shallow water (2 m) in the Gulf of St. Lawrence exhibit a stronger response to UVR than those from deeper areas (15 m), well below the 10% irradiance depth for UVR penetration (2 to 3 m; Kuhn et al., 1999). ...
... Adult S. droebachiensis exhibit a shade seeking or covering response when exposed to UVR, which may confer some protection from damage (Adams, 2001;Dumont et al., 2007). Dumont et al. (2007) found that sea urchins collected from shallow water (2 m) in the Gulf of St. Lawrence exhibit a stronger response to UVR than those from deeper areas (15 m), well below the 10% irradiance depth for UVR penetration (2 to 3 m; Kuhn et al., 1999). Adams andShick (1996, 2001) found UVR-absorptive compounds (mycosporine-like amino acids) in eggs and embryos of S. droebachiensis, although exposure to UVR did not stimulate production of these substances in the gonads of adults . ...
... Many sea urchins display covering behavior by holding materials from the surrounding environment, such as calcareous shell fragments or pieces of macroalgae, against the aboral surface with their tube feet. Juvenile S. droebachiensis in barrens in the Gulf of St. Lawrence exhibit a higher frequency of covering behaviour than adults (Dumont et al., 2007). In laboratory experiments, the presence of a predator (crab or sea star) had no effect on the frequency of the covering response, suggesting that covering behavior has evolved primarily to protect sea urchins against environmental stressors, such as wave action and UVR, and may reduce their ability to forage or flee from predators (Berke et al., 2006;Dumont et al., 2007). ...
... Several species of sea urchins cover their exposed body surfaces, in a special form of crypsis, with debris collected from their environment [1][2][3][4][5]. The debris can be biotic or abiotic in nature, and include scleractinian coral rubble, mollusc shells, sea grass, terrestrial leaves, and human rubbish. ...
... The sea urchins actively manipulate these debris fragments with their tube feet and combine these with their spines to transport them onto their upward facing body surface. Suggested reasons for this behavior are UV protection (demonstrated for Tripneustes gratilla [5,6]), olfactory camouflage (suggested for covering species living in light-deficient deep-sea environments [7,8], and use as a ballast for weighing down of the animal by increasing the relative density of the sea urchin in the face of currents or surge (shown for Strongylocentrotus droebachiensis [2] and for Paracentrotus lividus [9]) as well as a direct anti-predatory function [1,10]. It has been shown that sea urchins increase their coverage if faced with stressors such as UV radiation and wave action [2,6]. ...
... Suggested reasons for this behavior are UV protection (demonstrated for Tripneustes gratilla [5,6]), olfactory camouflage (suggested for covering species living in light-deficient deep-sea environments [7,8], and use as a ballast for weighing down of the animal by increasing the relative density of the sea urchin in the face of currents or surge (shown for Strongylocentrotus droebachiensis [2] and for Paracentrotus lividus [9]) as well as a direct anti-predatory function [1,10]. It has been shown that sea urchins increase their coverage if faced with stressors such as UV radiation and wave action [2,6]. Urchins were even capable of distinguishing between two types of artificial covering material, and preferred the type that was more conductive to UV protection [5]. ...
We compared the covering behavior of four sea urchin species, Tripneustes gratilla, Pseudoboletia maculata, Toxopneustes pileolus, and Salmacis sphaeroides found in the waters of Malapascua Island, Cebu Province and Bolinao, Panagsinan Province, Philippines. Specifically, we measured the amount and type of covering material on each sea urchin, and in several cases, the recovery of debris material after stripping the animal of its cover. We found that Tripneustes gratilla and Salmacis sphaeroides have a higher affinity for plant material, especially seagrass, compared to Pseudoboletia maculata and Toxopneustes pileolus, which prefer to cover themselves with coral rubble and other calcified material. Only in Toxopneustes pileolus did we find a significant corresponding depth-dependent decrease in total cover area, confirming previous work that covering behavior serves as a protection mechanism against UV radiation. We found no dependence of particle size on either species or size of sea urchin, but we observed that larger sea urchins generally carried more and heavier debris. We observed a transport mechanism of debris onto the echinoid body surface utilizing a combination of tube feet and spines. We compare our results to previous studies, comment on the phylogeny of sea urchin covering behavior, and discuss the interpretation of this behavior as animal tool use.
... transport them onto their upward facing body surface. Suggested reasons for this behavior are UV protection (demonstrated for Tripneustes gratilla, (Belleza, Samuel and Jr, 2012;Ziegenhorn, 2016)), olfactory camouflage (suggested for covering species living in dark deep-sea environments, (David, Magniez and Villier, 1999;Brothers et al., 2016)) and use as a ballast for weighing down of the animal in the face of currents or surge (shown for Strongylocentrotus droebachiensis, (Dumont et al., 2007)) as well as direct anti-predatory function (Zhao, Ji, et al., 2014) (Agatsuma, 2001). ...
... Furthermore, since the covering material is often edible for the urchins (sea grass, coralline algae), covering has been suggested as a food storage behavior (Dix, 1970;Douglas, 1976). It has been shown for UV radiation and wave action (Dumont et al., 2007;Belleza, Samuel and Jr, 2012), that urchins increase their coverage if faced with these stressors. Different species of urchins have been shown to be selective for the covering material used (Amato et al., 2008). ...
... We only found an increased debris coverage with depth in Toxopneutes pileolus, which confirms the purpose of the covering behavior as UV protection and weighting down to counter water movement seen in previous studies (Adams, 2001;Dumont et al., 2007;Belleza, Samuel and Jr, 2012;Ziegenhorn, 2016). The limited depth range at which we sampled the other species might have contributed to the lack of depth dependence of coverage which we found. ...
We compared the covering behavior of four sea urchin species, Tripneustes gratilla, Pseudoboletia maculata, Toxopneutes pileolus, and Salmacis sphaeroides found in the waters of Malapascua Island, Cebu Province and Bolinao, Panagsinan Province, Philippines. Specifically, we measured the amount and type of covering material on each urchin, and, in several cases, the recovery of debris cover after stripping the animal of its cover.
We found that Tripneustes gratilla and Salmacis sphaeroides have a higher preference for plant material, especially sea-grass, compared to Pseudoboletia maculata and Toxopneutes pileolus , which prefer to cover themselves with coral rubble and other calcified material. Only for Toxopneutes pileolus did we find a decrease in cover with depth, confirming previous work that the covering behavior serves UV protection. We found no dependence of particle size on either species or urchin size, but we observed that larger urchins carried more and heavier debris. We observed a transport mechanism of debris onto the echinoid body surface utilizing a combination of tube feet and spines. The transport speed of individual debris items varied between species.
We compare our results to previous studies of urchin covering behavior, comment on the phylogeny of urchin covering behavior and discuss the interpretation of this behavior as animal tool use.
... Covering behavior refers to sea urchins using their tube feet and spines to move objects, such as shells, stones and algae fragments, onto their dorsal surface in both shallow water (Verling et al. 2002) and the deep sea (Pawson & Pawson 2013). A number of hypotheses have been proposed to explain the potential functions of covering behavior in sea urchins, including reflex action (Lawrence 1976), ancillary feeding (Douglas 1976), protection against predation (Agatsuma 2001), wave surge (Millott 1975), floating debris (Richner & Milinski 2000) and over-exposure to light (Verling et al. 2002;Kehas et al. 2005;Dumont et al. 2007). Sheltering behavior, by contrast, is a behavioral habit of sea urchins to inhabit shelters, which vary from small crevices to large reefs. ...
... The behavioral mechanisms leading to covering behavior in sea urchins remain largely unknown, although a number of studies have provided convincing evidence for both reflex action (Lawrence 1976) and biologic functions (Richner & Milinski 2000;Agatsuma 2001;Dumont et al. 2007). In the present study, we found that test size, body weight, tissue growth, tissue indexes and gonad development of sea urchins kept in conditions suitable for covering behavior (availability of shells) long term showed no significant differences from those of urchins cultured in the control conditions with only kelp provided. ...
... This clearly indicates that shells as a special condition suitable for covering behavior have no more benefits to the fitness-related traits of G. crenularis than kelp alone, which is used both for food and covering. It has been well documented that covering behavior of sea urchins can be significantly increased by various environmental pressures, including solar radiation (Verling et al. 2002;Kehas et al. 2005;Dumont et al. 2007), floating debris (Richner & Milinski 2000), strong waves (Dumont et al. 2007) and predators (Agatsuma 2001). This raises an interesting question as to whether conditions suitable for covering behavior (e.g. ...
We know of no comparative assessment on the benefits and costs of long-term covering and sheltering behaviors in sea urchins. The present study investigated the long-term effects of conditions suitable for sheltering and covering behaviors on fitness-related traits of sea urchins Glyptocidaris crenularis. In general, conditions suitable for covering and sheltering behaviors significantly affected the fitness-related traits of G. crenularis in a long-term laboratory study of 31 months. Glyptocidaris crenularis kept in conditions suitable for sheltering behavior (bricks with openings) showed significantly lower test size, body weight, organ (test, lantern, gonad and gut) weights, gonad index and slower gonad development than those kept in conditions suitable for covering behavior (presence of shells) and the control conditions (without conditions for covering and sheltering). However, the index of maximum pressure resistance of the test was significantly higher in G. crenularis kept in the sheltering conditions than those in the covering and control conditions. The present study provides new insight into the mechanisms of covering and sheltering behaviors and has implications for the conservation and aquaculture of sea urchins.
... In sea urchins (class Echinoidea), cryptic behavior involves using tube feet in conjunction with spines to hoist and secure materials to the aboral surface [3], or, in the case of floating materials, seizing objects directly with tube feet [4]. Though this behavior is exhibited by several different urchin species, it remains a poorly understood phenomenon [5], and reasons for covering are thought to differ between species. Some species, like Stronglyocentrotus drobachiensis, cover to a higher degree when exposed to wave surges [5], while in other species such as Evichinus chloroticus covering is mainly a form of food capture [6]. ...
... Though this behavior is exhibited by several different urchin species, it remains a poorly understood phenomenon [5], and reasons for covering are thought to differ between species. Some species, like Stronglyocentrotus drobachiensis, cover to a higher degree when exposed to wave surges [5], while in other species such as Evichinus chloroticus covering is mainly a form of food capture [6]. ...
... In the case of the urchin Tripneustes gratilla, commonly known as the "collector urchin", many possible hypotheses for covering behavior have been explored, including protection from predators, protection from light exposure, and protection from strong currents [7]. In several studies, a correlation between light intensity and urchin cover was noted [5,7], and it has been postulated that Tripneustes covering behavior is a form of protection from the sun [8]. This conclusion is bolstered by the urchin's ability to sense and respond to light via photo-sensitive tube feet [9]. ...
Many sea urchin genera exhibit cryptic covering behaviors. One such behavior has been documented in the sea urchin Tripneustes gratilla, and previous studies have theorized that this behavior serves as protection from UV radiation. However, other hypotheses have been presented such as protection from predators or added weight to help T. gratilla resist strong currents. A field study was conducted in October-November 2015 in Moorea, French Polynesia to assess urchin covering behavior in natural habitats. The study found that urchins partially underneath rocks covered more, and with more algae, than urchins totally underneath rocks. To test if this behavior was driven by light intensity, a series of 30-minute experimental trials were run on 10 individuals in bright and dim conditions. Individuals were given red and clear plastic, and percent cover of each was recorded. These tests were repeated once fifty percent of spines had been removed from the urchin, in order to determine whether spine loss affects T. gratilla covering behavior. The study found that urchins had a distinct preference for cover that best protects them from UV radiation. Spine loss did not significantly affect urchin ability to cover, and urchins with removed spines still preferred opaque cover. Additionally, covering behavior was mapped onto a phylogeny of echinoderms to determine how it might have evolved. Understanding urchin covering behavior more fully is a step towards an understanding of the evolution of cryptic behavior across species.
... Size distribution (relative weight) of the particles larger than 4 mm found in the sediment (dark bars) and on the sea urchin (light bars) at three locations. Analysis of covariance of the transformed mass (cubic root) of the particles with their surface area (square root) as a covariate across locations (factor 1) and sources of the particle (urchins vs sediment: factor 2). was expressed as a semi-quantitative index (Dumont et al., 2007) most of the urchins were assigned a covering index of 2-3 corresponding to over 50% cover. On the tropical species Toxopneustes roseus (Agassiz, 1863) off the coast of Baja California and at the same depth as this study (9.6-11.6 m) only 38% of the aboral surface of the urchins was covered by debris (James, 2000) and on a photograph of Toxopneustes pileolus in Taiwan, the cover seems to reach nearly 90% (Chen & Soong, 2010) with coral fragments. ...
... Our observations support the other hypotheses that explain covering behavior. The large, mostly mineral and opaque debris, found on the urchins provide effective protection from light or UV light ( Verling et al., 2002;Dumont et al., 2007) and also from suspended particles (Richner & Milinski, 2000). Similarly, the covering of the urchin by particles collected from the sediment, may provide effective camouflage from predators (Dumont et al., 2007). ...
... The large, mostly mineral and opaque debris, found on the urchins provide effective protection from light or UV light ( Verling et al., 2002;Dumont et al., 2007) and also from suspended particles (Richner & Milinski, 2000). Similarly, the covering of the urchin by particles collected from the sediment, may provide effective camouflage from predators (Dumont et al., 2007). Our results also support the food storage hypothesis (Dix, 1970) because most of the large particles collected on the urchins were covered with turf and encrusting coralline algae that T. pileolus consumes (James, 2000). ...
Many sea urchin species collect debris on their aboral surface, a behavior collectively described as "covering behavior". In the Sultanate of Oman, the flower sea urchin, Toxopneustes pileolus, systematically shows this behavior, accumulating pieces of dead coral, pebbles, and fragments of various mollusks shells on its test. We compared the amount, size distribution, and relative volumetric mass of the covering material in three T pileolus populations using both underwater image analysis and physical analysis of collected debris. The underwater photographic method to estimate test cover was a good predictor of the actual amount of debris on the test (R2 = 0.85). Thxopneustes pileolus, preferred covering itself with the largest pieces of debris available in the surface sediment, but did not select pieces according to relative density. There were no significant differences in percentage cover neither among urchins of different diameters nor among urchins collected in different populations. We discuss these results in relation to various advanced hypothesis on the function of the covering behavior.
