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Specialist herbivores reduce their susceptibility to predation by feeding on the chemically defended seaweed Avrainvillea longicaulis
Limnology and Oceanography
Abstract
The tropical green seaweed Avrainvillea longicaulis is a low preference food for coral-reef fishes, and it produces a brominated diphenylmethane derivative called avrainvilleol that significantly deters feeding by reef fishes in field bioassays. In contrast to the pattern for fishes, the ascoglossan gastropod Costasiella ocellifera and the crab Thersandrus compressus live on and eat only Avrain- villea. The gastropod sequesters avrainvilleol from its algal host and uses this compound as an effective defense against predatory fish. The crab does not sequester chemical defenses; however, it is camouflaged when on AvrainviNea and thus also experiences less predation when associated with this alga. Specialization on this chemically defended seaweed allows Costasiella to deter and Thersandrus to avoid predation. When coupled with other recent studies of specialist marine herbivores, these findings suggest that predator avoidance and deterrence are major advantages associated with the evolution of feeding specialization among herbivorous marine invertebrates.
... The Caribbean Costasiella ocellifera (C. lilianae) contains avrainvilleol (112), a brominated diphenylmethane dietary algal derivative, from feeding on the algae Avrainvillea longicaulis [316,325]. Avrainvilleol (112) possesses deterrent properties against the tropical damselfish Pomatocentrus coeruleus at 100 ppm [316,325]. ...
... lilianae) contains avrainvilleol (112), a brominated diphenylmethane dietary algal derivative, from feeding on the algae Avrainvillea longicaulis [316,325]. Avrainvilleol (112) possesses deterrent properties against the tropical damselfish Pomatocentrus coeruleus at 100 ppm [316,325]. ...
... M. germaineae retains active chloroplasts form its algal diet, the calcareous green alga Cymopolia barbata, from which it also accumulates prenylated bromohydroquinones, such as cyclocymopol (115) [330]. Cyclocymopol (115) is similar to the deterrent avrainvilleol (112) mentioned above [325]. Caliphylla mediterranea, instead, seems to rely only on a defensive cryptic behavior to avoid predators, lacking propionates or other defensive chemistry [331]. ...
The natural products of heterobranch molluscs display a huge variability both in structure and in their bioactivity. Despite the considerable lack of information, it can be observed from the recent literature that this group of animals possesses an astonishing arsenal of molecules from different origins that provide the molluscs with potent chemicals that are ecologically and pharmacologically relevant. In this review, we analyze the bioactivity of more than 450 compounds from ca. 400 species of heterobranch molluscs that are useful for the snails to protect themselves in different ways and/or that may be useful to us because of their pharmacological activities. Their ecological activities include predator avoidance, toxicity, antimicrobials, antifouling, trail-following and alarm pheromones, sunscreens and UV protection, tissue regeneration, and others. The most studied ecological activity is predation avoidance, followed by toxicity. Their pharmacological activities consist of cytotoxicity and antitumoral activity; antibiotic, antiparasitic, antiviral, and anti-inflammatory activity; and activity against neurodegenerative diseases and others. The most studied pharmacological activities are cytotoxicity and anticancer activities, followed by antibiotic activity. Overall, it can be observed that heterobranch molluscs are extremely interesting in regard to the study of marine natural products in terms of both chemical ecology and biotechnology studies, providing many leads for further detailed research in these fields in the near future.
... As a general rule, most marine herbivores eat a wide variety ofalgae, and most marine plants lack host-specific herbivores Hay and Steinberg, in press). The few specialized plant-herbivore relationships that have been documented involve chemically well-defended plants and small relatively sedentary herbivores (see also Hay et al., , 1989Hay et al., , 1990aHay et al., , 1990b. It is generally believed that specialized plantherbivore associations, like other associations between large marine hosts and small guests, are evolutionarily favored because small guests are effectively protected by their hosts from many would-be predators (Vermeij, 1983;Vermeij et al., 1987;Hay et al., 1989Hay et al., , 1990aHay et al., , 1990bHay and Steinberg, in press). ...
... The few specialized plant-herbivore relationships that have been documented involve chemically well-defended plants and small relatively sedentary herbivores (see also Hay et al., , 1989Hay et al., , 1990aHay et al., , 1990b. It is generally believed that specialized plantherbivore associations, like other associations between large marine hosts and small guests, are evolutionarily favored because small guests are effectively protected by their hosts from many would-be predators (Vermeij, 1983;Vermeij et al., 1987;Hay et al., 1989Hay et al., , 1990aHay et al., , 1990bHay and Steinberg, in press). When and where these associations arose, however, are questions that have rarely been discussed in the literature on plant-animal interactions. ...
... Previous studies have suggested that the algae most likely to harbor host-specific herbivores are chemically well-defended. Predators and generalized grazers that act as potential agents of mortality for algal-associated guests are deterred by the chemistry of the host alga (see Hay et al., , 1989Hay et al., , 1990aHay et al., , 1990bHay and Steinberg, in press). This hypothesis was developed mainly for tropical plantherbivore associations, but it is also plausible for temperate Atlantic fucoids and their guests. ...
A survey of cool-temperate North Pacific and North Atlantic marine plants and herbivorous molluscs and their descendants was undertaken to determine the time of origin and the biogeographical history of specialized host-guest relationships between plants and herbivores. Of 12 such associations, 6 (50%) were established no earlier than the Pliocene. These six associations resulted from the invasion of either the plant (three cases) or the herbivore (three cases) from geographical regions other than the one in which the association was forged. These results are contrary to the widely held view that specialized ("coevolved") relationships tend to be ancient, and highlight the importance of biotic interchange as a biogeographical process influencing the opportunity for trophic specialization.
... Each aquarium was equipped with its own filtered seawater source and air emitter and represented a replicate in one of the following treatments: psammophytic algae (aquarium with sterile sand and one plant each of Avrainvillea sp., Caulerpa sertularioides (S.G.Gmelin) M.Howe, and Halimeda sp.; n=9), or epilithic algae (aquarium with sterile sand and a rock with Halimeda sp. and diminutive bryopsidalean algal growth present; n=9), epilithic algae control (aquarium with sterile sand and an aquarium rock; n=1), or psammophytic algae control (aquarium with sterile sand only; n=1). Psammophytic algal taxa were selected based on their high abundance at the collection site, as well as their documentation as kleptoplast sources for Plakobranchus or other sacoglossan sea slugs (Hay et al. 1990, Maeda et al. 2012, Christa et al. 2013, 2014c. Live rock for the epilithic algae treatment was collected from Hunakai Beach, O'ahu three weeks prior to the trial and was cultured in the large tank housing the aquaria to allow the diminutive green algae to increase in biomass. ...
... P. ocellatus' preference for diminutive bryopsidalean green algae was further illustrated in the sequestration preference trials. When only large bryopsidalean genera, known to be kleptoplast sources for sacoglossans (Hay et al. 1990, Christa et al. 2013, 2014c, were offered, P. ocellatus did not sequester any new plastids. Additionally, slugs offered both large and diminutive taxa replenished their kleptoplasts, and molecular analyses of these kleptoplasts indicated that only chloroplasts from diminutive taxa were sequestered. ...
... Some evidence suggests that preference may be due, in part, to incentives offered by algae, such as predator-deterring secondary compounds (Jensen 1997). As an example, the sacoglossan Costasiella ocellifera Simroth sequesters both chloroplasts and the predator deterrent avrainvilleol from its algal host, and, as a result, is able to deter predators (Hay et al. 1990). To date, no studies have assessed secondary chemistry of diminutive bryopsidalean algae, but they may also be offering similar anti-predatory compounds. ...
The sacoglossan sea slug species complex Plakobranchus ocellatus is a common algivore throughout the tropical Pacific, including the Hawaiian Islands. Plakobranchus ocellatus is kleptoplastic - it sequesters and retains algal chloroplasts - a characteristic that can be exploited to molecularly characterize diminutive bryopsidalean algae that are typically difficult to locate, collect, and identify. Previous DNA barcode analyses of both P. ocellatus and its kleptoplasts have been conducted primarily in the western Pacific and have only minimally sampled the most eastern populations in the Hawaiian Islands. Using two chloroplast markers rbcL and tufA, kleptoplast samples from an O'ahu population of P. ocellatus were amplified and cloned to identify their algal sources. Plakobranchus ocellatus sequester chloroplasts from up to 11 bryopsidalean algal species, all but one being diminutive in thallus size. Notably, eight of the detected algal species were new records to the Hawaiian Islands. A sequestration preference study demonstrated that the O'ahu population of P. ocellatus preferentially sequesters chloroplasts from diminutive, epilithic taxa. Using coxI barcoding of P. ocellatus we showed the O'ahu population to be part of a clade that includes sequences from the neighboring island Maui, Australia, and the Philippines. The use of P. ocellatus as a novel sampling tool allows the exploration of the green algal community diversity and composition at a fine scale. This article is protected by copyright. All rights reserved.