... This result demonstrates that the pigmentation of a sea urchin affects its covering behavior; compared with sea urchins with high melanin, those with low melanin were more sensitive to light, particularly to light of shorter wavelengths. According to Dumont et al. (2007), green sea urchins (Strongylocentrotus droebachiensis) engage in covering behavior mainly to protect themselves from physical hazards such as radiation and waves (Dumont et al., 2007). Therefore, this study inferred that the sea urchin was the most threatened and stimulated by the blue LED light, followed by the full-spectrum light and then the red LED light, which was the closest to a dark environment. ...
... This result demonstrates that the pigmentation of a sea urchin affects its covering behavior; compared with sea urchins with high melanin, those with low melanin were more sensitive to light, particularly to light of shorter wavelengths. According to Dumont et al. (2007), green sea urchins (Strongylocentrotus droebachiensis) engage in covering behavior mainly to protect themselves from physical hazards such as radiation and waves (Dumont et al., 2007). Therefore, this study inferred that the sea urchin was the most threatened and stimulated by the blue LED light, followed by the full-spectrum light and then the red LED light, which was the closest to a dark environment. ...
This study aims to evaluate the effect of light-emitting diodes (LEDs) of different wavelengths on the embryonic development, covering behavior, righting behavior, and phototaxis of collector urchins (Tripneustes gratilla). The collector urchins were divided into three groups according to the type of LED illumination they received: full-spectrum (400–750 nm wavelength), red light (630 nm), or blue light (450 nm). The results of the embryonic development experiment indicated that the blue LED group had the highest proportion of embryos reaching the prism stage at the 24th hour and the highest proportion of embryos entering the 4-arm pluteus stage, but it also had the highest death rate at the 48th hour. The full-spectrum and red LED groups exhibited similar speeds of embryonic development. In the experiment on covering behavior performed on adult urchins, our findings indicated that the blue LED group gripped the most acrylic sheets for cover, exhibiting the most covering behavior, followed by the full-spectrum group and then the red LED group. Moreover, behavior varied with coloration, as collector urchins with a lower level of melanin exhibited more covering behavior than those with a higher melanin level. In addition, the righting behavior experiments demonstrated that the blue LED group spent the longest time righting themselves. It is possible that the relatively strong stimulation from the blue LED illumination led to a higher level of stress in the collector urchins and hence slowed their righting. The phototaxis experiment revealed the most significant negative phototactic response in collector urchins when they were under the blue LED light, followed by the full-spectrum light; the red LED light did not induce any positive or negative phototactic response in the collector urchins. This experimental result verified collector urchins’ high sensitivity to and dislike of the blue LED light. The study results confirmed that the blue LED light environment accelerated the embryonic development of collector urchins; however, the relatively strong stimulation from that light also caused them to engage in covering behavior or move away from the light. These results indicate that short-wavelength irradiation significantly affects the embryonic development and behavior pattern of this species.
... We focused on how two behavioral traits might determine prey survival in the presence of spiny lobsters: propensity to move (activity level), which can increase or decrease encounter rates with predators (Huey & Pianka, 1981;Skelly, 1994), and urchin's tendency to conceal themselves with substrate (covering behavior). Although the function of urchin covering behavior appears to vary among species (i.e., protection from wave action; Dumont, Drolet, Deschênes, & Himmelman, 2007), we predicted that urchins would be safer from predators while buried in substrate. ...
... Covering behavior resembles common metrics of "boldness" in the personality literature and has antipredator benefits in some species of urchins (Amsler, McClintock, & Baker, 1999). However, the behavior can be cued by wave action and sunlight in other urchin species (Dumont et al., 2007), although urchins deploy these behaviors in the absence of both (Pawson & Pawson, 2013). We examine here whether covering behavior might provide an antipredator benefit to purple urchins with predators during staged encounters. ...
Temporally consistent individual differences in behavior impact many ecological processes. We simultaneously examined the effects of individual variation in prey activity level, covering behavior, and body size on prey survival with predators using an urchin–lobster system. Specifically, we tested the hypothesis that slow‐moving purple sea urchins (Strongylocentrotus purpuratus) and urchins who deploy extensive substrate (pebbles and stones) covering behavior will out‐survive active urchins that deploy little to no covering behavior when pitted against a predator, the California spiny lobster (Panulirus interruptus). We evaluated this hypothesis by first confirming whether individual urchins exhibit temporally consistent differences in activity level and covering behavior, which they did. Next, we placed groups of four urchins in mesocosms with single lobster and monitored urchin survival for 108 hr. High activity level was negatively associated with survival, whereas urchin size and covering behavior independently did not influence survival. The negative effect of urchin activity level on urchin survival was strong for smaller urchins and weaker for large urchins. Taken together, these results suggest that purple urchin activity level and size jointly determine their susceptibility to predation by lobsters. This is potentially of great interest, because predation by recovering lobster populations could alter the stability of kelp forests by culling specific phenotypes, like foraging phenotypes, from urchin populations.
... Covering can provide sea urchins with protection from predators [16], mechanical damage (wave surge or floating debris) [11,17], overexposure to light [7], or can act as a food source [18]. However, no prior studies have considered a relationship between sea urchin biology and the reaction. ...
... Tripneustes and Lytechinus urchins primarily use the reaction to avoid bright light, but the importance of protection from wave surge has also been noted for both species [25,33]. Strongylocentrotus urchins cover to shield themselves from light and use covering as a food source, but one study has also suggested the behavior might be used to prevent mechanical damage [17]. Because of this, it remains difficult to determine the reasons for a species cryptic behavior by any means apart from running experiments on the species in question. ...
... Echinoid covering behavior is considered to be a reflexive response (Lawrence 1976a, Pawson & Pawson 2013 and references within), yet there are likely both abiotic and biotic factors involved (Verling et al. 2004, Dumont et al. 2007, Chen & Soong 2010, Pawson & Pawson 2013. Previous in situ studies on several species of shallow-water sea urchins have reported that the extent of covering material is positively associated with higher degrees of wave action, suggesting that sea urchins are capable of detecting high flow and adding additional covering materials to serve as ballast to prevent dislodgement of the individual from the substratum (James 2000, Dumont et al. 2007). ...
... Echinoid covering behavior is considered to be a reflexive response (Lawrence 1976a, Pawson & Pawson 2013 and references within), yet there are likely both abiotic and biotic factors involved (Verling et al. 2004, Dumont et al. 2007, Chen & Soong 2010, Pawson & Pawson 2013. Previous in situ studies on several species of shallow-water sea urchins have reported that the extent of covering material is positively associated with higher degrees of wave action, suggesting that sea urchins are capable of detecting high flow and adding additional covering materials to serve as ballast to prevent dislodgement of the individual from the substratum (James 2000, Dumont et al. 2007). Both tube feet and spines are involved in the righting response in L. variegatus (Lawrence 1976b). ...
Righting behavior has been used extensively in laboratory studies of sea urchins as an indicator of stress under various environmental conditions. In situ measurements of the natural righting response of sea urchins would serve to place such laboratory measurements in an ecological context as well as potentially validate laboratory control conditions. We investigated the righting response of the sea urchin Lytechinus variegatus in seagrass and sand bottom habitats of Saint Joseph’s Bay, Florida. Field-measured righting times (other than the exception mentioned below) in L. variegatus were similar to those measured in laboratory studies. Moreover, as seen in multiple sea urchin species in laboratory studies, smaller individuals exhibited significantly shorter righting times than larger individuals. Importantly, sea urchins lacking covering material (shell material, seagrass blades) that were placed on open sand patches took significantly longer to right than those with covering material placed on sand patches. Our field observations indicate the importance of sea urchin size, substrate type, and the presence or absence of covering materials when making righting measurements in the laboratory or the field. Our findings also suggest that higher water velocities facilitate righting, as at higher flows on sand patches, the presence/absence of covering material no longer significantly impacted righting time. These findings are ecologically important as they indicate that, under certain natural conditions (sand substrate, low availability of covering materials and low water velocities), L. variegatus that are displaced onto their aboral side are more vulnerable to predation.
... Such 'covering behavior' is well documented in echinoids across a wide range of temperate and tropical shallow marine habitats, including rocky shores (Paracentrotus livi dus; Barnes & Crook 2001), seagrass beds (Lyte chinus variegatus, Amato et al. 2008; Tripneustes ventricosus, Kehas et al. 2005), tidepool boreholes (Strongylocentrotus purpuratus and Paracentrotus livi dus; Verling et al. 2004), and rhodolith beds (Toxo pneustes roseus; James 2000). Covering behavior could play a variety of functional roles, including protection from ultraviolet (UV) radiation (Millott 1956, Adams 2001, Kehas et al. 2005, prevention of dislodgement under high wave surge (Levin et al. 2001, Dumont et al. 2007 and predator avoidance (Agatsuma 2001, Amsler et al. 1999. For example, when juvenile Strongylocentrotus intermedius were exposed in laboratory experiments to the predatory crab Pugettia quadridens, echinoids that were of fered shells to cover themselves were more likely to survive than echinoids not offered shells (Agatsuma 2001). ...
... Echinoids in deeper water (1000−1500 m) displayed covering behavior significantly more frequently than those at shallower depths (390−500 m). Al though our study did not measure UV radiation or current speed, both of which can affect covering behavior in shallow-water echinoids (Adams 2001, Levin et al. 2001, Kehas et al. 2005, Dumont et al. 2007, it is unlikely that either of these factors would have affected echinoids living in the deep sea more so than those living at shallower depths. In the Southern Ocean, biologically relevant levels of UV-B radiation only extend down to 30 m (Karentz 1994), and currents in our images appeared relatively weak. ...
Covering behavior refers to the propensity of echinoids (Echinoidea) to lift materials from the surrounding environment onto their aboral surfaces using their tube feet and spines. This behavior has been widely documented in regular echinoids from a variety of well-lit, shallow- marine habitats. Covering behavior in the deep sea, however, is rarely observed, and the functional significance of covering when it does occur remains speculative. During a photographic survey of the seafloor off Anvers Island and Marguerite Bay along the western Antarctic Pen - insula, we imaged 11 benthic transects at depths ranging from 390 to 2100 m. We recorded the number of echinoid species, incidence of covering behavior, types of materials used for covering, potential predators of echinoids, and potential prey items for predators. The echinoid Sterechinus spp. was found at all depths, and the percentage of individuals exhibiting covering behavior increased with depth between 390 and 1500 m. There was a significant positive correlation between the incidence of covering behavior in Sterechinus spp. and the density of king crabs (Anomura: Lithodidae), crushing predators that may be expanding their bathymetric range up the Antarctic continental slope as a consequence of ongoing climatic warming. In contrast, covering behavior was not positively correlated with the densities of non-crab predators, the total densities of predators, or the availability of prey. Our results document rarely observed covering behavior in echinoids living in the deep sea and suggest that covering could be a behavioral response to predation pressure by king crabs.
... Covering behavior, which is exhibited in species from both shallow (Verling et al., 2002) and deep (Pawson and Pawson, 2013) environments, refers to sea urchins using their tube feet and spines to move objects, such as shells, stones and algae fragments, onto their dorsal surface. A number of hypotheses have been tested to explain the evolutionary drives of covering behavior (Crook, 2003), including protection against exposure to solar radiation (Adams, 2001;Kehas et al., 2005;Dumont et al., 2007;Sigg et al., 2007), predation (Amsler et al., 1999;Agatsuma, 2001), desiccation (Orton, 1929), wave surge (Millott, 1976) and fl oating sand (Richner and Milinski, 2000), or/and as a refl exive action (Dambach and Hensel, 1970;Lawrence, 1976). Although it is considered that covering behavior is a behavioral avoidance strategy against UV radiation (Lamare et al., 2011), the fi tness benefi ts of this behavior remains largely unknown. ...
... Although a number of environmental factors have been proposed to explain covering (Dumont et al., 2007;Lamare et al., 2011;Chang et al., 2013) and righting behaviors (Lawrence, 1975), little information is available about the fi tness-related basis of these Table 2 for abbreviations of TC-1, TC-2, NS-1 and NS-2. ...
Complex marine benthic environments shape a number of ecologically important behaviors in sea urchins, including covering and righting behaviors. The present study correlated covering and righting behaviors to a series of fitness-related traits in sea urchins. Righting response time of Glyptocidaris crenularis was significantly positively correlated with body size, but significantly negatively correlated with food consumption. Covering behavior was not significantly correlated with test diameter, test height or body weight, but covering response time was negatively correlated with body weight. A significantly negative correlation was found between righting response time and covering response time. Glyptocidaris crenularis showed a significantly positive correlation in covering response time with and without exposure to poured sand, but no significance in covering ability (number of shells used to cover). The present study provides new insight into internal mechanisms and evolutionary drives of covering and righting behaviors of sea urchins.
... For behavioral assessments, we used the righting ability which is the most studied and relevant sea urchin behavior as it evaluates the animal's capacity to readjust its position after being knocked over by physical turbulence and to escape predators (Brothers & McClintock, 2015;Dumont et al., 2007). We also tested potential effects on urchins' metabolomic profiles (Hollywood et al., 2006;Wang et al., 2019) targeting the gonad, as it is the major nutrient storage organ (Byrne & Sewell, 2019). ...
Salmon aquaculture is a major economic activity in Atlantic Canada. The anti-sea lice therapeutant emamectin benzoate (EMB) and the antibiotic oxytetracycline (OTC) are widely used in aquaculture and are detected in sediments around sites. The green sea urchin Strongylocentrotus droebachiensis is an important benthic species in Canada that may be exposed to these compounds including organic matter near aquaculture sites. A central composite rotatable design was applied to investigate the potential effect of contaminant mixtures on adult green sea urchins during a 140-day exposure to environmentally relevant concentrations of EMB, OTC, and organic matter (OM). Endpoints considered in this study included behavior (righting time) assessed every two weeks, immunology (coelomocyte characteristics and functionality) and gonadosomatic index (GSI) investigated at the end of the exposure. Metabolomic profiling was also carried out in the gonad tissue at the end of the exposure. Two test conditions were found to impact coelomocyte number and cell viability, but immunology fully recovered 80 days post-exposure. No other clear trends in the effect of EMB, OTC, and OM were found on other sea urchin immunological endpoints, nor righting time, GSI or metabolites concentrations. Our results suggest that there is no clear impact of the contaminant mixtures tested on urchins though interactions suggest complex mechanisms that require further testing.