... (4) Past work on interactions of marine predators and specialist herbivores focuses on tropical to warm-temperate species (e.g. Lewin 1970, Jensen 1984, Paul & Van Alstyne 1988, Hay et a1 1989, 1990b, Pennings 1990, Roussis et al. 1990) with little comparable work on their cold-water counterparts. ...
... Finally, sequestration and d e novo synthesis of defensive compounds have been demonstrated in several species of tropical ascoglossans (Paul & Van Alstyne 1988, Hay et al. 1989, 1990b, Roussis et al. 1990). The extent to which these 2 types of chemical defense vary latitudinally in carnivores, herbivores, and sessile prey is not well known (but see Bakus 1974, Bakus & Green 1974, McClintock et al. 1991 for discussion of geographic patterns). ...
... Association with and sequestration of secondary metabolites from algal hosts are predator avoidance and deterrence mechanisms of many tropical ascoglossans (Paul & Van Alstyne 1988. Hay et al. 1989, 1990b. De novo synthesis of defensive compounds occurs in tropical and perhaps temperate species (Roussis et al. 1990, this study). ...
Four common species of temperate NE Pacific ascoglossan (= sacoglossan) sea slugs were examined in 1990 and 1991 to determine the nature and effectiveness of their defensive responses and the potential ecological importance of predation. The 3 small, cryptic species (Placida dendritica, StiLiger fuscovittatus, Alderia modesta) responded to mechanical stimulation by waving and auto-tomizing cerata (finger-like projections on dorsal surfaces), secreting viscous white fluid, and reducing body surface pH. These responses, however, were ineffective deterrents against common intertidal predatory fishes and crabs: the predators readily consumed the cryptic herbivores in short-term laboratory experiments. Furthermore, predators s~gnificantly reduced densities of A. modesta on algal mats of Vauchena sp. in a 12 d field experiment conducted in Yaquina Bay, Oregon, USA. Thus, small, cryptic ascoglossans were subject to intense predation pressure In contrast, the large, conspicuous Aplysiopsis enterornolphae had more intense defensive responses (e.g. ejection of viscous fluid, acidic secretions), and few predators consumed the ascoglossan.
... Several studies have been conducted investigating the species-specific defensive capacity in sacoglossans [54][55][56]. In all these cases however, the deterrent capabilities of sea slugs were tested largely on fish and a few non-cnidarian invertebrates. ...
... In seven instances of kleptoparasitic behaviour by the wrasse, ingested prey were observed to be rejected shortly after capture, with the prey item falling on top of another mushroom coral and being readily ingested. This agrees with the observations of Hay and coworkers [55,68] regarding palatability and ingestion behaviour of Costasiella ocellifera and T. lunare. It can therefore be suggested that one of the mechanisms by which predatory mushroom corals capture most benthic prey is by the temporary elevation of rejected prey and the opportunistic capture of prey. ...
Recent studies revealed that reef corals can eat large-sized pelagic and benthic animals in addition to small planktonic prey. As follow-up, we document natural ingestion of sea slugs by corals and investigate the role of sacoglossan sea slugs as possible prey items of scleractinian corals. Feeding trials were carried out using six sacoglossan species as prey, two each from the genera Costasiella, Elysia and Plakobranchus, and four free-living solitary corals (Danafungia scruposa, Fungia fungites, Pleuractis paumotensis and Heteropsammia cochlea) as predators. Trials were carried out under both in-situ and ex-situ conditions with the aim to observe ingestion and assess signs of prey consumption based on tissue loss of prey individuals over time. Significant differences were observed in both ingestion time and consumption state of prey between prey species, with three of them being ingested more rapidly and preferentially consumed over the others. Additionally, prey size was found to be a significant factor with larger prey (>12 mm) being ingested more slowly and rarely than smaller ones (<6 mm and 6–12 mm). Comparisons of consumption capability among predators showed no significant difference with all coral species showing similar preferences for prey species. While no specific mechanism of prey capture is proposed, we also document instances of kleptoparisitism and resuspension of prey items by wrasses. This study highlights the important distinction between opportunistic prey capture and true predation events.
... The ability to change colour derived from algal pigments shows a negative relationship with the amount of decoration in species of Pugettia (Hultgren & Stachowitz, 2008). Other majoids more permanently mimic both the colour and the morphology of a particular host alga, presumably leading to a near-obligate specialization (Wicksten, 1983;Griffin & Tranter, 1986;Hay et al., 1990;Goh et al., 1999;Tazioli et al., 2007;Hultgren & Stachowicz, 2011). Species of Huenia (Epialtidae) permanently mimic the shape and colour of the coralline algae (green or brown) on which they live ( fig. ...
... Thersandrus compressus matches colour of the environmental green algae that contain compounds that deter grazing fishes. According to Hay et al. (1990), it feeds exclusively on the alga but does not sequester the algal compounds; it is protected from predation by its felt-like texture, flattened legs and protective coloration. If separated from the noxious algae, Thersandrus compressus is quickly eaten or loses appendages to predatory fishes. ...
... and Durvillaea spp.), which is a unique adaptation for true limpets and allows this species to remain submerged while avoiding predation and competition usually associated with low to mid tidal levels. Like other specialist herbivores, acquisition of resistance to host chemical defences may have facilitated a shift in ecological niche in S. scurra (Hay et al. 1990;Ritter et al. 2017). Additionally, S. viridula has a propensity to move both at individual scales to avoid heat (Broitman et al. 2018) and at population scales via a hypothesized range expansion southwards as ocean surface temperature increases (Broitman et al. 2018). ...
Comparative genomic studies of closely related taxa are important for our understanding of the causes of divergence on a changing Earth. This being said, the genomic resources available for marine intertidal molluscs are limited and currently, there are few publicly available high‐quality annotated genomes for intertidal species and for molluscs in general. Here we report transcriptome assemblies for six species of Patellogastropoda and genome assemblies and annotations for three of these species ( Scurria scurra , Scurria viridula and Scurria zebrina ). Comparative analysis using these genomic resources suggest that and recently diverging lineages (10–20 Mya) have experienced similar amounts of contractions and expansions but across different gene families. Furthermore, differences among recently diverged species are reflected in variation in the amount of coding and noncoding material in genomes, such as amount of repetitive elements and lengths of transcripts and introns and exons. Additionally, functional ontologies of species‐specific and duplicated genes together with demographic inference support the finding that recent divergence among members of the genus Scurria aligns with their unique ecological characteristics. Overall, the resources presented here will be valuable for future studies of adaptation in molluscs and in intertidal habitats as a whole.
... The mounds alter the benthos through increased sedimentation, which modifies hard substrate to resemble soft sediment habitats (Foster et al., 2019;Littler et al., 2004). The alga's ability to engineer habitat structure, its complex branching and holdfast morphology (Littler & Littler, 1992;Olsen-Stojkovich, 1985), and its possible herbivore-deterring secondary metabolites (see Hay et al., 1990) have all influenced the surrounding ecosystem by contributing to significant shifts in surrounding invertebrate (Foster et al., 2019;Longenecker et al., 2011), algal (Peyton, 2009;Smith et al., 2002), and fish communities (Langston & Spalding, 2017). ...
The relative rates of sexual versus asexual reproduction influence the partitioning of genetic diversity within and among populations. During range expansions, asexual reproduction often facilitates colonization and establishment. The arrival of the green alga Avrainvillea lacerata has caused shifts in habitat structure and community assemblages since its discovery in 1981 offshore of Oʻahu, Hawai‘i. Field observations suggest this species is spreading via vegetative reproduction. To characterize the reproductive system of A. lacerata in Hawai‘i, we developed seven microsatellite loci and genotyped 321 blades collected between 2018 and 2023 from three intertidal sites at Maunalua Bay and ʻEwa Beach. We observed one to four alleles at multiple loci, suggesting A. lacerata is tetraploid. Each site was characterized by high genotypic richness ( R > 0.8). However, clonal rates were also high, suggesting the vegetative spread of A. lacerata plays a significant role. The importance of clonal reproduction for the persistence of A. lacerata in Hawai‘i is consistent with the ecological data collected for this species and observations of other abundant macroalgal invaders in Hawai‘i and other regions of the world. These data demonstrate the necessity for implementing appropriate population genetic methods and provide insights into the biology of this alga that will contribute to future studies on effective management strategies incorporating its reproductive system. This study represents one of the few that investigate green algal population genetic patterns and contributes to our understanding of algal reproductive system evolution.
... and Durvillaea spp.), which is a unique adaptation for true limpets and allows this species to remain submerged while avoiding predation and competition usually associated with low to mid tidal levels. Like other specialist herbivores, acquisition of resistance to host chemical defences may have facilitated a shift in ecological niche in S. scurra (Hay et al. 1990;Ritter et al. 2017). Additionally, S. viridula has a propensity to move both at individual scales to avoid heat (Broitman et al. 2018) and at population scales via a hypothesized range expansion southwards as ocean surface temperature increases (Broitman et al. 2018). ...
... Studies of specialist consumers, especially herbivores that specialize on chemically defended algae or cyanobacteria, are revealing much about how natural products can influence trophic interactions. Saccoglossans, a group of opisthobranch mollusks, often specialize on green algae, and they can sequester algal secondary metabolites, which are then used for their own defense against predators (Paul and Van Alstyne, 1988;hay et al., 1990;Becerro et al., 2001). By stealing defensive compounds from their food sources, these soft-bodied slugs avoid the costs of making chemical defenses. ...
... g. Cluster #6: Avrainvillea longicaulis (Major descriptors: "evolution," "resistance," "chemical defenses") -Investigates the seaweed species Avrainvillea longicaulis' chemical defenses and antioxidant activity, with Hay et al. [78] and Zubia et al. [79], examining its ability to produce secondary metabolites deterring herbivory. h. ...
Seaweed research has gained substantial momentum in recent years, attracting the attention of researchers, academic institutions, industries, policymakers, and philanthropists to explore its potential applications and benefits. Despite the growing body of literature, there is a paucity of comprehensive scientometric analyses, highlighting the need for an in-depth investigation. In this study, we utilized CiteSpace to examine the global seaweed research landscape through the Web of Science Core Collection database, assessing publication trends, collaboration patterns, network structures, and co-citation analyses across 48,278 original works published since 1975. Our results demonstrate a diverse and active research community, with a multitude of authors and journals contributing to the advancement of seaweed science. Thematic co-citation cluster analysis identified three primary research areas: "Coral reef," "Solar radiation," and "Mycosporine-like amino acid," emphasizing the multidisciplinary nature of seaweed research. The increasing prominence of "Chemical composition" and "Antioxidant" keywords indicates a burgeoning interest in characterizing the nutritional value and health-promoting properties of seaweed. Timeline co-citation analysis unveils that recent research priorities have emerged around the themes of coral reefs, ocean acidification, and antioxidants, underlining the evolving focus and interdisciplinary approach of the field. Moreover, our analysis highlights the potential of seaweed as a functional food product, poised to contribute significantly to addressing global food security 2 and sustainability challenges. This study underscores the importance of bibliometric analysis in elucidating the global seaweed research landscape and emphasizes the need for sustained knowledge exchange and collaboration to drive the field forward. By revealing key findings and emerging trends, our research offers valuable insights for academics and stakeholders, fostering a more profound understanding of seaweed's potential and informing future research endeavors in this promising domain.
... Marine algae are the renewable living resources which are rich source of structurally important novel and biologically active metabolites (Bhaskar and Kazuo 2005). Diverse secondary metabolites in many types of seaweed were reported as having defensive action against invertebrates in general (Hay et al. 1990) and insects in particular (Rizvi 2003;Biju et al. 2004;Rizvi and Shameel 2004). Usage of synthetic insecticides has more damaging effect on the environment and public health, so considering the above situation usage of most reliable toxic free and eco-friendly products has become a significant decision now a days in pest management (Oi et al. 2015). ...
Marine seaweeds enriched with natural bioactive compounds have been utilized in the current study to alleviate Aphis craccivora infestation in cowpea. Insecticidal and repellent activities were evaluated with extracts from four macroalgae (Padina pavonica, Sargassum tenerrimum, Portieria hornemannii and Gracilaria corticata) against A. craccivora adults. Samples were extracted using Soxhlet extraction with solvents of varying polarity (methanol, chloroform, acetone and hexane). In leaf dip bio-assay P. pavonica methanolic extract (PPME) and P. hornemannii chloroform extract (PHCE) showed highest mortality (> 85%) of A. craccivora (at 1.6%) concentration after 72 h of treatment, when compared with other 16 different seaweed extracts. In repellency test, the PPME and PHCE showed constant repellent effect at 1.6 per cent concentration with an IBT (Index of Behavioral Tendency) value (0.238, 0.213, 0.288, 0.188 and 0.275) and (0.250, 0.275, 0.275, 0.225 and 0.238) after 4, 8, 12, 18 and 24 h of treatment, respectively. GC–MS/MS analysis of PPME and PHCE revealed the most likely active constituents hexadecenoic acid methyl ester, phytol, and n-hexadecanoic acid as potential insecticidal compounds. Additionally, these two extracts were utilized to evaluate their synergistic effects with ginger and basil oils. The highest synergistic effect was observed in PHCE + basil + ginger oil (Synergistic ratio (SR), 1.44) followed by PPME + basil + ginger oil (SR, 1.41). The selected two seaweeds exhibited good synergistic effect with ginger and basil oil against cowpea bean aphid in laboratory condition. Hence, these seaweed extracts would be an alternative botanical pesticide in the development of IPM module for the management of cowpea aphids.
... Marine herbivores select their habitat based on their need for food and protection. Depending on the chosen environment, they are able to reduce their risk of being predated by other marine organisms [6]. Most marine herbivores have generalist feeding behaviors, however some develop host-specific preferences. ...
Due to climate change, the lagoon of Moorea in French Polynesia is impacted by cyanobacteria blooms asphyxiating corals, causing reef degradation and decreasing food resources. Lyngbya majuscula and Anabaena torulosa are two filamentous benthic cyanobacteria that proliferate on sand and corals. They produce many secondary metabolites that can be toxic. Anabaena torulosa produces cyclic lipopeptides such as laxaphycins A and B, composed of 11 and 12 amino acids, respectively. This cyanobacterium has been able to develop chemical strategies of protection against grazers, which can be repelled by the toxic molecules produced such as laxaphycin B. In turn, herbivores must circumvent these defenses and in some cases even take advantage of them to protect themselves from their own predators. This is the case of Stylocheilus striatus, a sea hare that feeds on Lyngbya majuscula and Anabaena torulosa, and appears to be less susceptible to predation on Anabaena torulosa. Stylocheilus striatus consumes the latter without being affected by laxaphycin B toxicity. To overcome this toxicity, the sea hare has developed an adaptive mechanism that allows the biotransformation of laxaphycin B into non-toxic acyclic laxaphycin B. While non-toxic laxaphycin A is bioaccumulated in its digestive gland, laxaphycin B undergoes two successive cleavages at the C-terminal position of two hydroxyleucines. In order to study the enzymatic mechanism involved in this biotransformation, we have synthesized various analogues of laxaphycin B. First, we optimized their chemical synthesis, allowing us to confirm the structure of trichormamide C, a natural peptide analogous to laxaphycin B. In a second step, the synthesized analogues could be submitted to the studied enzyme and showed the reproducibility of the cleavage on different sequences. First characteristics of the enzyme could be identified, such as its cleavage specificities. Finally, our efforts focused on the design of a minimal peptide sequence for the recognition of the enzyme, in order to consider different strategies to isolate it.
... These feeding preferences can be mediated by nutritive quality and secondary metabolites and by non-nutritional factors such as habitat choice (especially for mesograzers). It is, however, worth noting that evolution of feeding specialization through selection for food utilization ability or through selection for habitat are not mutually exclusive but rather act together: the associations of small mesograzers with their seaweed hosts may well be initially driven by predation avoidance but the association as such will then select for better host use ability (Hay et al. 1989(Hay et al. , 1990bDuffy and Hay 1991). Several kinds of evidence imply that secondary chemicals play a major role in feeding preferences. ...
... As a consequence, some plant species defended by metals have been reported to reduce levels of more expensive organic compounds (Davis et al., 2001;Tewes et al., 2018). In addition, specialist herbivores are often adapted to organic defensive compounds and even sequester them for their own defense against natural enemies (Hay et al., 1990;Strauss et al., 2002;Opitz and Müller, 2009). On the contrary, metals cannot be degraded metabolically so that they can hardly be detoxified by herbivores once they were ingested (Boyd, 2007). ...
... Photosynthetically produced compounds are utilized in the slug metabolism and, in some species, can sustain the slug without food (reviewed in Pierce and Curtis, 2012;Pierce et al., 2015). Most marine herbivores are generalists (Hay et al., 1990), but most sacoglossan species are oligophagous, feeding on a few species of closely related algae (Jensen, 1980;Klotchkova et al., 2010;Christa et al., 2014;Krug et al., 2016). Uncharacteristically, a few sacoglossan species, most notably Plakobranchus ocellatus (Maeda et al., 2012;Christa et al., 2013) and Elysia clarki (Curtis et al., , 2007Pierce et al., 2006;Middlebrooks et al., 2014), are able to feed on and sequester chloroplasts from a relatively large variety of green algal species; and then they utilize the array of plastids for photosynthesis for many months (Middlebrooks et al., 2014;Pierce et al., 2015). ...