... Echinoderms exhibit many interesting behaviors. Covering (securing items like algae, marine debris, and shells with their tube feet) is commonly used by echinoids (sea urchins) as camouflage [80][81][82]. In laboratory experiments, urchins exposed to higher water temperatures were less likely to cover, and if they did, the process took longer [82]. ...
Simple Summary
Invertebrates (animals without backbones) make up over 95% of the earth’s species yet compared with vertebrates (animals with backbones like fishes, amphibians, reptiles, birds, and mammals) our understanding of and efforts relating to the topic of welfare is relatively minimal. We have selected seven of the most economically important and widely recognized invertebrate taxa to focus the topic of animal welfare on. In these pages the reader will learn about coelenterates (jellyfishes, anemones, and corals), mollusks (snails, slugs, squid, and octopi), crustaceans (lobsters, crabs, and shrimp), echinoderms (sea stars, sea urchins, and sea cucumbers), chelicerates (spiders, scorpions, and horseshoe crabs), myriapods (centipedes and millipedes), and insects (butterflies, honeybees, and fruit flies). In addition to discussing the welfare of these species, other topics, including anatomy, physiology, husbandry, natural history, and environmental diseases, are reviewed.
Abstract
Invertebrates are a diverse group of animals that make up the majority of the animal kingdom and encompass a wide array of species with varying adaptations and characteristics. Invertebrates are found in nearly all of the world’s habitats, including aquatic, marine, and terrestrial environments. There are many misconceptions about invertebrate sentience, welfare requirements, the need for environmental enrichment, and overall care and husbandry for this amazing group of animals. This review addresses these topics and more for a select group of invertebrates with biomedical, economical, display, and human companionship importance.
... Light intensity is a critical factor that influences the behavior of echinoderms. A previous study reported that sea urchins exhibited negative phototaxis and covering behavior to avoid high-intensity light and ultraviolet light (Adams, 2001;Crook et al., 1999;Dumont et al., 2007). Moreover, the sea cucumber Apostichopus japonicus exhibited variations in the tolerance to light intensity (Lin et al., 2013). ...
... UVB radiation is an abiotic factor known to control the distribution and abundance of different marine organisms in a bathymetric profile due to its negative effects on cells, with physiological and behavioral consequences [42]. Evasive responses to UVR include habitat selection processes [43,44], vertical/horizontal migration in the water column [45], burial in the sediment [46] and body covering with physical structures that minimize damage induced by direct or indirect exposure [47,48]. UVR evasive responses described previously in sea anemones include covering the body column with either gravel or debris and contraction of its body column [49]. ...
Anthopleura hermaphroditica is an intertidal anemone that lives semi-buried in soft sediments of estuaries and releases its brooded embryos directly to the benthos, being exposed to potentially detrimental ultraviolet radiation (UVR) levels. In this study, we investigated how experimental radiation (PAR: photosynthetically active radiation; UVA: ultraviolet A radiation; and UVB: ultraviolet B radiation) influences burrowing (time, depth and speed) in adults and juveniles when they were exposed to PAR (P, 400–700 nm), PAR + UVA (PA, 315–700 nm) and PAR + UVA + UVB (PAB, 280–700 nm) experimental treatments. The role of sediment as a physical shield was also assessed by exposing anemones to these radiation treatments with and without sediment, after which lipid peroxidation, protein carbonyls and total antioxidant capacity were quantified. Our results indicate that PAB can induce a faster burial response compared to those anemones exposed only to P. PAB increased oxidative damage, especially in juveniles where oxidative damage levels were several times higher than in adults. Sediment offers protection to adults against P, PA and PAB, as significant differences in their total antioxidant capacity were observed compared to those anemones without sediment. Conversely, the presence or absence of sediment did not influence total antioxidant capacity in juveniles, which may reflect that those anemones have sufficient antioxidant defenses to minimize photooxidative damage due to their reduced tolerance to experimental radiation. Burrowing behavior is a key survival skill for juveniles after they have been released after brooding.
... The covering behaviour consists of taking ambient elements (small rocks, shells or algae) with the tube feet to cover the aboral surface [111,112]. Sea urchin righting, covering and shelter-seeking behaviours enable the animal to escape from predators, reach crevices or seagrass meadows, prevent the occlusion of the apical openings of the water vascular system (madreporite) and seek protection from solar radiation and physical turbulence [113][114][115][116][117][118]. Investigating the possible impacts of acidification on behavioural endpoints could help to predict the sea urchins' responses in an acidification scenario as ecosystem engineers. ...
The continuous release of CO2 in the atmosphere is increasing the acidity of seawater worldwide, and the pH is predicted to be reduced by ~0.4 units by 2100. Ocean acidification (OA) is changing the carbonate chemistry, jeopardizing the life of marine organisms, and in particular calcifying organisms. Because of their calcareous skeleton and limited ability to regulate the acid–base balance, echinoids are among the organisms most threatened by OA. In this review, 50 articles assessing the effects of seawater acidification on the echinoid adult stage have been collected and summarized, in order to identify the most important aspects to consider for future experiments. Most of the endpoints considered (i.e., related to calcification, physiology, behaviour and reproduction) were altered, highlighting how various and subtle the effects of pH reduction can be. In general terms, more than 43% of the endpoints were modified by low pH compared with the control condition. However, animals exposed in long-term experiments or resident in CO2-vent systems showed acclimation capability. Moreover, the latitudinal range of animals’ distribution might explain some of the differences found among species. Therefore, future experiments should consider local variability, long-term exposure and multigenerational approaches to better assess OA effects on echinoids.
... For example, decorator crabs collect elements from the environment to cover themselves, likely gaining physical protection and reducing detection by predators (Hultgren & Stachowicz, 2009;Ruxton & Stevens, 2015). Similar patterns have been documented for other aquatic fauna such as sea urchins, brachyuran, hermit crabs, and caddisfly larvae (Ross, 1971;Wicksten, 1986;Otto, 2000;Dumont et al., 2007). Comparable uses of external materials for decoration have been explored for terrestrial animals, mostly among larvae of several insect species (Nakahira & Arakawa, 2006;Jackson & Pollard, 2007;Khan, 2020). ...
Many ecological interactions of spiders with their potential prey and predators are affected by the visibility of their bodies and silk, especially in habitats with lower structural complexity that expose spiders. For instance, the surface of tree trunks harbours relatively limited structures to hide in and may expose residents to visual detection by prey and predators. Here we provide the first detailed description of the novel retreat building strategy of the tree trunk jumping spider Arasia mullion . Using fields surveys, we monitored and measured over 115 spiders and 554 silk retreats. These spiders build silk retreats on the exposed surface of tree trunks, where they remain as sedentary permanent residents. Furthermore, the spiders decorate the silk retreats with bark debris that they collect from the immediate surrounding. We discuss the role of silk decoration in the unusual sedentary behaviour of these spiders and the potential mechanisms that allow A. mullion to engineer their niche in a challenging habitat.
... Covering behaviour and righting response have been regarded as indicators of biocompatibility in organisms exposed to environmental stress (Brothers and McClintock 2015). The covering behaviour of sea urchin serves an important biological function for self-protection from environmental stress (Agatsuma 2001;Dumont et al. 2007;Ling and Johnson 2012). In this study, we found that exposure to stranded HFO caused a decrease in the number of shells covering sea urchins in a dose-dependent manner, thereby reducing their fitness and biological functions. ...
In this study, we investigated the behavioural, morphological and physiological responses of the sea urchin (Strongylocentrotus intermedius) after subacute exposure to stranded heavy fuel oil (HFO) at oil loadings of 600, 1200, 2400 and 4800 μg oil g⁻¹ gravel for 21 days. No significant differences in the survival rate and body size of S. intermedius were found following subacute exposure to stranded HFO at various oil loadings. Differently, the food consumption, covering behaviour, righting response and gonadosomatic index (GSI) showed obvious adverse effects at higher oil loadings, manifested as a low level of food consumption, reduced covering ability, slower righting speed and decreased GSI compared with the control. This study indicated that subacute exposure to the stranded HFO could cause an adverse effect on the fitness-related traits of sea urchins and provide new insights into the impact of oil spill pollution on benthic organisms.
... Opsin2 and Opsin5 have been found only in echinoderms; therefore, they are thought to be specific to the group. Because some of the expression patterns of these genes have been reported in both embryos/larvae and adults [24][25][26][27], it is reasonably expected that sea urchins have the ability to react to light stimuli from a genomic perspective, as reported in adult behavioral studies [28,29]. However, the functions of photoreceptor genes have never been confirmed by using genetic modification except for the function of the recently reported gut-regulatory Go-Opsin [12], and the neural pathway regulating cilia-based larval behavior has not yet been identified. ...
To survive, organisms need to precisely respond to various environmental factors, such as light and gravity. Among these, light is so important for most life on Earth that light-response systems have become extraordinarily developed during evolution, especially in multicellular animals. A combination of photoreceptors, nervous system components, and effectors allows these animals to respond to light stimuli. In most macroscopic animals, muscles function as effectors responding to light, and in some microscopic aquatic animals, cilia play a role. It is likely that the cilia-based response was the first to develop and that it has been substituted by the muscle-based response along with increases in body size. However, although the function of muscle appears prominent, it is poorly understood whether ciliary responses to light are present and/or functional, especially in deuterostomes, because it is possible that these responses are too subtle to be observed, unlike muscle responses. Here, we show that planktonic sea urchin larvae reverse their swimming direction due to the inhibitory effect of light on the cholinergic neuron signaling>forward swimming pathway. We found that strong photoirradiation of larvae that stay on the surface of seawater immediately drives the larvae away from the surface due to backward swimming. When Opsin2, which is expressed in mesenchymal cells in larval arms, is knocked down, the larvae do not show backward swimming under photoirradiation. Although Opsin2-expressing cells are not neuronal cells, immunohistochemical analysis revealed that they directly attach to cholinergic neurons, which are thought to regulate forward swimming. These data indicate that light, through Opsin2, inhibits the activity of cholinergic signaling, which normally promotes larval forward swimming, and that the light-dependent ciliary response is present in deuterostomes. These findings shed light on how light-responsive tissues/organelles have been conserved and diversified during evolution.
... Sea urchins can move in the surrounding area while grazing, looking for food sources, mates, refuges or protection from severe currents (Boudouresque and Verlaque, 2020;Cohen--Rengifo et al., 2019;Dance, 1987;Stewart and Britton-Simmons, 2011), even if they demonstrate overall site fidelity (Dance, 1987;Migliaccio et al., 2019). Sea urchin righting and sheltering behaviours enable the animal to escape from predators, solar radiation and physical turbulence (Brothers and McClintock, 2015;Dumont et al., 2007;Pinna et al., 2012). Very few studies analysed the influence of environmental variability on sea urchin behaviour, namely Cohen-Rengifo et al. (2017, Morse and Hunt (2013) and Zhang et al. (2017); even fewer were carried out under predicted acidification conditions, namely Challener and McClintock (2013), Emerson et al. (2017) and Marčeta et al. (2020). ...
CO2-driven ocean acidification affects many aspects of sea urchin biology. However, even in the same species, OA effects are often not univocal due to non-uniform exposure setups or different ecological history of the experimental specimens. In the present work, two groups of adult sea urchins Paracentrotus lividus from different environments (the Lagoon of Venice and a coastal area in the Northern Adriatic Sea) were exposed to OA in a long-term exposure. Animals were maintained for six months in both natural seawater (pHT 8.04) and end-of-the-century predicted condition (-0.4 units pH). Monthly, physiological (respiration rate, ammonia excretion, O:N ratio) and behavioural (righting, sheltering) endpoints were investigated. Both pH and time of exposure significantly influenced sea urchin responses, but differences between sites were highlighted, particularly in the first months. Under reduced pH, ammonia excretion increased and O:N decreased in coastal specimens. Righting and sheltering were impaired in coastal animals, whereas only righting decreased in lagoon ones. These findings suggested a higher adaptation ability in sea urchins from a more variable environment. Interestingly, as the exposure continued, animals from both sites were able to acclimate. Results revealed plasticity in the physiological and behavioural responses of sea urchins under future predicted OA conditions.
... Here, under laboratory conditions, we describe a novel behaviour whereby hungry green sea urchins actively attacked and consumed multiple sea stars, Crossaster papposus (a known predator of S. drobachiensis; Himmelman & Dutil, 1991;Gaymer et al., 2004;Dumont et al., 2007), in a predictive behavioural fashion which we term "urchin pinning." ...
Green sea urchins (Strongylocentrotus droebachiensis) are dominant components in benthic ecosystems that form aggregations and can transform entire kelp forests into barren systems. While these urchins are known to unwittingly consume practically anything in their path while grazing, detailed descriptions of active predatory behaviour on known predators (i.e., predator-prey reversal) are undocumented. Here, we use laboratory observations to describe the behavioural tactics used by starved S. droebachiesis to actively attack and consume sea stars, Crossaster papposus-a known predator of S. droebachiensis. We observed urchins preying on three separate sea stars, with one being substantially consumed by urchins within 24 h. Urchins exhibited a direct mode of attack on sea stars by individually mounting and consuming the tips of the arms. Interestingly, we did not observe any conflict between individual urchins for attacking the sea star despite there being ≈80 starving urchins in the tank (and only 10-12 arms on the sea stars). Some sea stars did not attempt to escape urchin predation at all, while others attempted to escape by fleeing and lifting arms on top of the urchins. Given that sensory perception in sea stars is largely derived from the arm tips, we suggest that urchins directly attack and consume many sea star arm tips in an attempt to "pin" sea stars before consuming them. As such, we term this predatory behaviour "urchin pinning". These observations ultimately provide the first detailed behavioural documentation of how urchins actively prey on a known predator and provide a basis for a wealth of future research.
... Covering (securing items like algae, shells, debris with tube feet) is commonly used by echinoids (sea urchins) to hide or camouflage themselves. [100][101][102] In the laboratory, urchins exposed to increased water temperature were less likely to cover, and when they did, the process was prolonged. 102 These investigators also investigated 2 other urchin behaviors: sheltering and righting. ...
Invertebrate animals comprise more than 95% of the animal kingdom's species and approximately 40 separate phyla. Yet, invertebrates are an artificial taxon, in which all members simply possess a single negative trait: they lack a vertebral column (backbone). In fact, some invertebrates are more closely related to vertebrates than to their "fellow" invertebrates. For the purpose of this veterinary article, we have elected to review a handful of important groups: Coelenterates, Gastropods, Cephalopods, Chelicerates, Crustaceans, Insects, and Echinoderms. We have primarily included behaviors that may have an impact on clinical case outcome, or be of interest to the veterinary clinician.
... Le comportement est souvent étudié afin d'estimer l'état de santé des échinodermes (Dumont et al., 2007;Percy, 1973). Parmi ces indicateurs comportementaux, le temps de retournement est couramment étudié puisqu'il est en relation avec la coordination du système neuromusculaire en réponse à un changement d'orientation (Kleitman, 1941) et reflète, par exemple, la capacité d'un oursin à survivre, une fois déplacés par un prédateur (Percy, 1973). ...
Les microalgues toxiques sont connues pour produire un grand nombre de métabolites, dont les effets sur l’environnement demeurent relativement méconnus à ce jour. Dans ce contexte, le travail présenté ici s’est focalisé sur l’écologie chimique du dinoflagellé benthique toxique Ostreopsis cf. ovata en Méditerranée nord occidentale. Dans un premier temps, un suivi de l’abondance cellulaire d’O. cf. ovata sur les substrats biotiques (macroalgues) ainsi que dans la colonne d’eau, a été réalisé à différentes échelles de temps et d’espace, permettant de confirmer la nature tychoplanctonique de ce dinoflagellé. En raison de ces migrations journalières, il va donc impacter aussi bien les écosystèmes benthiques que planctoniques. Afin d’étudier les interactions qu’O. cf. ovata entretient avec son environnement au cours de ces différentes phases, nous avons évalué l’effet d’O. cf. ovata sur la survie, la croissance et le métabolisme secondaire de différents modèles biologiques incluant un compétiteur (diatomée) et plusieurs espèces de prédateurs directs (copépodes benthiques et planctoniques) et indirects (oursins) au cours d’analyses in situ et en laboratoire. Les suivis réalisés in situ et les expériences en laboratoire n’ont pas permis de mettre en évidence un effet néfaste d’O. cf ovata sur la physiologie et le comportement des oursins, suggérant que c’est l’hypoxie engendrée par les efflorescences d’O. cf. ovata qui est le facteur à l’origine des mortalités de masse d’invertébrés décrites en milieu naturel. En revanche, nos résultats montrent qu’O. cf. ovata impacte négativement la croissance des diatomées compétitrices, tandis que ces dernières inhibent en retour sa croissance et son efficacité photosynthétique. Concernant les interactions avec les copépodes, nos résultats montrent une réponse espèce-dépendante, avec en particulier un effet reprotoxique sur les copépodes benthiques. Afin d’analyser plus rapidement, facilement et de façon reproductible la toxicité des différentes souches d’O. cf. ovata ainsi que l’évolution de cette toxicité au cours d’une efflorescence, nous avons ensuite adapté à ce dinoflagellé un test de toxicité utilisant le crustacé Artemia fransciscana. Enfin, ces expérimentations ont été couplées à une approche métabolomique qui a permis d’étudier la nature des métabolites secondaires produits par O. cf ovata. Parmi ces métabolites, les toxines semblent participer aux interactions biotiques mises en évidences au cours des expériences décrites précédemment. En outre, nos résultats suggèrent que d’autres métabolites, dont la nature n’est pas encore connue, contribuent également à l’écologie chimique de cette espèce. En conclusion, notre travail montre qu’O. cf. ovata, par la récurrence de ses efflorescences, sa nature tychoplanctonique, l’abondance et la diversité des métabolites secondaires qu’il produit, s’avère être un excellent modèle pour étudier l’écologie chimique des microalgues marines toxiques.
... These findings reflect the reality of life: human behaviour is complex and necessarily always results from the combination of a myriad of factors-some more influential than others, but all factors acting in concert with each other. Given that multiple, reciprocal factors are needed to explain the behaviour of even simple creatures like sea urchins (Dumont, Drolet, Deschenes, & Himmelman, 2007) Clayton and Karazsia's (2020) findings that a general connection with nature was strongly associated with behavioural engagement in pro-environmental activities such as recycling, turning off lights, and overall reduction of behaviours that contribute to climate change. Combined, these findings are in line with the argument, put forth by several researchers, that engagement in pro-nature behaviours is motivated by feeling connected to nature (Frantz & Mayer, 2014;Kossack & Bogner, 2012;Otto et al., 2014;Roczen et al., 2014). ...
The biodiversity crisis demands greater engagement in pro‐nature conservation behaviours. Research has examined factors which account for general pro‐environmental behaviour; that is, behaviour geared to minimizing one's impact on the environment. Yet, a dearth of research exists examining factors that account for pro‐nature conservation behaviour specifically—behaviour that directly and actively supports conservation of biodiversity.
This study is the first of its kind to use a validated scale of pro‐nature conservation behaviour. Using online data from a United Kingdom population survey of 1,298 adults (16+ years), we examined factors (composed of nine variable‐blocks of items) that accounted for pro‐nature conservation behaviour.
These were: individual characteristics (demographics, nature connectedness), nature experiences (time spent in nature, engaging with nature through simple activities, indirect engagement with nature), knowledge and attitudes (knowledge/study of nature, valuing and concern for nature) and pro‐environmental behaviour.
Together, these explained 70% of the variation in people's actions for nature.
Importantly, in a linear regression examining the relative importance of these variables to the prediction of pro‐nature conservation behaviour, time in nature did not emerge as significant.
Engaging in simple nature activities (which is related to nature connectedness) emerged as the largest significant contributor to pro‐nature conservation behaviour. Commonality analysis revealed that variables worked together, with nature connectedness and engagement in simple activities being involved in the largest portion of explained variance.
Overall, findings from the current study reinforce the critical role that having a close relationship with nature through simple everyday engagement plays in pro‐nature conservation behaviour. Policy recommendations are made.
A free Plain Language Summary can be found within the Supporting Information of this article.
... Sea urchins, in particular, are well known for their morphological, physiological and behavioral plasticity (i.e. Adams et al., 2011;Crook and Davoren, 2016;Dumont et al., 2007;Ebert, 1996;Haag et al., 2016;Harding and Scheibling, 2015;Russell, 1998;Urriago et al., 2011). Benthic (juveniles, adults) and pelagic (larvae) stages show rapid morphological response of hard structures to food availability (i.e. ...
... Sea urchins, in particular, are well known for their morphological, physiological and behavioral plasticity (i.e. Adams et al., 2011;Crook and Davoren, 2016;Dumont et al., 2007;Ebert, 1996;Haag et al., 2016;Harding and Scheibling, 2015;Russell, 1998;Urriago et al., 2011). Benthic (juveniles, adults) and pelagic (larvae) stages show rapid morphological response of hard structures to food availability (i.e. ...
... In this sense, food limitation induces longer post-oral arm length, both absolutely and relative to body rod length (Adams et al., 2011;McAlister & Miner, 2018). Because in order to avoid UV-B radiation, covering and shading behaviors of sea urchins may reduce movement and hence the ability of feeding (Kehas, Theoharides & Gilbert, 2005;Dumont et al., 2007;Burnaford & Vasquez, 2008). In the present study, post-oral arm length/body rod length significantly increased in larvae whose parents were exposed to short-term UV-B radiation, indicating a positive transgenerational effect. ...
Transgenerational effects are important for phenotypic plasticity and adaptation of marine invertebrates in the changing ocean. Ultraviolet-B (UV-B) radiation is an increasing threat to marine invertebrates. For the first time, we reported positive and negative transgenerational effects of UV-B radiation on egg size, fertilization, hatchability and larval size of a marine invertebrate. Strongylocentrotus intermedius exposed to UV-B radiation showed positive transgenerational effects and adaptation on egg size, hatching rate and post-oral arm length of larvae. Negative transgenerational effects were found in body length, stomach length and stomach width of larvae whose parents were exposed to UV-B radiation. Sires probably play important roles in transgenerational effects of UV-B. The present study provides valuable information into transgenerational effects of UV-B radiation on fitness related traits of sea urchins (at least Strongylocentrotus intermedius ).
... Decoration camouflage, in which animals attach material (organisms or debris) from the environment to their bodies, is not limited to decorator crabs; it is used by nearly 25% of metazoan phyla 29 and is an effective strategy for avoiding predation and increasing survival 30 . Decoration behavior is considered to be energetically expensive to maintain, requiring that animals expend energy to find and manipulate decorations, as well as place and carry these decorations on their bodies 29,31,32 . Augmenting the costs of active decorating are the costs that come with developing the morphology for decoration attachment, such as setae and adhesives 28 . ...
Many marine calcifiers experience metabolic costs when exposed to experimental ocean acidification conditions, potentially limiting the energy available to support regulatory processes and behaviors. Decorator crabs expend energy on decoration camouflage and may face acute trade-offs under environmental stress. We hypothesized that under reduced pH conditions, decorator crabs will be energy limited and allocate energy towards growth and calcification at the expense of decoration behavior. Decorator crabs, Pelia tumida, were exposed to ambient (8.01) and reduced (7.74) pH conditions for five weeks. Half of the animals in each treatment were given sponge to decorate with. Animals were analyzed for changes in body mass, exoskeleton mineral content (Ca and Mg), organic content (a proxy for metabolism), and decoration behavior (sponge mass and percent cover). Overall, decorator crabs showed no signs of energy limitation under reduced pH conditions. Exoskeleton mineral content, body mass, and organic content of crabs remained the same across pH and decoration treatments, with no effect of reduced pH on decoration behavior. Despite being a relatively inactive, osmoconforming species, Pelia tumida is able to maintain multiple regulatory processes and behavior when exposed to environmental pH stress, which underscores the complexity of responses within Crustacea to ocean acidification conditions.
... Ultraviolet radiation induces signifi cant negative phototaxis (for example, sheltering behavior) and covering behavior of sea urchins (Adams, 2001; Verling et al., 2002;Dumont et al., 2007;Sigg et al., 2007). These behaviors are potentially important to their fi tness (Zhao et al., 2016). ...
Ozone depletion induced by anthropogenic gases has been increasing the transmission of solar ultraviolet-B radiation (UV-B, 280–315 nm) through the atmosphere, which may impact the fitness of marine invertebrates in intertidal and shallow waters. To our knowledge, however, the responses of fitness related behaviors to UV-B radiation at different intensities have been rarely studied in marine invertebrates. For the first time, the present study investigated the effects of exposure of one hour to UV-B radiation at different intensities on foraging behavior, Aristotle’s lantern reflex and righting behavior of the sea urchin Strongylocentrotus intermedius. Exposure of one hour to UV-B radiation at 10 μW/cm² significantly reduced foraging behavior. An intensity dependent effect of exposure to UV-B radiation was found in the duration of the Aristotle’s lantern reflex. Exposure to UV-B radiation at 20 μW/cm² for one hour significantly reduced the duration of the Aristotle’s lantern reflex, but 10 μW/cm² did not. There was no significant difference of righting response time among sea urchins exposed to 0, 10 and 20 μW/cm² for one hour. To test potential carryover effects, the behavioral traits were re-measured three days later. We found significant carryover effects of UV-B radiation on foraging time and righting response time, but not on the duration of the Aristotle’s lantern reflex. The present study indicates that a brief exposure of one hour to UV-B radiation can significantly affect the duration of Aristotle’s lantern reflex, righting response time and foraging behavior of a sea urchin, although the immediate impacts and carryover effects were highly trait dependent. This study provides new information into the behavioral responses of marine invertebrates to exposure to UV-B radiation. Future studies should be carried out to investigate long-term carryover effects of UV-B radiation on behavioral and physiological fitness related traits.
... Spines and tube feet act together to select covering material and to transport it from the sea-bed up and onto the body of the animal (Figure 1). Different species of echinoids use different types of covering materials, including plant material, coral rubble, and calcium carbonate based shell fragments [48,49]. Some species drop these fragments at night and collect other fragments the next day. ...
Neuromorphic engineering is the approach to intelligent machine design inspired by nature. Here, we outline possible robotic design principles derived from the neural and motor systems of sea urchins (Echinoida). Firstly, we review the neurobiology and locomotor systems of sea urchins, with a comparative emphasis on differences to animals with a more centralized nervous system. We discuss the functioning and enervation of the tube feet, pedicellariae, and spines, including the limited autonomy of these structures. We outline the design principles behind the sea urchin nervous system. We discuss the current approaches of adapting these principles to robotics, such as sucker-like structures inspired by tube feet and a robotic adaptation of the sea urchin jaw, as well as future directions and possible limitations to using these principles in robots.
... Sea urchin species such as Lytechinus variegatus (Lamarck, 1816) (Fig. 3g) and Tripneustes ventricosus (Lamarck, 1816) (Table S2) have been found covered by ML in the Todos os Santos Bay, Brazil, a known area of high concentration of ML (de Carvalho-Souza and Tinôco, 2011). Sea urchins are known to cover themselves with substrate materials as protection against mechanical injuries associated with abrasion, dislodging, and UV radiation (Dumont et al., 2007). The use of these materials varies according to local availability, although selectivity is described for some species such as L. variegatus and T. ventricosus (Amato et al., 2008). ...
... Carrier shells (Xenophoridae) cement other, empty shells to their own shell. In the green sea urchin (Strongylocentrotus droebachiensis) protection against mechanical damage and UV light seems to be the driving force behind decoration behavior (Dumont et al., 2006), while predator avoidance seems to drive covering behavior in the sea urchin Sterechinus neumayeri (Amsler et al., 1999). ...