Sacoglossan sea slugs feed by suctorially consuming siphonaceous green algae. Most sacoglossan species are feeding specialists, but the Caribbean coral reef-dwelling Elysia crispata is polyphagous and sequesters chloroplasts from multiple algal species into cells lining its digestive diver-ticulum for use in photosynthesis. We have used sequences of the chloroplast-encoded rbcL gene to compare the chloroplast donor algae in five populations of E. crispata from various Caribbean locations. We found that E. crispata utilizes more algal species than was previously known, including some algae previously not reported as present in the region. In addition, slugs from each location had unique chloroplast arrays with little overlap, except that all locations had slugs feeding on algae within the genus Bryopsis. This variation in diet between locations suggests that the slugs may be exhibiting local adaptation in their dietary choices, and it highlights ecological differences between the Caribbean-wide reef-dwelling ecotypes and the mangrove lagoon ecotypes found in the Florida Keys.
... Among the Limapontiidae, the Caribbean Costasiella ocellifera (C. lilianae), feeding on Avrainvillea longicaulis contains avrainvilleol (Figure 3.8), a brominated diphenylmethane dietary algal derivative, with deterrent properties against fish ( Hay et al. 1990). In the Mediterranean, Placida dendritica feeds upon both Bryopsis and Codium making use of the chloroplasts for camouflage. ...
Marine organisms produce a wide variety of molecules, often unique and critical for their survival in terms of feeding, reproduction, or protection. These natural products are at the basis of ecological specialization because they may affect species distribution, feeding patterns, community structure and biodiversity. However, a long way remains to be explored on how chemical ecology regulates marine ecosystems. “Opisthobranch” molluscs, comprising the commonly known sea slugs and sea hares, are no exception to this, and they present a wide variety of bioactive compounds protecting them against potential predators and competitors, and enhancing their ecological performance. Sea slug defenses include chemicals obtained directly from their prey, transformed dietary metabolites, or even de novo biosynthesized bioactive compounds. Over the last 30 years, many advances were achieved on chemical defensive strategies in sea slugs throughout different latitudes, from the tropics to the poles. In this chapter we describe what is known about the chemical ecology of marine slugs (“opisthobranchs”) from a biological perspective, and the molecules involved, focusing on the origins, bioactivities, and ecological roles in combination with other defensive strategies. Biogeographical and evolutionary aspects are also considered here. Often, chemical defenses are associated with warning (aposematic) colorations, allowing species to survive in exposed habitats, where predators learn to associate bright colorations with their bad taste. Many pigments, in fact, possess bioactive properties themselves (e.g. alkaloids), while being part of photosynthetic systems, or may act as sunscreens protecting from UV light. The biochemical pathways to build these natural products are usually complex and metabolically expensive, even when they come from the diet since the compounds have to be processed, transferred, or stored in specific sites. Chemical defense allocation is particularly common in sea slugs, with extensive literature reporting bioactive products stored in exposed, vulnerable areas, such as the mantle, foot, gills, and rhinophores; within mucus or ink secretions; in specialized glands, like mantle dermal formations (MDFs); and also occasionally in eggs, embryos, and larval stages. Overall, sea slugs offer a serendipitous world of chemical defensive strategies, in which all sort of mechanisms have appeared to favor their survival. Amazingly, the defensive strategies of marine slugs and the compounds used are not as variable in the distinct geographic areas, even if the kinds of predators, competitors, and threats may be remarkably different. Effective protection from potential enemies thus is achieved by similar patterns of chemical defensive strategies in very different ecosystems. The fascinating world of sea slugs still has a lot to offer and we should be able to deep into all the open aspects in the current frame of a changing environment.
... Only highly specialised herbivores Gorshkov (1976Gorshkov ( , 1978Gorshkov ( , 1980. belonging to Sacoglossan gastropods and decapods are capable of ingesting them (Hay et al., 1990). ...
The Indo-Pacific species Avrainvillea amadelpha (Montagne) A. Gepp & E.S. Gepp is reported for the first time from the Mediterranean Sea (Kerkennah Islands, Tunisia). The species is considered as introduced and invasive in the Hawaiian Archipelago. The Mediterranean specimens are studied and the reproductive structures are described and illustrated here for the first time. The possible origins and vectors of this introduction and the risk of propagation of the species in the Mediterranean Sea are discussed.
... In addition, the lack of herbivory may be due to the low digestibility of the algae; both Avrainvillea sp. and Halimeda sp. contain numerous compounds which may deter herbivory (Meyer et al., 1994;Hay et al., 1990;Paul & Alstyne, 1992). In addition, the partial calcification of H. kanaloana may serve as an added impediment to herbivory (Schupp & Paul, 1994). ...
The invasive macroalgal species Avrainvillea sp. and native species Halimeda kanaloana form expansive meadows that extend to depths of 80 m or more in the waters off of O‘ahu and Maui, respectively. Despite their wide depth distribution, comparatively little is known about the biota associated with these macroalgal species. Our primary goals were to provide baseline information on the fish fauna associated with these deep-water macroalgal meadows and to compare the abundance and diversity of fishes between the meadow interior and sandy perimeters. Because both species form structurally complex three-dimensional canopies, we hypothesized that they would support a greater abundance and diversity of fishes when compared to surrounding sandy areas. We surveyed the fish fauna associated with these meadows using visual surveys and collections made with clove-oil anesthetic. Using these techniques, we recorded a total of 49 species from 25 families for H. kanaloana meadows and surrounding sandy areas, and 28 species from 19 families for Avrainvillea sp. habitats. Percent endemism was 28.6% and 10.7%, respectively. Wrasses (Family Labridae) were the most speciose taxon in both habitats (11 and six species, respectively), followed by gobies for H. kanaloana (six species). The wrasse Oxycheilinus bimaculatus and cardinalfish Apogonichthys perdix were the most frequently-occurring species within the H. kanaloana and Avrainvillea canopies, respectively. Obligate herbivores and food-fish species were rare in both habitats. Surprisingly, the density and abundance of small epibenthic fishes were greater in open sand than in the meadow canopy. In addition, species richness was also higher in open sand for Avrainvillea sp. We hypothesize that the dense holdfasts and rhizoids present within the meadow canopy may impede benthic-dwelling or bioturbator species, which accounted for 86% and 57% of individuals collected in sand adjacent to H. kanaloana and Avrainvillea sp. habitats, respectively. Of the 65 unique species recorded in this study, 16 (25%) were detected in clove oil stations alone, illustrating the utility of clove-oil anesthetic in assessing the diversity and abundance of small-bodied epibenthic fishes.
... However, the occurrence of small-sized algae that commonly form filamentous turfs in Abrolhos, such as Sphacelariaceae and Ceramiaceae (Figueiredo 1997), may have been under-recorded. Many algae belonging to the richest families are well known for being herbivore-resistant, either by having deterrent secondary metabolites or by their tough calcified thalli (Hay and Duffy 1990;Hay and Fenical 1992;Hay et al.1994;Hay 1997;Paul 1997;Pitlick and Paul 1997). This suggests that fish, as the main herbivorous group on Abrolhos reefs, may influence the distribution patterns of macroalgae (Villaça and Pitombo 1997;Figueiredo 2000). ...
... However, the occurrence of small-sized algae that commonly form filamentous turfs in Abrolhos, such as Sphacelariaceae and Ceramiaceae (Figueiredo 1997), may have been under-recorded. Many algae belonging to the richest families are well known for being herbivore-resistant, either by having deterrent secondary metabolites or by their tough calcified thalli (Hay and Duffy 1990;Hay and Fenical 1992;Hay et al.1994;Hay 1997;Paul 1997;Pitlick and Paul 1997). This suggests that fish, as the main herbivorous group on Abrolhos reefs, may influence the distribution patterns of macroalgae (Villaça and Pitombo 1997;Figueiredo 2000). ...
Appendix 2 of A Rapid Marine Biodiversity Assessment of the Abrolhos Bank, Bahia, Brazil
Editors Guilherme F. Dutra, Gerald R. Allen, Timothy Werner, and Sheila A. McKenna
... Because few (if any) of the fishes in the northern habitats we studied perceive seaweeds as food, camouflage that allows the crab to blend into the background cover of benthic vegetation may be sufficient to reduce detection by predators. Seaweed chemical defenses can be effective against carnivores (e.g., Paul and Van Alstyne 1988;Hay et al. 1990aHay et al. , 1990b, but chemical protection from predation may confer little additional benefit in northern habitats if crabs camouflaged to match the algal background are rarely discovered. Thus, the specialist and generalist strategies may each be favored in different parts of Libinia's geographic range. ...
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.
... Plant defence and the effects of herbivores are strongly affected by patterns of selection on the herbivores themselves, especially by the risks herbivores face from predators. Selection for multiple plant toxins can be imposed by herbivores that sequester these compounds for their own protection or that seek refuge from enemies on noxious plants (Brower, 1958;Hay et al., 1989Hay et al., , 1990aCimino and Ghiselin, 1998). Chemical defences are the only form of protection that can be transferred from one trophic level to another. ...