Bioaesthetics, an exciting new branch of aesthetics, examines the evolutionary origins of aesthetics in humans and other animals. We suggest that aesthetics is a multicomponent faculty and discuss certain traits that are shared with other species. We discuss Richard Prum's theory that aesthetic signal and audience are joined in a coevolutionary loop: one by necessity shaping the other. We discuss its implications for aesthetic phenomena as diverse as sexual selection, domestication, and cuisine. In addition to biologically evolved aesthetics, we emphasize that humans possess culturally coevolved aesthetics, which helps explain the unusual variability of aesthetic domains across human cultures. We analyze social and cognitive factors that may have driven this development, particularly exploring the role of the artist, who we argue must mentally adopt the position of the audience while producing an artwork, instantiating a third coevolutionary loop on the individual level.
... However, decorating may also play additional roles depending on an organism's environment. For instance, decorations could alter an organism's physical properties preventing dislodgement or provide a physical barrier preventing structural damage via abrasion or UV light (Dumont et al. 2007;Limm and Power 2011). The widespread evolution of decorating suggests it has clear benefits; however, investment in decorating is not without potential costs. ...
Although numerous aquatic and terrestrial species adorn their surface with items secured from their surroundings, termed decorating, the physical and environmental factors that drive this behavior are often unclear. One of the best-known examples of this phenomenon are the decorator crabs (Majoidea), with almost 75% of species known to decorate. Here, we examined patterns of decorating in a coral reef-associated majoid, Camposcia retusa, to identify what factors determine patterns of, and investment in, decorating. Observations of natural decoration patterns indicate this species primarily decorate with sponges, fleshy and filamentous algae, and detritus. Decorations were primarily distributed on the carapace and hind walking legs which may reflect exoskeleton morphology. However, decoration cover did not decline with size, as is observed in some other majoid species, suggesting the factors driving decoration investment remain consistent throughout growth stages. From behavioral experiments, we determined that nonuniform decorating is a result of active selection, with crabs preferentially decorating their hind legs and carapace, with only small items placed on the carapace. Decorating in C. retusa appears to function primarily as an antipredator response, with crabs decorating at higher rates when access to shelter is limited. This study is the first to quantify the decorating habits of C. retusa and suggests that behaviorally-mediated decorating has a primary antipredator function. This study also highlights the value of manipulative behavioral experiments as a tool for assessing the behavioral mechanisms that drive decorating in animals.
... Nevertheless, more studies are required for determining the food spectrum of the sea cucumbers because it is not precisely known (Calva 2003). Similarly, the sea urchin T. roseus was dominant on the rock and rubble coral, which could be explained by the cover of macroalgae, shells and other rubble, serving as camouflage against predators (Richner and Milinski 2000) and protection against excessive solar radiation (Sigg et al. 2007) and strong bottom currents (Dumont et al. 2007;Amato et al. 2008). Additionally, A. pulvinata was observed on the sand and rock coral, which could be related to its ingestion of deposit material from the bottom (as foraminifera and small gastropods) (De Ridder and Lawrence 1982). ...
Fourteen species of echinoderms and their relationships to the benthic structure of the coral reefs were assessed at 27 sites—with different levels of human disturbances—along the coast of the Mexican Central Pacific. Diadema mexicanum and Phataria unifascialis were the most abundant species. The spatial variation of the echinoderm assemblages showed that D. mexicanum, Eucidaris thouarsii, P. unifascialis, Centrostephanus coronatus, Toxopneustes roseus, Holothuria fuscocinerea, Cucumaria flamma, and Echinometra vanbrunti accounted for the dissimilarities among the sites. The spatial variation among the sites was mainly explained by the cover of the hard corals (Porites, Pocillopora, Pavona, Psammocora), different macroalgae species (turf, encrusting calcareous algae, articulated calcareous algae, fleshy macroalgae), sponges, bryozoans, rocky, coral rubble, sand, soft corals (hydrocorals and octocorals), Tubastrea coccinea coral, Balanus spp., and water depth. The coverage of Porites, Pavona, and Pocillopora corals, soft coral, rock, and Balanos shows a positive relationship with the sampling sites included within the natural protected area with low human disturbances. Contrary, fleshy macroalgae, sponges, and soft coral show a positive relationship with higher disturbance sites. The results presented here show the importance of protecting the structural heterogeneity of coral reef habitats because it is a significant factor for the distribution of echinoderm species and can contribute to the design of conservation programs for the coral reef ecosystem.
Despite the importance of flow velocity in marine ecosystems, molecular mechanisms of the water flow induced behavioral and growth changes remain largely unknown in sea urchins. The present study compared the gene expressions of the sea urchin Mesocentrotusnudus at high flow velocities (10 cm/s and 20 cm/s) and low flow velocity (2 cm/s) using transcriptomes. A total of 490 and 470 differentially expressed genes (DEGs) were discovered at 10 cm/s and 20 cm/s, respectively. There were 235 up-regulated and 255 down-regulated genes at 10 cm/s, 213 up-regulated and 257 down-regulated genes at 20 cm/s, compared with sea urchins at 2 cm/s. Further, there were 72 overlapped DEGs involved in regulation at both 10 cm/s and 20 cm/s. Gene Ontology (GO) functional annotation showed that DEGs were mainly enriched to cellular process, cell part, binding, and metabolism process. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis found that DEGs were enriched in three pathways related to amino acid metabolism and lipid metabolism. A number of genes related to growth and metabolism of sea urchins were mobilized in high flow velocity environment. We further highlighted a muscle-associated gene ankyrin-1, which is correlated with the movement of tube feet at different flow velocities. The present study provides valuable information on the molecular mechanisms of changed behaviors and growth when sea urchins are exposed to high flow velocity.
The effects of flow velocity on the fitness-related behaviours of Mesocentrotus nudus remain largely unknown, greatly hampering the efficiency of stock enhancement. To explore the appropriate velocities for stock enhancement, we investigated dislodgement and immobilization velocities up to 90 cm s ⁻¹ . The experimental results showed that M. nudus (test diameter of ~30 mm) were dislodged at 73.50 ± 7.7 cm s ⁻¹ and that M. nudus movement occurred only when the flow velocity was less than 33.40 ± 2.7 cm s ⁻¹ . Three flow velocities less than 33.40 ± 2.7 cm s ⁻¹ (2, 10 and 20 cm s ⁻¹ ) were subsequently used to study the effects of flow velocities on covering behaviour and the righting response time of M. nudus . The downstream movement velocity of M. nudus was significantly larger than that upstream at 2 cm s ⁻¹ ( P = 0.016) and 10 cm s ⁻¹ ( P = 0.008), but not at 20 cm s ⁻¹ ( P = 0.222). The righting response time of M. nudus was significantly longer at 20 cm s ⁻¹ than that at 2 cm s ⁻¹ ( P = 0.015). The present study indicates that a flow velocity less than 20 cm s ⁻¹ , preferably 2–10 cm s ⁻¹ , is probably appropriate for the stock enhancement of M. nudus . Notably, the current study is a laboratory investigation without considering the hydrographic complexity in the field. Further studies should be carried out to investigate the long-term effects of water flow on feeding and growth of M. nudus both in the laboratory and the field.
p> Paracentrotus gaimardi é um ouriço-do-mar conhecido por sua diversidade de cores, no entanto estudos abordando outros aspectos que não sua coloração ou reprodução são escassos. Assim, este estudo visa contribuir para uma melhor compreensão da biologia de P. gaimardi , fornecendo informações relevantes sobre seus hábitos comportamentais e alimentares. Seis indivíduos de duas colorações distintas foram coletados em São Paulo, sudeste do Brasil. Após sete dias de aclimatação, foram observados alguns aspectos comportamentais, bem como a preferência alimentar. Um notável comportamento de cobertura e uma aparente fototaxia negativa foi observado em todos os indivíduos estudados. Eles se alimentaram das algas Galaxaura sp., Padina sp. e Ulva lactuta , mas também foram observados predando a esponja Hymeniacidon heliophila e um espécime morto de Echinometra lucunter . Paracentrotus gaimardi é um herbívoro típico, alimentando-se principalmente de algas, semelhantemente ao já descrito para o seu congênere mediterrâneo P. lividus . Porém, P. gaimardi também foi observado alimentando-se diretamente de animais vivos e mortos, o que pode ser entendido como uma estratégia para obter nutrientes menos disponíveis no tecido de algas. As informações fornecidas neste estudo indicam que, de forma geral, a biologia de P. gaimardi é muito similar à de P. lividus , tornando pertinente comparações entre elas.
Palavras chave : Algas, comportamento de cobertura, esponja, predação.</p
This book is addressed to the readers operating in the sea urchin field of research, as well as to the lovers of this fascinating organism. Sea urchin, among the most known marine invertebrates belonging to the deuterostomes, is more closely related to humans than other invertebrates, thus representing a suitable model system not only for developmental biology and ecotoxicology but also for biomedicine. The topics described highlight the validity and versatility of this organism for different kinds of investigations. A collection of interesting chapters contributes to this volume and clearly shows the reason of the high interest manifested by a huge number of scientists around the world for this organism over time. Each contribution is a separate and comprehensive chapter but within the book's aim.
Increases in ocean temperature due to climate change are predicted to change the behaviors of marine invertebrates. Altered behaviors of keystone ecosystem engineers such as echinoderms will have consequences for the fitness of individuals, which are expected to flow on to the local ecosystem. Relatively few studies have investigated the behavioral responses of echinoderms to long-term elevated temperature. We investigated the effects of exposure to long-term (∼31 weeks) elevated temperature (∼3 • C above the ambient water temperature) on covering, sheltering and righting behaviors of the sea urchin Strongylocentrotus intermedius. Long-term elevated temperature showed different effects on the three behaviors. It significantly decreased covering behavior, including both covering behavior reaction (time to first covering) and ability (number of covered sea urchins and number of shells used for covering). Conversely, exposure to long-term elevated temperature significantly increased sheltering behavior. Righting response in S. intermedius was not significantly different between temperature treatments. The results provide new information into behavioral responses of echinoderms to ocean warming.
This review summarizes our knowledge of the effects of ultraviolet radiation (UVR) on Echinodermata, describing research undertaken over the past 100 years. These studies have shown that exposure of echinoderms to solar UVR can affect reproduction and development, change behavior, cause numerous biochemical and physiological changes, and increase mutation rates through DNA damage. These studies also describe mechanisms utilized by echinoderms to protect themselves against excessive UVR and subsequent damage, including sunscreens, antioxidants, cellular stress proteins, cell cycle genes and DNA repair. The many insightful studies on the effect of UVR on echinoderms that have been highlighted in the present review suggest that the phylum provides excellent model systems to further examine the role of UVR on marine species in a rapidly changing ocean.
Examination of the covering reaction (masking or heaping with shells) of Lytechinus anamesus in response to ultraviolet irradiation, sunlight, and surge suggests that most previous hypotheses explaining this reaction are inadequate or incomplete. Shaded L. anamesus initially reacts to short wavelength ultraviolet light (254 nm) with a fairly strong masking response, which is followed by death after an exposure of several days. Long wavelength ultraviolet light (360 mm) elicits moderate covering, while the nonirradiated controls rarely covered. These responses to ultraviolet light are probably artifacts, as L. anamesus and other sea urchins are seldom exposed to that factor in nature. There is a strong and immediate covering response to direct sunlight. Application of surge induces a cover response nearly equal to that of sunlight, regardless of light conditions. The intensity of covering during periods of surge appears to increase during the exposure period. Cessation of surge results in a rapid reduction in covering and a marked increase in movement. We suggest that covering is important in increasing the stability of this echinoid during periods of increased surge by effectively increasing its specific density, reducing its surface area, and changing the configuration it presents to surge forces. Sunlight intensity may be used as a cue that indicates directly the risk of displacement by surge action.
A specimen of the deep-water, spatangoid urchin, Cystochinusloveni, wearing a costume of agglutinated protists, was collected from 3088 m in the Gulf of Alaska, north-east Pacific. Over 24 putative taxa of living and dead foraminiferans and xenophyophores, as well as a sipunculan, polychaete, tanaid, and two isopods, were collected from the dorsal surface of this single individual. This is the first report of a deep-sea urchin using rhizopod protists and it is proposed that the urchin acquires camouflage or benefits from increased specific gravity associated with the protistan cloak.
Movement is likely a major factor contributing to the marked size partitioning of populations in relation to depth and habitat, as observed for many coastal invertebrates. Here, 2 approaches were used to examine the relationship of movement to size for the green sea urchin Strongylocentrotus droebachiensis on persistent urchin barrens in the northern Gulf of St. Lawrence, eastern Canada. The first approach involved quantifying the dispersal of tagged urchins from release points. Experiments were started by tagging all urchins in 1.0 m(2) plots with a fluorescent stain, then quantifying their abundance 9 or 40 d later in the release plots and at different distances from the release plots. The rate of dispersal of urchins from the plots varied greatly with size. In the initial plots, we recaptured 69% of <10 mm diameter urchins, compared to 2% for >15 mm diameter urchins, after 9 d, and 25 and 0%, respectively, after 40 d. In 5 of 6 trials executed, movement was directional, albeit in different directions in the different trials. The second approach evaluated urchin movement relative to size by quantifying the numbers of different-sized urchins moving into 1.0 m(2) circular plots, from which the natural population of urchins had been removed 48 h earlier. Trials were made either with or without algae in the center of the plots. After 48 h most urchins which had moved into the plots were large (>15 mm diameter). The movement of urchins was size-dependent, as the presence of algal food affected the rates of movement of large urchins into the plots, but had no detectable effect on small (<15 mm diameter) urchins. Both approaches demonstrated that urchins measuring <15 mm diameter (juveniles) have a relatively sedentary and cryptic lifestyle. Those >15 mm diameter showed increased movement, probably related to the search for food. This ontogenetic change in movement likely affects growth rates and contributes to size partitioning of urchin populations in different subtidal habitats.
We carried out experiments in a wave tank using a factorial design (in the presence and absence of waves and kelp blades) to evaluate the impact of water motion, and of wave-induced movement of kelp blades, on (1) movement of the predatory sea star Asterias vulgaris towards its prey, the blue mussel Mytilus edulis, and (2) on its success in capturing its prey. The wave tank mimicked the back-and-forth flow caused by waves. The displacement of the sea stars was 2 times greater in the absence than in the presence of waves. Movements of A. vulgaris were more directed towards the prey under back-and-forth water movement than under still conditions. The presence of kelp blades without waves also reduced the movement of sea stars towards prey as the sea stars largely stayed in the portion of the tank without kelp. Sea stars only became detached in treatments with waves, and a greater proportion detached when both waves and kelp were present. The success rate of sea stars in capturing mussels was null in the treatment with both waves and kelp. These observations support the hypothesis that the kelp canopy in shallow water, and movement of the kelp blades by waves, provide mussels with a spatial refuge from sea star predation. We show for the first time that a sea star can use distance chemodectection to localize prey under conditions of back-and-forth flow.
Spider crabs (family Majidae) often decorate themselves: that is, they put pieces of marine organisms among the hooked setae of the exoskeleton. This behavior can be absent in large crabs or those that live at great depths, on sand or in narrow crevices. Although some species put edible materials on their bodies and later remove and eat them, the majority of the spider crabs decorate themselves to camouflage themselves against predators. A model of the level of decoration is presented, from none at all to complete coverage of the dorsal surface. Important factors that affect the level are the evolutionary state, habitat, size, feeding and particularly the predators of the species of spider crab.
Background: Animals belonging to nearly 25% of the major metazoan phyla 'decorate' themselves with foreign material. Decoration occurs frequently in some taxa but infrequently in others. Some data indicate that decoration is a morphologically flexible phenotype that facilitates feeding and/or protects against biotic and abiotic forces. Yet decoration is not taxo-nomically ubiquitous. Other data suggest that decorating could be energetically costly. Questions: How do feeding, energy expenditure, and mortality risk interact to exert selective pressure on decorating phenotypes? Could energetic costs associated with decorating theoretically limit the behaviour's selective advantage and account for its patchy taxonomic distribution? Methods: Build a model of decoration's effect on reproductive potential using energy intake, energy expenditure, and mortality risk as parameters. Analytically find the upper bound of permissible energetic costs. From existing literature, estimate parameter values for energetics, reproduction, and mortality of the green sea urchin, Strongylocentrotus droebachiensis, and analyse them using graphical and numerical methods to determine the probable influence of energy cost on decoration in this animal. Conclusions: Physiologically realistic energetic costs can constrain the parameter space in which decorating is selectively advantageous. This appears to be true even for costs far below the theoretical upper limit. Thus the evolution of decoration should be more sensitive to energetic costs than to the other parameters that we modelled. Sensitivity to energetic costs may explain (at least in part) decoration's patchy taxonomic distribution.
Field observations and manipulative experiments in a nearshore cobble bed (2 to 3 m below mean low water) at Eagle Head, Nova Scotia, Canada, between 1984 and 1986, showed that small juveniles ofStrongylocentrotus droebachiensis (3 to 6 mm diam) sheltering beneath cobbles had a refuge from predators such as rock crabs, small lobsters, and fish. Sea urchins gradually outgrew these refuges and small adults (25 to 30 mm) required larger rocks as shelter from predators, particularly large cancrid crabs. Small juveniles were usually solitary and well dispersed beneath cobbles, whereas small adults tended to aggregate on the undersides and in the interstices of boulders. These aggregations may develop passively as sea urchins accumulate in suitablysized refuges. Chemotaxis experiments indicate that juvenileS. droebachiensis are repelled by waterborne stimuli from conspecifics. In a factorial experiment, effects of the presence of potential predators (rock crabs and lobsters) and/or food (kelp) on the behaviour of large juvenile (10 to 15 mm) and small adult sea urchins were examined in flowing seawater tanks. Both size classes formed exposed feeding aggregations when kelp was provided as food, irrespective of the presence or absence of predators. In the absence of kelp, each size class responded differently to the presence of a predator: juveniles became more cryptic, whereas adults aggregated on the tank sides. Increased movement to the sides of a tank in the presence of a predator may reflect a flight response, since chemotaxis experiments indicated thatS. droebachiensis is repelled by waterborne chemical stimuli from predators. Observational and experimental data suggest that predation at the late juvenile and early adult stages may influence population structure, distribution and abundance ofS. droebachiensis.
In North Carolina, the decorator crab Libinia dubia camouflages almost exclusively with the chemically noxious alga Dictyota menstrualis. By placing this alga on its carapace, the crab behaviorally sequesters the defensive chemicals of the plant and gains protection from omnivorous consumers. However, Dictyota is absent north of North Carolina, whereas Libinia occurs as far north as New England. Crabs from three northern locations where Dictyota is absent (Rhode Island, Connecticut, and New Jersey) camouflaged to match their environment, rather than selectively accumulating any one species. When D. menstrualis was offered to crabs from northern sites, they did not distinguish between it and other seaweeds for camouflage, whereas crabs from Alabama and two locations in North Carolina used D. menstrualis almost exclusively. In addition, in winter and spring, when Dictyota was seasonally absent in North Carolina, Libinia selectively camouflaged with the sun sponge Hymeniacidon heliophila, which was chemically unpalatable to local fishes. Thus, southern crabs were consistent specialists on chemically defended species for camouflage, while northern crabs were more generalized. The geographic shift in crab behavior away from specialization coincides with a reported decrease in both total predation pressure and the frequency of omnivorous consumers. These shifts in the nature and intensity of predation pressure may favor different camouflage strategies (generalist vs. specialist), contributing to the observed geographic differences in camouflage behavior. © 2000 The University of Chicago
Much literature in marine biology describes the extraordinary behaviour of sea urchins, e.g., Paracentrotus lividus, who cover their body with shells, stones and debris. The function of this strange behaviour, described as 'masking', is still a puzzle. Our experiment shows that sea urchins are loaded with more mussel shells when the delicate apical openings of their water vascular system which powers all their movements, are in danger of being occluded by floating sand. 'Masking' shells appear to function as an umbrella against floating particles.
Living echinoids provide a structural analogue to the rigid thecae of many extinct echinoderms and are here used to examine some consequences of the increased rigidity and decreased number of plates which occurred in several lineages of echinoderms. A special feature of the echinoids is the large spines which protect the echinoid tests from failure under impact. The spines absorb energy or spread loads because the spines break or the tissue connecting the spine to the test is stretched or torn. Spines that absorb impacts might be superfluous in echinoderms encased in a rigid test or theca if they have flexible stems or are in low energy habitats, but spines should be useful to stemless thecate echinoderms on hard substrata. In the absence of spines, a flexible theca of overlapping plates might be superior to a rigid theca. Greater rigidity does not necessarily provide greater protection.
Tracts of podial pores are sites of weakness in all tests examined [ Eucidaris tribuloides (Lamarck), Echinometra viridis Agassiz, Diadema antillarum Philippi, Lytechinus variegatus (Lamarck), Tripneustes ventricosus (Lamarck)]. Therefore arrangement of pores affects strength of rigid thecae. Sutures are stronger than plates in most species examined, but cracks cross sutures, and tests of E. tribuloides frequently break along sutures. It is not yet proven that sutures increase toughness of rigid tests by relieving stress on plates or stopping cracks. If resisting failure under impact is important, then preconditions for acquiring rigidity are life in a low energy habitat or accessory structures which absorb or spread impacts.
The green sea urchin Strongylocentrotus droebachiensis is highly selective in its choice of algal foods. In the rocky subtidal zone in Newfoundland, urchins are usually very abundant and preferred algae, the more r-selected species (with higher growth and fecundity rates) are largely restricted to a refuge in shallow water where wave action impedes urchin grazing. The width of this subtidal refuge is greatest in exposed locations and small or nil in moderately exposed to protected areas. In winter, it extends to more protected locations and to greater depths in exposed locations. This extension is favoured by the urchin's low winter consumption rates, the limitation of urchin grazing by frequent heavy wave conditions, and probably by accelerated algal growth rate (Alaria, Laminaria). The fringe is subsequently reduced by urchin grazing during spring and summer. The main algae in the deeper urchin-dominated zone are the non-preferred, K-selected species, which escape urchin grazing due to their unpalatibility or to their grazing resistant (calcareous) structure. The fitness of urchins in overgrazed barrens is very low, their rates of growth and gamete production being almost nil. Urchins moving up to graze in shallow water have increased fitness but encounter greater energetic costs and greater risks of mortality. Urchin recruitment is infrequent and their numerous adaptations for surviving through periods of food shortage may permit them to produce offspring at a later time when food becomes available. -from Author
This chapter focuses on the photosensitivity of echinoids. Echinoids show their photosensitivity in a variety of responses: morphological and physiological color change, in the responses of particular effectors such as spines and podia, and possibly in reproductive activity. The photosensitivity of echinoids is characterized by the simplicity of the receptive apparatus and the relative complexity of the associated nerve supply. It is agreed that the reactions of whole urchins are profoundly influenced by their physiological state, a complex and intangible factor that involves sensory adaptation. Psammechinus miliaris overturns when suddenly illuminated on the oral side. This was categorized as a dorsal light reaction. Urchin shows both morphological and physiological color changes and both are influenced by light. Several kinds of pigment are involved for the above phenomenon, including hydroxynaphthaquinone, melanin, chromolipoid, and an iron-containing pigment of nuclear origin. The spines of echinoids generally respond to mechanical and chemical stimuli, but a few respond also to photic stimuli. It describes the diurnal rhythm of activity in several echinoids.
The purple sea urchin Strongylocentrotus purpuratus (Stimpson) has been shown to exhibit phenotypic variation that is dependent on habitat. The interaction of two common conditions existing in the intertidal zone; viz., food limitation and wave action resulting in spine damage, were explored under laboratory conditions. Changes in overall size, test weight, and jaw length were determined as urchins were subjected to different food levels and spine damage. Results indicate that food availability influences overall growth to a greater degree than does spine damage. An increase in the length of the jaws begins almost immediately following a reduction in the amount of food. Animals that were subjected to spine damage, in addition to repairing spines, appeared to allocate a greater amount of material to the lanterns and tests, which suggests that spine repair may stimulate overall calcification. Reinforcement of the test clearly has survival value for sea urchins of exposed rocky shores.
Intertidal and subtidal Strongylocentrotus droebachiensis (Muller) often hide among rocks or cover themselves with debris, including macroalgae, mussel shells, and pebbles. Similar reactions in other species of sea urchins have been interpreted as a response to bright sunlight. This study examined the response of S. droebachiensis specifically to ultraviolet radiation (UVR). In laboratory studies using artificial irradiation, S. droebachiensis exposed to UVR (290 to 400 nm) and photosynthetically active radiation (PAR, 400 to 700 nm) sought shade and covered themselves significantly more frequently than those exposed only to PAR. In outdoor aquaria, individuals were exposed to ambient solar radiation that was filtered to create 4 treatments (dark, PAR, PAR + UVA, or PAR + WA + UVB) and observed for 6 h as total solar irradiance changed with time of day. Sea urchins covered themselves with significantly more material when exposed to PAR + UVA + UVB than in all other treatments, and in response to total irradiance. The amount of covering by sea urchins exposed to PAR + UVA (320 to 400 nm) varied over the course of the day, but were typically less than those exposed to UVB (295 to 320 nm). These sea urchins covered themselves more than those exposed to PAR alone or held in the dark. Sea urchins exposed to PAR alone did not differ in the amount of covering from those held in the dark, regardless of time of day. The amount of covering correlated significantly with WE and UVA irradiance independently, but not PAR irradiance. This study does not rule out that multiple cues may cause the covering response, but it demonstrates that S. droebachiensis seeks shelter and covers itself in response to UVR, primarily UVB wavelengths or a combination of WA and WE, presumably to avoid W-induced damage.
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At temperatures of 10–12°C the sea urchin Strongylocentrotus droebachiensis (O.F. Müller),on 80% of the occasions tested, moved away from water that had passed over lobsters or crabs. At lower temperatures an increasing proportion of urchins remained inactive, but of those that were active, 80% still moved away from the scent of predators. At 10–12°C a similar proportion moved towards water that has passed over Laminaria, but at reduced temperatures a smaller proportion of the active urchins responded in this way. The attractant in Laminaria is an unstable, volatile hydrophobic compound with a low molecular weight.
A relationship between macroalgae (Phyllophora antarctica and Iridaea cordata), the sea urchin Sterechinus neumayeri, and the sea anemone Isotealia antarctica in Antarctica is described. Both macroalgal species are chemically defended against herbivory by S. neumayeri. Where macroalgae and urchins co-occur in the field, over 95% of the urchins use macroalgae as cover and the vast majority of available drift is held by them. Urchins collected from sites without macroalgae prefer macroalgae over other cover materials in the laboratory, suggesting that they make an active behavioral choice to cover with macroalgae when available. Macroalgal cover acts as a defense against the major sea urchin predator, I. antarctica. Algal cover significantly increases the likelihood that urchins will escape from I. antarctica because the anemones' tentacles attach to the algae, which are subsequently released by the anemone or by both the urchin and the anemone. This defense is physical as thalli from which defensive chemicals have been extracted are equally protective. Macroalgae appear to derive benefit from this relationship because fertile drift plants are retained in the photic zone where they can continue to contribute to the gene pool. The urchins also extend the effective horizontal and vertical distributions of the macroalgae, which may help sustain the range of these algal populations in periods of reduced light availability. Hence, even though the macroalgae are chemically defended from urchin herbivory, this relationship is apparently mutualistic. It benefits the sea urchins by providing a defense against their primary predator and benefits the macroalgae by helping to sustain a reproductive population.
1. Lytechinus variegatus (Lamarck) covers the parts of its skin that are exposed to light with fragments taken from its surroundings.
2. The covering is taken up by the tube feet, assisted by the spines, and held in place by the tube feet acting in relays. It may be orientated with respect to the light source. There are indications of adaptability of behaviour where the covering pieces offer resistance to being lifted.
3. Covering is related to light and to diurnal light changes, being assumed in strong light and rejected, after a varying interval of time, in darkness. Both continuous bright light and decreases in light intensity evoke covering. The tube feet react to the same stimuli and the speed of their extension is roughly proportional to the change of intensity.
4. The tendency to cover is increased after a sojourn in darkness and is greater in pale individuals than in dark ones.
5. Urchins can be photosensitized by injection of dyes so that they cover in dim light.
6. The prehension and holding of covering does not involve the oral and aboral nerve rings.
7. The relation of covering to light and environment favours the idea that it acts as a screen against strong light.
A population of the purple sea urchin Strongylocentrotus purpuratus Stimpson was studied at Sunset Bay, Oregon. Three sub-populations had different size-frequency distributions. Such differences in size resulted from differences in growth rate and ultimate size. Two environmental components were examined as possibly causing the different rates of growth: a component of @'weather@' which broke spines, and food availability and consumption. These two components are important in determining growth rate and ultimate size of these animals.