Background:
Plants (attached photosynthesizing organisms) are eaten by a wide variety of herbivorous animals. Despite a vast literature on plant defence, contrasting patterns of antiherbivore adaptation among marine, freshwater and land plants have been little noticed, documented or understood.
Scope:
Here I show how the surrounding medium (water or air) affects not only the plants themselves, but also the sensory and locomotor capacities of herbivores and their predators, and I discuss patterns of defence and host specialization of plants and herbivores on land and in water. I analysed the literature on herbivory with special reference to mechanical defences and sensory cues emitted by plants. Spines, hairs, asymmetrically oriented features on plant surfaces, and visual and olfactory signals that confuse or repel herbivores are common in land plants but rare or absent in water-dwelling plants. Small terrestrial herbivores are more often host-specific than their aquatic counterparts. I propose that patterns of selection on terrestrial herbivores and plants differ from those on aquatic species. Land plants must often attract animal dispersers and pollinators that, like their herbivorous counterparts, require sophisticated locomotor and sensory abilities. Plants counter their attractiveness to animal helpers by evolving effective contact defences and long-distance cues that mislead or warn herbivores. The locomotor and sensory world of small aquatic herbivores is more limited. These characteristics result from the lower viscosity and density of air compared with water as well as from limitations on plant physiology and signal transmission in water. Evolutionary innovations have not eliminated the contrasts in the conditions of life between water and land.
Conclusion:
Plant defence can be understood fully when herbivores and their victims are considered in the broader context of other interactions among coexisting species and of the medium in which these interactions occur.
... However, the occurrence of small-sized algae that commonly form filamentous turfs in Abrolhos, such as Sphacelariaceae and Ceramiaceae (Figueiredo 1997), may have been under-recorded. Many algae belonging to the richest families are well known for being herbivore-resistant, either by having deterrent secondary metabolites or by their tough calcified thalli (Hay and Duffy 1990;Hay and Fenical 1992;Hay et al.1994;Hay 1997;Paul 1997;Pitlick and Paul 1997). This suggests that fish, as the main herbivorous group on Abrolhos reefs, may influence the distribution patterns of macroalgae (Villaça and Pitombo 1997;Figueiredo 2000). ...
... As some colour-changing species shift between discrete, different-coloured algal habitats, appropriate habitat selection appears to be crucial in mediating the effectiveness of colour camouflage Stachowicz, 2008a, 2010). In some cases, crabs more permanently mimic both the coloration and the morphology of a particular host plant in a form of masquerade, presumably leading to a near-obligate specialisation (Wicksten 1983;Griffin & Tranter 1986;Hay et al. 1990;Goh et al. 1999;Tazioli et al. 2007). As one spectacular example, the tropical Pacific crab Huenia heraldica has carapace projections and coloration that strongly resembles its host algae in the genus Halimeda (Wicksten, 1983) (Plate 1c). ...
Camouflage is one of the most common anti-predator strategies in the animal kingdom, and many examples of camouflage have become classic case studies of adaptation and natural selection (Cott 1940; Kettlewell 1955; Stevens & Merilaita 2009). Although most examples of animal camouflage involve body coloration or patterning, decorator crabs in the brachyuran superfamily Majoidea (majoids) are a large and diverse group of crabs best known for a distinctive form of ‘decoration’ camouflage, in which they attach materials from the environment to specialised hooked setae on their body. This unique form of camouflage is dependent both on crab morphology and behaviour, and makes decorator crabs an ideal group in which to study the adaptive consequences and mechanistic bases of camouflage. Decorator crabs are also fairly unusual among camouflaged animals in that the adaptive anti-predatory consequences of decoration camouflage have in many cases been directly tested in the field (Stachowicz & Hay 1999b; Thanh et al. 2003; Hultgren & Stachowicz 2008a). Yet despite its clear adaptive value, decoration camouflage varies widely across the majoids – both within and between species. Many majoids exhibit intra- and interspecific decreases in decoration with size (Dudgeon 1980; Wicksten 1993; Stachowicz & Hay 1999b; Berke & Woodin 2008; Hultgren & Stachowicz 2009). Along with experimental work documenting energetic costs of carrying decoration (Berke & Woodin 2008), and trade-offs with other forms of defence (Hultgren & Stachowicz 2008a), these data suggest that cost–benefit trade-offs may drive the evolution of decoration in these crabs (Hultgren & Stachowicz 2009). These results more broadly imply that the value of camouflage as a concealment strategy is strongly influenced by constraints such as body size, providing predictions to be tested in other groups of organisms.
... Phenolic compounds are secondary metabolites and thus not directly involved in algal primary processes such as photosynth- esis, cell division and reproduction. Phenolic compounds are characterized as stress compounds, it involves chemical protective mechanisms against biotic factors such as grazing [378,379], set- tlement of bacteria or other fouling organisms [380,381] and against abiotic stressors such as UV-radiation [382] and metal contamination [383,384]. However, some phenolic compounds, such as phlorotannins in brown seaweeds, also exhibit primary functions e.g. in growth and the development of the cell wall in Fucales [385]. ...
Due to diminishing petroleum reserves and deleterious environmental consequences of exhaust gases from fossil-based fuels, research on renewable and environment friendly fuels has received a lot of impetus in the recent years. However, the availability of the non-edible crops serve as the sources for biofuel production are limited and economically not feasible. Algae are a promising alternative source to the conventional feedstocks for the third generation biofuel production. There has been a considerable discussion in the recent years about the potential of microalgae for the production of biofuels, but there may be other more readily exploitable commercial opportunities for macroalgae and microalgae. This review, briefly describes the biofuels conversion technologies for both macroalgae and microalgae. The gasification process produces combustible gases such as H2, CH4, CO2 and ammonia, whereas, the product of pyrolysis is bio-oil. The fermentation product of algae is ethanol, that can be used as a direct fuel or as a gasohol. Hydrogen can be obtained from the photobiological process of algal biomass. In transesterification process, algae oil is converted into biodiesel, which is quite similar to those of conventional diesel and it can be blended with the petroleum diesel. This study, also reviewed the production of high value byproducts from macroalgae and microalgae and their commercial applications. Algae as a potential renewable resource is not only used for biofuels but also for human health, animal and aquatic nutrition, environmental applications such as CO2 mitigation, wastewater treatment, biofertilizer, high-value compounds, synthesis of pigments and stable isotope biochemicals. This review is mainly an attempt, to investigate the biorefinery concept applied on the algal technology, for the synthesis of novel bioproducts to improve the algal biofuels as even more diversified and economically competitive.
... The huge abundance of epiphytes raises the question of whether this alga has any defence mechanisms against epiphytes like other algae such as Gracilaria conferta (Weinberger et al. 1999), Chondrus crispus (Bouarab et al. 1999), and G. cornea (Friedlander et al. 2001). Phenolic compounds are involved in chemical protective mechanisms against grazing, (Hay et al. 1990;Coleman et al. 2007), settlement of other epiphytes (Lau and Qian 2000;Mokrini et al. 2008). The Gelidiales are reported to have a good amount of bromophenols (Whitfield et al. 1999) and G. acerosa is reported to contain terpenoids (Syad et al. 2012). ...
... A color-mediated crypsis strategy such as color change by sequestering diet-derived pigments has also been suggested as another camouflage strategy against predation in crabs (HAY et al., 1990;WOODS;MCLAY, 1996). Acanthonyx petiveri attached small algae to the rostrum (WILSON, 1987), but body color provided some crypsis regardless of coloration, and different color morphs of A. petiveri tended to associate selectively with algae of similar color. ...
Studies on the feeding preferences of marine herbivores are very important for our better understanding of the biology and the ecological role of these organisms. Members of the family Epialtidae are usually herbivores that mask themselves with pieces of seaweed and other materials to avoid predation. In order to better understand the mechanisms of food and decorating choices of the decorator crab Acanthonyx scutiformis, two multiple-choice feeding assays were performed using fresh seaweeds and artificial food containing crude extracts of the four seaweeds Osmundaria obtusiloba, Plocamium brasiliense, Sargassum sp., and Dictyota menstrualis, offered simultaneously to this crab species. In both assays the seaweed most consumed was O. obtusiloba, followed by P. brasiliense and Sargassum sp., while D. menstrualis was the least consumed. It is suggested that A. scutiformis is a generalist feeder, but with some preference for the perennial red seaweed O. obtusiloba and the chemically-defended seaweed P. brasiliense. Decorating behavior observations revealed the preferences of A. scutiformis by P. brasiliense. This decorating behavior can be interpreted as a mechanism to avoid generalist predators, since feeding and decorating preference were not associated and the crab used only small pieces of chemically defended algae.
... Qualitative defenses (toxins such as alkaloids and glucosinolates) act against generalist herbivores and are cheaper to produce, but specialist herbivores are often adapted to these defenses (Berryman 1988;Strauss et al. 2002). Specialist herbivores often use these compounds as a cue to locate their host plant, as an oviposition and feeding stimulant, and may sequester the qualitative plant defense compounds for their own defense (van der Meijden 1996;Hay et al. 1990;Müller et al. 2001;Bernays et al. 2003;Macel and Vrieling 2003;Nieminen et al. 2003). In the invasive area where specialist herbivores are absent, plant can shift their allocation to produce more of the cheap qualitative defenses against generalist herbivores without having the side effect of attracting the specialist herbivores. ...
According to the Shifting Defense Hypothesis, invasive plants should trade-off their costly quantitative defense to cheaper qualitative defense and growth due to the lack of natural specialist enemies and the presence of generalist enemies in the introduced areas. Several studies showed that plant genotypes from the invasive areas had a better qualitative defense than genotypes from the native area but only a few studies have focused on the quantitative defenses and tolerance ability. We compared structural defenses, tolerance and growth between invasive and native plant populations from different continents using the model plant Jacobaea vulgaris. We examined several microscopical structure traits, toughness, amount of cell wall proteins, growth and root-shoot ratio, which is a proxy for tolerance. The results show that invasive Jacobaea vulgaris have thinner leaves, lower leaf mass area, lower leaf cell wall protein contents and a lower root-shoot ratio than native genotypes. It indicates that invasive genotypes have poorer structural defense and tolerance to herbivory but potentially higher growth compared to native genotypes. These findings are in line with the Evolution of Increased Competitive Ability hypothesis and Shifting Defense Hypothesis. We also show that the invasiveness of this species in three geographically separated regions is consistently associated with the loss of parts of its quantitative defense and tolerance ability. The simultaneous change in quantitative defense and tolerance of the same magnitude and direction in the three invasive regions can be explained by parallel evolution. We argue that such parallel evolution might be attributed to the absence of natural enemies rather than adaptation to local abiotic factors, since climate conditions among these three regions were different. Understanding such evolutionary changes helps to understand why plant species become invasive and might be important for biological control.
... By residing within these macrophytes the small animals avoid accidental ingestion by larger herbivores that are deterred from feeding on the chemically defended host (Bernays & Graham 1988;Hay et al. 1989;Brawley 1992;Pennings & Paul 1992;Trowbridge 1992;Hay 1997). Secondly, some herbivores have become specially adapted to feed on chemically rich macrophytes and can even incorporate and sequester macrophytederived chemicals for use in their own defence (Brower 1984;Hay et al. 1987;Hay & Fenical 1988;Paul & Van Alstyne 1988b;Hay et al. 1990;Pennings 1990c). When extracted, the chemicals present in host macrophytes cause little reduction in feeding rate and even sometimes promote feeding, by their specialized herbivores (Hay et al. 1989;Nagle et al. 1998). ...
... The huge abundance of epiphytes raises the question of whether this alga has any defence mechanisms against epiphytes like other algae such as Gracilaria conferta (Weinberger et al. 1999), Chondrus crispus (Bouarab et al. 1999), and G. cornea (Friedlander et al. 2001). Phenolic compounds are involved in chemical protective mechanisms against grazing, (Hay et al. 1990;Coleman et al. 2007), settlement of other epiphytes (Lau and Qian 2000;Mokrini et al. 2008). The Gelidiales are reported to have a good amount of bromophenols (Whitfield et al. 1999) and G. acerosa is reported to contain terpenoids (Syad et al. 2012). ...
Seasonal variations in epiphytic assemblages on Gelidiella acerosa cultivated in 2different methods (Floating raft and Bottom concrete block) were studied for 13 months from November 2009 to November 2010 covering all 4 seasons (northeast monsoon, southwest monsoon, autumn and summer). Twenty-five macro algal species were found in raft culture. Chaetomorpha linum Jania adhaerens, Hypnea valentiae, and Lyngbya majuscula were the dominant epiphytes. Twenty-four epiphytic algae were recorded in bottom concrete block culture. Caulerpa racemosa, Caulerpa peltata, Struvea anastomosans, Zonaria variegata, Padina tetrastromatica, Dictyota sp., J. adhaerens, and L. majuscula were the dominant epiphytic species. Seasonal trend in total epiphytic density was the same in both the culture with maximum density during autumn season (192 ± 41 epiphytes m−2 in raft; 498 ± 10 epiphytes m-2 in concrete block) and minimum during northeast monsoon season (112 ± 5 epiphytes m−2 in raft; 247 ± 1 epiphytes m-2 in concrete block). Seasonal variations in dominant epiphyte density followed the trend of total epiphytes with highest in monsoon and autumn seasons. Salinity showed significant positive correlation with epiphyte density (r = 0.63, P = <0.05), while temperature showed strong negative correlation ( r = −0.63, P < 0.05; r = −0.77, P < 0.01). Light microscopic study and scanning electron microscopic study revealed the extent of penetration of epiphytes into host cortex cell. However, this should be confirmed with a transmission electron microscopic study. The results in this paper will be useful to the farmers in understanding the impact of epiphytes on crop yield and define the strategies to avoid epiphytes on G. acerosa in cultivation.
... Green macroalgae, mainly species of Bryopsidales are abundant and widely distributed in tropical seas, and known to produce mainly sesquiterpenoid and diterpenoid compounds (Blunt et al., 2009, and previous reviews of this author). Some of these metabolites have been implicated in well documented studies that evidenced its property as a chemical defense against grazing by several species of fishes (Hay et al., 1990;Wylie and Paul, 1988), and invertebrates such as gastropods (Davis et al., 2005), mollusk (Pennings and Paul, 1992), and sea urchins (Hay et al., 1994;Lima et al., 2008). ...
Species of Plocamium are known as prolific sources of halogenated secondary metabolites exhibiting few explored ecological roles. In this study the crude extracts from specimens of P. brasiliense collected in two distinct places, Enseada do Forno and Praia Rasa, Búzios, Estado do Rio de Janeiro, were evaluated as defense against the sea urchin Lytechinus variegatus and the crab Acanthonyx scutiformis. These specimens produce a similar amount of crude extract and also halogenated monoterpene compound-types, but individuals of P. brasiliense from Praia Rasa exhibit a major compound representing about 59% of the total chemicals. Natural concentrations of the crude extracts obtained from both specimens of P. brasiliense significantly inhibited the herbivory by the sea urchin L. variegatus, but had no significant effect on the feeding by A. scutiformis, a crab commonly associated to chemically defended host. Crude extract from P. brasiliense collected at Praia Rasa was more efficient as defense against L. variegatus than that crude extract from populations of this alga from Enseada do Forno, probably due to presence of a major secondary metabolite. These two studied population live under different environmental conditions, but they are only about 30 Km apart. However, it is impossible to affirm that environmental characteristics (abiotic or biotic) would be responsible for the difference of defensive potential found in the two populations of P. brasiliense studied here. Further genetic studies will be necessary to clarify this question and to explain why populations of a single species living in different but close locations can exhibit distinct chemicals.
Sacoglossan sea slugs have developed a variety of defence mechanisms against predation. Research on these mechanisms has focused primarily on the chemical defences of these slugs, and little information is available on nonchemical modes of defence, such as autotomy, a behaviour in which an organism voluntarily detaches body structures at a predetermined breakage point in response to danger or stress. Autotomy is diverse in sacoglossan sea slugs and has been well documented. Within Oxynidae, members can autotomize their tail and parapodial lobes, and slugs in Limapontiidae and Hermaeidae can detach their cerata. More recently, reports have been made of Elysia with the capacity to autotomize most of their body. However, despite the widespread assumption that autotomy in this group serves a defensive purpose, the effectiveness of the behaviour in ensuring survival against predation has seldom been examined. The objective of this study was to evaluate the role of autotomy in sacoglossans by assessing the effectiveness of ceratal autotomy in ensuring survival against the attacks of a generalist predator. Placida kingstoni is a small sacoglossan native to Florida and the Caribbean with the ability to autotomize its cerata. Individual P. kingstoni were exposed to shrimps of the Lysmata wurdemanni species complex for 10-min interactions. Most sea slugs were attacked by the predator, often more than once, but the majority of the slugs readily autotomized cerata and survived. Structure detachment was accompanied by the secretion of a mucus that facilitated the formation of ceratal clumps. Most of these clumps were consumed by the predator and effectively diverted their attention, allowing P. kingstoni to crawl away. In this species, the success of autotomy as a defensive strategy appears to be directly related to the palatability of autotomized cerata. The results of this study show that ceratal autotomy in P. kingstoni is an effective defence against predation. Autotomy is a behaviour with a high-energetic cost; however, it has convergently evolved within Heterobranchia on multiple occasions, and it is highly prevalent in cerata-bearing slugs. Although in sacoglossans much of this behaviour remains a mystery, this study provides a clear example of autotomy as a defensive mechanism.