We measured the movement and orientation of sea urchins at 2 sites in each of 4 habitats on urchin barrens in the northern Gulf of St. Lawrence, eastern Canada. We tagged the urchins measuring 25 to 70 mm in test diameter using a non-invasive technique involving a knot of fine monofilament thread tied around one spine. Smaller urchins (<25 mm) were tagged by tightening a loop around the test. Daily displacement increased markedly going from large juveniles (measuring 10-15 mm in diameter) to small adults (15-20 mm) and from small adults to large adults (>25-70 mm); however, no effect of size was detectable among large adults measuring from 25 to 70 mm. The increased movement with size was associated with a change in foraging, as gut analysis revealed a marked increase in the proportion of brown algae with increasing size. For large adults, the maximum net distance displaced per day varied among sites from 1.0 to 4.9 m d-1, and mean displacement varied from 0.40 (SE = 0.07) to 1.72 (SE = 0.28) m d-1. Distance moved also varied with habitat, and was greater in habitats that were further from kelp beds. Orientation was random and individuals showed frequent reverses in direction from day to day. Hunger state did not affect displacement, as there was no difference in distance moved between starved and fed urchins which were released in the barrens. However, urchins transplanted from kelp beds to the barrens were less active than urchins removed from and returned to the barrens. The shifts in movement with size are probably important in determining the size structure of urchins at different depths. The great distance covered by larger urchins as they move over open surfaces in search of favourable resources probably leads to their increased numbers in shallow habitats where food is abundant.
Echinus esculentus, the larger common sea-urchin, occurs in the British Isles between tide-marks on rocky shores at about low-water spring-tide level in the localities given in Table I, page 292. It is, however, absent from apparently suitable foreshores in the Plymouth district, for reasons which are discussed in the present paper. Chadwick (1) states that “In Port Erin Bay it may be collected by hand on the beach, and on the ruined breakwater at low water of spring tides.” Elmhirst (2) records that “In this district (Millport) E. esculentus occurs abundantly between tide-marks in spring and early summer on rocky coasts; a few may be found at almost any other season. About February or early March a shoreward migration seems to set in, so that in suitable weather conditions some hundreds may be collected at springs between April and June. Then their abundance decreases until about November,from when until January it is at a minimum.”
The nymphs of the West African assassin bugs Paredocla and Acanthaspis spp. disguise themselves with a cover of dust, sand and soil particles (‘dust coat’) and additionally pile a ‘backpack’ of larger objects, such as empty prey corpses and plant parts, on their abdomen. We investigated the effect of this conspicuous camouflage in interactions of the bugs with ants, their main prey, as well as in encounters with their own predators. Experiments with three ant species showed that the dust coat impedes chemical and tactile recognition of the nymphs by ant workers and thus may serve to increase their hunting success. The backpack appeared to play only a minor role in this context. In arena experiments with three potential predators (spiders, geckos and centipedes), camouflaged nymphs were significantly more likely to survive than denuded bugs. Here the observed effect was mainly attributable to the backpack, which enhanced the concealing effect of the dust coat and confused visually orienting predators. In addition, in the case of an attack, it could be shed to distract the enemy while the bug escaped, thus functioning in a similar manner as a lizard’s tail.
The role of anti-herbivore organismal defenses in algae–herbivore interaction is frequently investigated without taking into account the potential role of environmental factors in mediating the interaction. Here we reexamine the interaction between the highly acidic, brown alga Desmarestia viridis and the green sea urchin, Strongylocentrotus droebachiensis, by incorporating a previously overlooked facet, the effect of changes in the wave environment on the ability of the urchin to establish contact with the alga. Factorial experiments in a wave tank (presence versus absence of waves; real versus mimic algae) showed that the aggregation of urchins on D. viridis was more than 2-fold greater in the absence than in the presence of waves. Similar numbers of urchins made contact with natural and mimic D. viridis plants, both with and without waves, indicating that any external release of chemicals (acid) from the alga had no perceptible repulsive effect on the urchin. The ability of the urchins to climb onto D. viridis increased markedly when urchin density attained a critical level. These results were consistent with field observations that urchins readily attack D. viridis under conditions of low wave action but do not under conditions of moderate wave action. We conclude (1) that the chemical makeup of D. viridis alone is neither necessary nor sufficient to limit contacts by the urchins and that (2) wave action is a major factor explaining the survival of D. viridis on urchin barrens, because waves limit the movements of the urchins towards the alga. We recommend that studies addressing marine algal defenses against herbivores be more comprehensive and examine interactions between algal traits, the physical environment, and the abundance and behavioral repertoire of herbivores.
Echinoids, notably Lytechinus variegatus and Tripneustes ventricosus, and other reef flat animals (brachyuran crabs, chitons and ophiuroids) were observed to suffer heavy mortality in Puerto Rico during extreme, midday low water stands which occur in the spring and summer seasons. Death often resulted from prolonged exposure to intense heating (up to 40C) in pools and slowly circulating bodies of water over periods of clear and calm weather; desiccation caused death in echinoids which subsequently floated away from the reef with the rising tide. The tolerance limits to exsiccation and high thermal stress were determined and found to lie within the lethal range realized on the reef. Unprotected Tripneustes may also be killed from exposure to the shorter radiations of sunlight. Severe mortalities were observed in populations of Lytechinus (64%) and Tripneustes (86%) located at a shallow depth toward the lee side of the reef. Less affected were the echinoids Echinometra lucunter, Diadema antillarum and Brissus unicolor. Similar, tide-related echinoid kills are expected to occur at other localities in the Caribbean region.
Natural and manipulative experiments were used to evaluate the effect of algal cover on sea urchin (Strongylocentrotus polyacanthus) distribution on submarine pinnacles at Shemya Island in the western Aleutian Archipelago. In July, pinnacle tops had dense kelp stands with low densities of sea urchins. In subsequent months, urchin densities increased as annual algal cover declined. In the summer, removal of specific combinations of macroalgae from the pinnacle tops resulted in an increase in urchin density. Artificial structures that imitated certain common seaweeds were placed on pinnacle tops and inhibited urchin movement. Clod cards that were used to measure relative abrasion rates on vegetated and cleared pinnacles demonstrated that algae cause a significant amount of abrasion. This study showed that the physical structure of the dominant annual alga, Desmarestia viridis, is capable of limiting sea urchin distribution, movement, and grazing. In this study, a potential food source actively controlled herbivore distribution and was the primary cause for the persistence of isolated kelp communities surrounded by barrens dominated by sea urchin grazing.
Field observations of covering (placement of objects on upper surface) and migration (movement between upper and lower rock surfaces) by the sea urchin, Paracentrotus lividus (Echinodermata: Echinoidea), were conducted at Lough Hyne, Ireland. Numerous hypotheses have been proposed to explain such behaviour in echinoids but have failed to consider the importance of multiple abiotic and biotic factors. Our study aimed to quantify the influence of interacting variables upon both behaviours in P. lividus using log-linear analysis. Our resultant model ranked the factors influential in covering behaviour as follows: (1) availability of covering item; (2) migratory behaviour; (3) size of P. lividus; (4) time of day; (5) time of year; and (6) predation intensity. The same variables were ranked differently in terms of their importance to the migratory behaviour of P. lividus. Moreover, the model showed, for the first time, an unequivocal relationship between covering and migration . Covering was mostly restricted to upper-rock-surface individuals, and therefore daylight periods, and was most intense in summer. This supports the theory that echinoids may cover to avoid over-exposure to light. We also conclude that rock upper surfaces are important as the principal source of food; lower surfaces may provide refuges from predators, with migration between these surfaces as a result. Certain individuals become too large to fit in boulder interstices and therefore incapable of migration to lower surfaces, whereas small individuals rarely migrate to upper surfaces. Models such as these provide a baseline for understanding the relative importance and interrelationship of factors of complex behaviour.
Interspecific relationships and trophic function within the urchin guild are considered in light of experiments and observations performed in situ. Two conclusions are reached: 1) interactions between members of the guild contribute to its persistence, and 2) the plant-herbivore interactions so important in structuring this community can best be evaluated when guild members are treated as a unit. As with other mixed species trophic units, the mechanisms of interspecies facilitation operate to reduce the effects of predation and increase foraging efficiency.
The green sea urchin, Strongylocentrotus
droebachiensis, exhibited immediate behavioural responses to waterborne chemosensory cues from two durophagous predators, the Atlantic wolffish, Anarhichas
lupus, and the edible crab, Cancer
pagurus; as well as from crushed conspecifics and crushed blue mussels, Mytilus
edulis. The response patterns were dose dependent and diet dependent. Strong responses were elicited by water conditioned by echinivorous wolffish (97.5%), undiluted urchin extract (73%), undiluted mussel extract (52.5%), and by water conditioned by echinivorous crab (45%). In contrast, urchin extract diluted to 1%, mussel extract diluted to 10%, and water conditioned by predators on a mussel diet elicited weak responses (~20%). Infection by the endoparasitic nematode Echinomermella
matsi had no significant effect on the response pattern of S. droebachiensis. There was no conclusive evidence of an alarm response to the predators per se, as the weak response to stimuli from non-echinivorous wolffish and crab, as well as from the seastar Asterias
rubens, may have been caused by chemical cues transmitted from their mussel diet. The diet-dependent response to predators suggests that active predators were labelled by chemical cues from their echinoid prey. The chemical cue from echinivorous wolffish acted as both an arrestant and as a repellent, whereas the response to other cues was predominantly or exclusively repellent. The response to echinivorous wolffish was quantitatively stronger than, and qualitatively different from, the response to other stimuli, including undiluted urchin extract. The wolffish is apparently being labelled by a latent chemical cue which derives its potency from activation by, or interaction with, substances in the digestive system of the wolffish. We interpret this novel phenomenon as evidence of alarm signal magnification. The induced behavioural modifications demonstrate the green sea urchins' ability to detect chemical cues associated with active durophagous predators, and would therefore seem to have adaptive potential as a predator defence mechanism.
One strategy for predator avoidance involves the creation of a structural refuge. Onuphid polychaetes characteristically ornament above-sediment portions of their tubes (=tube-caps) with shell and algal debris. These species feed on the sediment surface through an opening in the tube-cap, and thus the ability to detect a surface predator while feeding would be advantageous. An investigation of the function of the ornamentation in Diopatra spp. suggests that ornamentation facilitates predator detection and avoidance. Three intensities of mechanical disturbance were applied directly to D. ornata tube-caps. When ornamented tube-caps were stimulated, the response of worms to the three intensities were significantly different, and increased in duration with greater intensities. In contrast, when no ornamentation was present, the responses were not significantly different, and were similar to the low-intensity response when ornamentation was present. This suggests that ornamentation should allow a worm to distinguish between harmful (high intensity due to mobile epifaunal predators) and profitable (low intensity due to drift algae) disturbances, and furthermore, worms with ornamented tube-caps should be more successful in escaping surface predators. Densities of intertidal populations of D. cuprea at Tom's Cove, Virginia, USA, correlated with the amount of tube ornamentation, consistent with this predator detection and avoidance hypothesis. Final tube-cap lengths of laboratory D. ornata and field D. cuprea were inversely related to the size of attached debris. When large debris was attached, cap formation ceased earlier and caps were shorter than when small debris or no debris was attached. Cryptic and food-catching functions would predict that highly ornamented tubes would be most advantageous, while only a few large debris would be required for disturbance transmission. Laboratory specimens showed no selectivity between 0.5 or 1.5 cm2 shell; or 1.0 cm2 or 3 to 8 cm2 algae, and utilized shell and algae when available and according to relative abundance. Tube-caps of field specimens also showed positive correlations between shell attached and shell abundance in the local sediment. While such lack of selectivity may enhance cryptic properties of the tube-cap, it is argued that conditions seldom exist which would permit selectivity of debris size or of specific material. These data are consistent with the hypothesis that ornamentation functions as a created refuge for predator detection and avoidance and further suggest that the availability of ornamental debris in the environment indirectly can affect these species' distributions and abundances.
The density, diet, movement, and covering behavior of Toxopneustes roseus (Agassiz) were investigated in rhodolith beds in the Gulf of California. Densities varied from a mean of 0.4 to 1.8/20 m2 with most urchins occurring in aggregations. Spatial patterns of urchins varied with depth, with greatest abundance at intermediate
depths (7.5–9.4 m) in the middle of the rhodolith bed. Urchins ate rhodoliths and nongeniculate coralline algal crusts almost
exclusively, despite the availability of other algae. The mean amounts ingested were 3.87 and 7.96 g carbonate/individual
per day. Even when food was abundant, animals were highly mobile, moving an average of 6.6–11.7 cm/h depending on site and
time of day. Diel movement may be a behavioral adaptation to avoid surge, which is greatest during the day. Covering behavior
may also be related to surge, as the ratio of covering material:body weight and the percent cover of material held were highest
at the site with the most surge. While an urchin consumed rhodoliths, its movement spread the grazing impact over large areas.
Bioturbation resulting from urchin feeding, movement, and covering activity probably benefits the rhodoliths by turning them,
which maintains rhodolith integrity, prevents fouling, and contributes to bed persistence.
Field sampling and laboratory experiments examined whether ultraviolet radiation (UVR) affects the reproduction or the accumulation
of mycosporine-like amino acids (MAAs) and ascorbic acid in ovaries of the green sea urchin Strongylocentrotus droebachiensis (Müller). Ovaries of sea urchins sampled across a depth gradient (0.5–10 m) in March 1998 did not differ in their gonadal
index, or in concentrations of MAAs, or ascorbic acid. Concentrations of MAAs and ascorbic acid in ovaries were higher in
sea urchins collected from a kelp bed compared with those collected from a community of crustose coralline algae. The concentrations
of MAAs in ovaries varied seasonally, peaking in March, when sea urchins had high gonadal indices just before spawning. Ovaries
of sea urchins maintained on controlled diets from October 1997 to April 1998 accumulated significantly higher concentrations
of MAAs when fed a diet rich in MAAs than did ovaries of sea urchins fed an alga lacking MAAs, but the gonadal indices did
not differ between diets. Sea urchins accumulated principally one MAA, shinorine, but not others that were available in high
concentrations in their diet. Neither the gonadal index nor the ovarian concentrations of MAAs were affected by daily exposure
of adult urchins to UVR for 6 months. Concentrations of ascorbic acid in ovaries did not differ among diets or UV-treatments.
The percentages of nutritive phagocytes and gametic cells were not affected by diet or UVR, and did not co-vary with concentrations
of MAAs or ascorbic acid in ovaries. These data support previous demonstrations that female sea urchins accumulate MAAs from
their diet of macroalgae, but further show that the accumulation is selective for specific MAAs, particularly shinorine, and
that adult S. droebachiensis do not accumulate MAAs in their ovaries or eggs in response to UV-exposure. These are also the first experimental studies
to address whether MAAs are affected by or regulate gametogenesis, and indicate that they do not.
At Discovery Bay, Jamaica, Tripneustes ventricosus lives in beds of the turtle grass Thalassia testudinum. Especially during daylight hours, it covers its aboral surface with fragments of this plant and other objects. Normally pigmented, wild-type sea urchins covered themselves significantly less with Thalassia when sunlight was experimentally decreased to 66% or 32% ambient intensity. Consistent with this result, naturally occurring sea urchins exhibited significantly less covering at a deep (3.5m) site than at a shallow (1m) site, where light intensities at the bottom were 619 and 946mol s–1 m–2, respectively. The graded covering response to light intensity suggests that covering is a defense against damaging solar radiation. Albino sea urchins covered themselves significantly more with Thalassia than wild-type sea urchins in both full and 66% sunlight. In addition, at the shallow site where they accounted for about 4% of the population, they showed significantly greater covering than wild-type urchins. The greater covering response of albino sea urchins suggests a greater susceptibility to solar radiation.
"Covering" or "heaping" behaviour is common to a number of regular echinoids living in a variety of different habitats. Many theories have been proposed to explain this behaviour, among which are several that link covering to light, including ultraviolet (UV) light. However, previous investigations of this light theory have been largely qualitative. In the present study, we used a systematic laboratory protocol to examine quantitatively the covering behaviour of the shallow water echinoid, Paracentrotus
lividus, under four different light regimes: white light (400–700 nm), UV-A+B (315–400 nm), UV-A (320–400 nm), and darkness. These experiments demonstrated that light, in particular UV light, influences the covering behaviour of P.
lividus. Under the UV regimes, significantly more individuals were found to display covering behaviour, and individuals spent more time at the base of aquaria, farthest from the light source. Moreover, covering items were retained for the longest period of time under the UV-A+B regime. We propose that protection against the harmful effects of UV radiation may be one of the functions of covering behaviour in P.
lividus.
The faecal shield of cassidine larvae is generally thought to have evolved as a defence against predators, but field evidence for this is only anecdotal. We investigated the effectiveness of the shield as defence against natural enemies and as protection from ultraviolet (UV‐B) radiation in the shield beetle Cassida rubiginosa Müller (Coleoptera, Chrysomelidae). We also investigated if the construction and bearing of the shield is associated with fitness costs for the larvae in the absence of natural enemies.
Using continuous video surveillance of individual prey, we determined the predator complex of the larvae in the field. Against the main predator, the paper wasp Polistes dominulus Christ (Hymenoptera, Vespidae), the faecal shield was not effective at all. Only few other generalist predators attacked the larvae and thus represented no major mortality factor. By contrast, the faecal shield was highly effective against parasitoids, an unexpected trait described here for the first time.
In dual‐choice bioassays we found no attractive effect of the faecal shield on the endoparasitoid Foersterella reptans (Hymenoptera, Tetracampidae), but a removed faecal shield facilitated oviposition.
There was no protective effect of the faecal shield against UV‐B radiation in a laboratory experiment. However, irradiated larvae suffered from a higher mortality rate and reached a lower pupal weight, independent of whether or not they carried a shield.
We found no measurable fitness costs for the larvae associated with bearing the faecal shield. Advantages (protection from desiccation, wind) seem to outweigh the costs, even in the absence of enemies.
Although many studies on the defensive function of Cassidine shields have been published, this is to our knowledge the first to consider the actual predation pressure in natural situations. This step is rarely undertaken in studies on proposed defensive traits. However, verification that a proposed selection pressure is in fact present in the field is crucial for demonstrating the value and function of any trait.
Oscillating-flow-tank experiments were conducted to evaluate the effect of wave-induced oscillatory flow on feeding by subtidal sea urchins Strongylocentrotus nudus (A. Agassiz). Feeding rates by two size groups (mean test diameter=53 and 80 mm) were measured for rehydrated dried blades and fresh live thalli of kelp Laminaria spp. Feeding rate of the larger sea urchins was markedly reduced at the peak velocity of 0.3 m/s and virtually ceased beyond ≈0.40 m/s. The peak velocities at which feeding rate began to decrease and reached almost nil were somewhat lower for the smaller sea urchins than for the larger ones. The velocity limit for feeding does not appear to be a function of temperature. Movement by sea urchins was reduced to half the rate in still water at the peak velocity of 0.30–0.40 m/s. Sea urchins could hardly move beyond 0.70 m/s. The depth variation in the mean of the wave-induced significant peak bottom water velocity, predicted from 6-yr offshore wave data available on the northeastern Pacific coast of Honshu, Japan, was consistent with depth distributions of S. nudus and kelp. The predicted frequency of the significant peak velocity <0.40 m/s, in which sea urchin grazing might be possible, was as high as 70% at 12 m depth but was only 3% at 2 m depth. Mirroring this, sea urchins were almost absent at 2 m depth and increased in density with increasing depth while the kelp decreased in density with increasing depth and were almost absent at 12 m depth.
The predatory impact of the American lobster Homarus americanus and the Atlantic wolffish Anarhichas lupus on the green sea urchin Strongylocentrotus droebachiensis was investigated in a multifactorial experiment. Both predators exhibited either Type 2 or Type 3 functional responses to increasing prey density, but the magnitude of the response differed for the two predators, and for different prey sizes. Predation on large (>20 mm) sea urchins increased approximately three-fold, i.e., from 1.12 to 3.54 urchins·day−1 for wolffish, and from 0.35 to 0.97 urchins·day−1 for lobster, when prey density was increased sixfold, i.e., from 5 to 30 urchins·tank−1. Although more urchins were killed at the highest density, the proportion of available urchins that were killed dropped by ≈50%. Predation on small (⪯20m) sea urchins was similar for both predators, increasing from ≈0.5 to ≈1.9 urchins·day−1 with increased prey density. In the lobster treatment, a rock crab, Cancer irroratus Say, was included as alternative prey. The lobsters killed 5.78% of the total number of available rock crabs, and 5.01% of the total number of available urchins, but lobster predation on urchins was nearly halved in replicates where the crab was killed. Experimental factors other than prey density and prey size, i.e., season; availability of food and physical refuges for the prey, and whether the prey had been fed or starved prior to the experiment , had no significant effects on the predation rates of either predator. These results are consistent with the hypothesis that green sea urchin outbreaks may be triggered by reductions in predation pressure. There was no evidence of significantly increased predation on morbid sea urchins although ≈1% of the experimental sea urchin population exhibited symptoms of amoeboid, Paramoeba invadens (Jones), disease.
The symbiotic associates of hermit crabs (excluding parasites and flora) are reviewed worldwide. The review includes species found on the shells occupied by hermit crabs (epibiotic species), species boring into these shells (endolithic species), species living within the lumen of the shell (either free-living or attached to the shell), species attached to the hermit crabs themselves, and hypersymbionts. In total over 550 invertebrates, from 16 phyla are found associated with over 180 species of hermit crabs. Among these associates, 114 appear to be obligate commensals of hermit crabs, 215 are facultative commensals, and 232 are incidental associates. The taxa exhibiting the highest number of associates are arthropods (126), polychaetes (105), and cnidarians (100). The communities of species associated with Dardanus arrosor, Paguristes eremita, Pagurus bernhardus, Pagurus cuanensis, and Pagurus longicarpus are the best studied and harbor the most diverse assemblages of species. While trends in biodiversity of hermit crab assemblages do not follow predicted patterns (e.g., hermit crabs within the Indo-West Pacific do not harbor more species than those from temperate regions), this is suggested to reflect a lack of sampling rather than a true representation of the number of associates. Hermit crabs date to at least the Cretaceous and provided a niche for a number of groups (e.g., hydractinians, bryozoans, polydorids), which were already associates of living gastropods. Apparently hermit crab shells initially supplied a substrate for settlement and then these symbiotic relationships were reinforced by enhanced feeding of symbionts through the activity of the hosts. Through their use and recycling of gastropods shells, hermit crabs are important allogenic ecosystem engineers in marine habitats from the intertidal to the deep sea. Hermit crabs benefit from some symbionts, particularly cnidarians and bryozoans, through extension of shell apertures (alleviating need to switch into new shells) and by providing protection from predators. However, hermit crabs are also negatively impacted (e.g., decreased reproductive success, increased predation) by some symbionts and a review of egg predators is provided. Thus, the symbiotic relationships between hermit crabs and many associates are difficult to characterize and often exhibit temporal changes depending on environmental and biological factors. Research on the biology of these symbionts and the costs/benefits of their associations with hermit crabs are analyzed. While some associates (e.g., Hydractinia spp.) have been studied in considerable detail, for most associations little is known in terms of the impacts of symbionts on hosts, and future experimental studies on the multitude of relationships are suggested.
We dived at regular intervals (8-, 12- or 24-h) over periods up to 24 days to quantify the feeding activities of identified sea stars along permanent transects in the upper sediment bottom zone (8–11 m deep). In this habitat, large individuals of four sea stars predominated. The diet of Asterias vulgaris (molluscs and echinoderms) was intermediate between that of Leptasterias polaris (mainly molluscs) and that of Crossaster papposus (mainly echinoderms), whereas the diet of Solaster endeca strongly differed from the other sea stars, as it only fed on holothuroids. Calculation of the Ivlev electivity index indicated little or no selection for many abundant prey species, whereas some rare prey in this zone (e.g., Mytilus edulis) were strongly selected. We quantified prey size selection, and observed evidence of selection on smaller individuals when feeding on infaunal bivalves (possibly the deeper burying of larger individuals limited attacks) and selection of larger individuals when feeding on epifaunal prey (possibly to maximize energetic intake). We observed A. vulgaris feeding on Mya truncata, which had been captured by L. polaris (kleptoparasitism) and this bivalve disappeared from the diet of A. vulgaris in areas where we experimentally removed L. polaris. Estimations of foraging rates over 100 days relative to prey availability indicated strong interactions among the sea stars themselves. C. papposus likely have a strong impact on conspecifics, L. polaris and A. vulgaris, and A. vulgaris on L. polaris. In contrast, <1% of total biomass of the most abundant prey of L. polaris (M. truncata) and C. papposus (Strongylocentrotus droebachiensis) was consumed in 100 days.
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Animal decorations are normally interpreted as signals of quality. In spiders, however, decorations may have different functions, including the attraction of prey to the web or making the spider cryptic to predators. To date, there is scant evidence for the latter hypothesis. Here we use the burrow-decorating wolf spider Lycosa tarantula to test whether turrets around the burrow serve to prevent burrow invasion and predation from the Occitan scorpion Buthus occitanus . We located spiders and scorpions in field enclosures and manipulated the presence or absence of decorations or turrets. We found that the presence of the turret decreases the rate of burrow invasion and improves spider survival, possibly because the turret makes the burrow cryptic to scorpions. In addition, a field survey showed that burrows with larger decorations had a lower chance of being invaded by scorpions. These results provide evidence that the decoration has an antipredatory function in nature.
Field and laboratory observations suggest that the covering response of Evechinus chloroticus is not significantly related to light avoidance. A positive response of the podia to contact stimuli elicits covering .which may be important for the capture of food, particularly algal debris.
Individuals of Strongylocentrotus purpuratus (Stimpson) are found covered with a variety of debris. Algae and surf grass often are cover on the aboral surface and are eaten on the oral surface. Strongylocentrotus purpuratus individuals show no tendency to drop their cover at night and assume it again at daybreak. Individuals of this species are more extensively covered in areas of surge activity than they are in tidepools. The materials most frequently used for cover also differ in these two areas. The availability of drift materials is the most important factor in determining the extent of covering and the types of covering materials held by Strongylocentrotus purpuratus.
Burrow decorations as antipredatory devices Behavioral Ecology, 17, 586e590. ARTICLE IN PRESS ANIMAL BEHAVIOUR, --, - 8 Please cite this article in press as: Cle ´ ment P. Dumont et al., Multiple factors explain the covering behaviour in the green sea urchin, Strongylocentrotus droeba-chiensis
- J L Williams
- Moya
- J Larano
- D H Wise
Williams, J. L., Moya-Larano, J. & Wise, D. H. 2006. Burrow decorations as antipredatory devices. Behavioral Ecology, 17, 586e590. ARTICLE IN PRESS ANIMAL BEHAVIOUR, --, - 8 Please cite this article in press as: Cle ´ ment P. Dumont et al., Multiple factors explain the covering behaviour in the green sea urchin, Strongylocentrotus droeba-chiensis, Anim. Behav. (2007), doi:10.1016/j.anbehav.2006.11.008
Daily movement of the sea urchin Strongylocentrotus droebachiensis in different subtidal habitats in eastern Canada. Marine Ecology Prog-ress Series, 317, 87e99. Ebert, T. A. 1968. Growth rates of the sea urchin Strongylocentrotus purpuratus related to food availability and spine abrasion
- C P Dumont
- J H Himmelman
- M P Russell
Dumont, C. P., Himmelman, J. H. & Russell, M. P. 2006. Daily movement of the sea urchin Strongylocentrotus droebachiensis in different subtidal habitats in eastern Canada. Marine Ecology Prog-ress Series, 317, 87e99. Ebert, T. A. 1968. Growth rates of the sea urchin Strongylocentrotus purpuratus related to food availability and spine abrasion. Ecology, 49, 1075e1091.