Many small specialist herbivores utilize their food resources both for nutrition and as a structural refuge or resource. Trophic linkage cannot solely be inferred from physical association of herbivores with a potential food item, because herbivores may temporarily inhabit algae or plants on which they do not feed. Elysia papillosa, a small sacoglossan sea slug, consumes and sequesters chloroplasts from the siphonaceous, chlorophytic alga Penicillus capitatus; it also maintains moderate densities on this alga. Recently, E. papillosa was also infrequently found in association with the alga Penicillus lamourouxii, which displays density similar to that of P. capitatus. After collecting E. papillosa from each of the two algal species from a shallow-water site along the west central coast of Florida, we used DNA barcoding of the rbcL gene sequences in order to determine whether the slug was consuming both algal species. The molecular data indicated that E. papillosa consumed and sequestered chloroplasts from the same algal species from which they were collected. A laboratory feeding experiment tested whether algal diet (P. capitatus or P. lamourouxii) had an impact on slug growth rate as measured by change in body size (mm). After 3 weeks E. papillosa fed P. lamourouxii achieved a mean body length that was 1.5-2 times that recorded for slugs fed P. capitatus, but maximum growth depended on the original field host. Thus, while the highest densities of E. papillosa in the field occurred on P. capitatus, slugs grew much faster on P. lamourouxii in the laboratory. The observed association of E. papillosa with P. capitatus must be related to other factors, such as foraging efficiency, algal morphology, algal biochemistry, or algal suitability as a refuge.
From the green alga Avrainvillea amadelpha, two new naturally halo-benzaldehyde derivatives were isolated by various chromatographic methods along with 10 known metabolites of bromophenols, sulfonoglycolipid, and steroids. Based on the 1D and 2D NMR spectra as well as on MS data, the structures of the new compounds were identified as 5-bromo-2-(3-bromo-4-hydroxybenzyl)-3,4-dihydroxybenzaldehyde named avrainvilleal (1), and 3-iodo-4-hydroxy-benzaldehyde (2). Using SRB assay, both compounds showed mild and weak cytotoxic activity against HeLa and MCF-7 cancer cell lines, compared to the good activity of their extract (IC50 values 3.1 and 4.3 μg/mL, respectively). However, avrainvilleal (1) displayed an effective scavenged DPPH radical activity with IC50 value 3.5 μM, compared to the antioxidant quercetin with IC50 value 1.5 μM.
RESUMEN El género Avrainvillea Decaisne se considera un estabilizador de los fondos marinos, en áreas con sedimentos tanta orgánicos como carbonados. Por ser un contribuidor en biomasa, incapaz de ser consumido completamente por sus defensas químicas, su consumo está relegado a los mesoherbívoros, en su mayoría invertebrados. El presente estudio se realizó en la estación de muestreo Júcaro, ubicada en la bahía de Nuevitas. Como unidad de muestreo se empleó un marco de 20 cm de lado, y como muestra 30 montículos de Avrainvillea asarifolia Børgesen; las muestras se tomaron en agosto y diciembre de 2004, con previa remoción de las algas epífitas en mayo y septiembre. Se distinguen tres parámetros en el experimento: época (lluvia y seca), porción del talo (estipe, lámina) y manipulación (tratamiento y control). El análisis de los datos se realizó por vía paramétrica y no paramétrica. Se identificaron 8 Rhodophyta, 2 Ochrophyta y 4 Chlorophyta. El género Lejolisia y la especie L. exposita C. W. Schneider & Searles son nuevos registros para Cuba. Se determinaron 15 entidades de invertebrados, con predominio de los crustáceos peracáridos. Avrainvillea asarifolia es activamente consumida y la porción laminar es preferida a los estipes. Los mayores niveles de cobertura y diversidad de epífitas se presentaron en los estipes en ambas épocas, y las diferencias entre tratamiento y control no resultan evidentes. ABSTRACT The genus Avrainvillea Decaisne is regarded as a stabilizer of sea bottoms, whether in areas with organic deposits or carbonated deposits. Avrainvillea is a contributor of biomass that cannot be completely consumed by its chemical defence, and so its consumption is left for mesograzers, most of them invertebrates. This study was undertaken at the sampling station Júcaro located in the Bay of Nuevitas. The sampling frame was made up by a 20 cm. sided frame, and the sample consisted of 30 mounds of Avrainvillea asarifolia Børgesen. Samples were taken during August and December, 2004. There was a previous removal of epiphytes in May and September. There are three different parameters in the experiment: time (rainy season and dry season), thallus region (stipe and blade) and manipulation (treatment and control). Data analysis was parametrically and non parametrically made. Eight species of Rhodophyta, 2 Ochrophyta and 4 Chlorophyta were identified. The genus Lejolisia and the species L. exposita C. W. Schneider & Searles are new records for Cuba. Fifteen taxonomic groups of invertebrates were determined, being predominant peracarid crustaceans. Avrainvillea asarifolia is actively consumed, and blades are preferred to stipes. Most coverage levels and the highest diversity of epiphytes were observed in stipes during the rainy and the dry season. Differences between the treatments and the controls were not evident.
Background:
In the United States, one in six children are affected by neurodevelopmental disorders, and polybrominated diphenyl ethers (PBDEs) in flame-retardant chemicals are measured ubiquitously in children.
Objective:
We conducted a systematic a systematic review regarding developmental exposure to PBDEs and intelligence or Attention Deficit/Hyperactivity Disorder (ADHD) and attention-related behavioral conditions in humans.
Methods:
We searched articles published up to 26 September 2016, and included original studies that quantified exposures to PBDEs incurred any time in proximity to conception or during in utero, perinatal, or childhood time periods. We evaluated the risk of bias of individual studies and the overall quality and strength of the evidence according to the Navigation Guide systematic review methodology. We established criteria in advance to identify studies that could be combined using random effects meta-analyses (DerSimonian-Laird method).
Results:
Fifteen studies met the inclusion criteria; 10 studies met the criteria for intelligence and nine for attention-related problems. We rated studies generally with "low" to "probably low" risk of bias and rated the overall body of evidence as "moderate" quality with "sufficient" evidence for an association between Intelligence Quotient (IQ) and PBDEs. Our meta-analysis of four studies estimated a 10-fold increase (in other words, times 10) in PBDE exposure associated with a decrement of 3.70 IQ points (95% confidence interval: 0.83, 6.56). We concluded the body of evidence was of "moderate" quality for ADHD with "limited" evidence for an association with PBDEs, based on the heterogeneity of association estimates reported by a small number of studies and the fact that chance, bias, and confounding could not be ruled out with reasonable confidence.
Conclusion:
We concluded there was sufficient evidence supporting an association between developmental PBDE exposure and reduced IQ. Preventing developmental exposure to PBDEs could help prevent loss of human intelligence. https://doi.org/10.1289/EHP1632.
Covering: up to 2017
Chemical mediation regulates behavioral interactions between species and thus affects population structure, community organization and ecosystem function. Among marine taxa that have developed chemical mediation strategies, gastropods belong to a diverse group of molluscs found worldwide, including species with a coiled, reduced or absent shell. Most gastropods use natural products to mediate a wide range of behaviors such as defense, prey location or interactions with con- and hetero-geners. Their chemically defended diet, such as cyanobacteria, algae, sponges, bryozoans and tunicates, provides them with a considerable opportunity either as shelter from predators, or as a means to enhance their own chemical defense. In addition to improving their defenses, molluscs also use prey secondary metabolites in complex chemical communication including settlement induction, prey detection and feeding preferences. The assimilation of prey secondary metabolites further provides the opportunity for interactions with conspecifics via diet-derived chemical cues or signals. This review intends to provide an overview on the sequestration, detoxification, and biotransformation of diet-derived natural products, as well as the role of these compounds as chemical mediators in gastropod-prey interactions.
The general methods for extraction, purification, and identification of marine secondary metabolites are similar to, or involve slight modifications of, those used with terrestrial organisms. Marine methodologies for small organic molecules have been reviewed by Norris and Fenical (1985), and those for phlorotannins by Ragan and Glombitza (1986). Many compounds, such as those involved in prey detection, predator detection, and home site selection are less well understood chemically, and general reviews for methodologies dealing with the chemistry of these types of compounds are not available. With the exception of the phlorotannins, the large majority of known secondary metabolites from marine organisms are lipid soluble (Faulkner 1996, and earlier reviews cited therein). This produces significant experimental advantages because known quantities of lipid-soluble metabolites can be dissolved in volatile organic solvents such as diethyl ether and coated at desired concentrations onto surfaces (for tests as settlement cues or antifouling agents); onto palatable prey that have been blotted dry; or onto finely powdered, dried algal or animal tissue that can then be imbedded in a gel matrix (for tests as defenses against consumers see McConnell et al. 1982; Targett et al. 1986; Hay et al. 1987a, 1987b, 1994; Paul 1987, 1992; Henrikson & Pawlik 1995; Schmitt et al. 1995). After the solvent evaporates, these hydrophobic compounds adhere to the treatment surfaces or foods and do not dissolve when immersed in seawater while being used in settlement or feeding assays. Comparisons of feeding or settlement on treatments versus controls (treated with solvent only) allow for a determination of the effects of the compound alone. Modifications of these basic procedures have been applied widely in both field and laboratory investigations.
Seaweeds are one of the most important living resources of the ocean. Inspite of their wide applications in food and feed industries, they have gained importance as medicinal sources because of their high healing, antimicrobial and antioxidative properties. As a rich source of valuable chemical components, seaweeds are used in various other industries like cosmetics, Fuel, water treatment etc. Being a plant of unique structure and biochemical composition, seaweed could be used highly for its multi-functional properties in the form of food, energy, medicine and cosmetics. The distribution, properties and wide application of seaweeds are discussed in detail in this manuscript. INTRODUCTION Macroscopic marine algae, popularly known as seaweeds, form one of the important living resources of the ocean. Agar, carrageenan and alginate are popular examples of seaweeds these have been used as food for human beings, feed for animals, fertilizers for plants and source of various chemicals. In the recent past, seaweeds have also been gaining momentum as new experimental systems for biological research and integrated aquaculture systems. Seaweed products are used in our daily lives in one or the other way. For example, some seaweed polysaccharides are employed in the manufacture of toothpastes, soaps, shampoos, cosmetics, milk, ice creams, meat, processed food, air fresheners and a host of other items. In several oriental countries like Japan, China, Korea, etc., seaweeds are a staple part of the diet. Some typical examples of seaweed applications are narrated below.
Studies of red, Strongylocentrotus franciscanus, and purple sea urchins, Strongylocentrotus purpuratus, have yielded remarkable new discoveries that have advanced sea urchin ecology and biology in multiple fields. Sea urchins are model organisms for the study of developmental biology, as well as ocean warming, ocean acidification and climate change. Research results reveal that larval sea urchins in the plankton can reproduce asexually, change their larval morphology to enhance feeding, recover from months of starvation and disperse over the long distances, connecting populations of benthic adults. Adults living within interconnected metapopulations can utilize dissolved organics when algae are scarce, create rock pits and live for more than 100 years. Sea urchins are best known for their grazing impacts on algal communities. Overgrazing by sea urchins can reduce kelp forests to 'barrens' dominated by coralline algae, but more frequently they coexist in mosaics of algal and invertebrate patches. The spines of red sea urchins form a canopy that shelters juveniles and a suite of species, which, in conjunction with modulating algal resources, makes them ecosystem engineers. Recruitment is highly variable in space and time yet the drivers of recruitment success are poorly understood. Red sea urchins are the basis for important fisheries that lend themselves to spatial management strategies such as Marine Protected Areas. Sea urchins play such an important role in kelp forest communities that the successful management of the community and its ecosystem services will require an integrated ecosystem based approach incorporating what we know about sea urchin ecology.
Grazing is a major force structuring seaweed communities. Grazer–seaweed interactions are ecologically complex with important implications for seaweed standing biomass and community composition, the energy flow through the system, and higher trophic level predator–prey interactions. This chapter presents a summary of the vast amount of information on herbivore–seaweed interactions, focusing on key concepts illustrated with select examples. Grazer–seaweed interactions are first discussed from the grazer perspective, starting with several common classification systems of grazers based on their feeding mode, size, and diet specificity. This chapter then covers how grazers can impact seaweeds and seaweed communities in multiple ways, including mutualistic relationships between herbivores and seaweeds. Algal–herbivore interactions are then considered from the seaweed perspective, specifically types of algal defenses against grazing, such grazing tolerance and avoidance of herbivores, as well as structural and chemical defenses. The chapter ends with a brief consideration of potential climate change effects on grazer–seaweed interactions.
The identity of food sources and feeding preferences of specialist herbivores have been commonly inferred from spatial associations between consumer and food items. However, such basic information for well-known marine herbivores, sacoglossans (sea slugs), and their algal diets remains disappointingly lacking, especially from field studies. The sacoglossan, Elysia clarki (Pierce et al. in Molluscan Res 26:23–38, 2006), is kleptoplastic and sequesters chloroplasts from algal food to photosynthesize, so DNA identification of sequestered chloroplasts was employed to verify the algal species fed upon by the slug across its geographic range. The molecular information on the algae consumed by E. clarki was combined with field surveys of slugs and algae in slug habitats in the Florida Keys in July and August of 2008 in order to evaluate whether the diet of this herbivore could be predicted based on its spatial association with algae in the field. A considerable mismatch between food availability and kleptoplast identity was recorded. E. clarki commonly occupied areas devoid of potential food and often contained symbiotic plastids from algal species different from those most frequently found in the surveyed habitats. In three of the four study sites, algal species present were poor predictors of slug diet. These findings suggest that the photosynthetic capability of E. clarki may release the slug from the constraint of requiring proximity to its food sources and may allow for the potential lack of spatial coupling between this herbivore and its algal food. This combination of field surveys and DNA barcoding provided critical and previously unavailable information on herbivore feeding in this marine system.
Molecular and morphological evidence revealed the existence of two cryptic species of Costasiella Pruvot-Fol, 1951 in the Bahamas. A review of the literature indicates that one of these species is the western Atlantic widespread species Costasiella ocellifera (Simroth, 1895), whereas the other species is undescribed. The new species is externally similar to Costasiella ocellifera but can be distinguished by the absence of a penial stylet and the radular morphology. Phylogenetic and species delimitation analyses confirm that the new species is genetically distinct from C. ocellifera. The new species has only been found in the Bahamas, but there are possible records from Cuba and Jamaica.
Numerous small sedentary herbivores (mesograzers such as amphipods, small crabs, and gastropods) are resistant to seaweed secondary metabolites that deter larger, more mobile herbivorous fishes. In addition, specialist mesograzers experience reduced predation from fishes when living on seaweeds that produce these compounds. In this study we tested the hypothesis that generalist, as opposed to specialist, mesograzers can also benefit from reduced predation when they occupy chemically defended plants. Secondly, we assessed the hypothesis that low herbivore mobility, unconfounded by herbivore size or specialized feeding, selects for tolerance of seaweed chemical defenses, by comparing responses to the chemically defended brown seaweed Dictyota menstrualis of three sympatric, generalist amphipods that differ in mobility (Ampithoe longimana, Ampithoe valida, and Gammarus mucronatus). Response to Dictyota's chemical defenses varied as much among these three amphipods as among the phylogenetically distant fishes and mesograzers studied previously and supported the hypothesis that less mobile herbivores should be most tolerant of plant chemical defenses. In laboratory experiments, A. longimana moved little, preferentially consumed Dictyota over other seaweeds, and was unaffected by all Dictyota secondary metabolites tested. In contrast, G. mucronatus was active, it did not feed on Dictyota, and two of three Dictyota secondary metabolites deterred its grazing. Distribution of amphipods in the field suggested that these feeding patterns affected amphipod risk of predation. A. longimana reached its highest abundance on Dictyota, which is unpalatable to omnivorous fish predators, during the season when fish are most abundant. At the same time, the highly active G. mucronatus decreased to near extinction. Like G. mucronatus, A. valida was detterred by two Dictyota secondary metabolites, did not eat Dictyota, and disappeared when fishes were abundant. Experiments confirmed that A. longimana was less vulnerable to fish predation when occupying a chemically defended seaweed than when occupying a palatable seaweed. This decreased predation resulted primarily from a decreased frequency of encounter with predators when amphipods were on chemically defended plants. When we experimentally equalized encounter rates between omnivorous pinfish (Lagodon rhomboides) and the seaweed Dictyota menstrualis and Ulva curvata (unpalatable and palatable, respectively, to pinfish) in the laboratory, amphipods occupying these two plants were eaten at similar rates. In contrast, when live amphipods were affixed to Ulva and Dictyota and deployed in the field, amphipods survived only on Dictyota. Heavy fish grazing on Ulva in the latter experiment suggests that poor survival of amphipods on Ulva may have resulted from greater detection and/or incidental ingestion of amphipods on this plant, due to frequent visitation by fishes. Infrequent visitation of Dictyota by foraging fish also may explain A. longimana's persistence through the summer on this chemically defended seaweed while the two Ulva-associated amphipods declined precipitously. These results (1) confirm that association with chemically defended plants can reduce predation on generalist, as well as specialist, herbivores and (2) suggest that preferential feeding on chemically defended plants is most likely for sedentary mesograzers because low mobility enhances the ability to exploit chemically defended seaweeds as refuges from fish predation.
Feeding preferences of the unusual generalist herbivore Dolabella auricularia, an opisthobranch gastropod which, like many other herbivores of that group, sequesters secondary metabolites from some algae, were consistent with the expectation that they might not feed on algae and seagrasses that were tough, calcified, or chemically rich. Experimental results indicate that Dolabella are indeed relatively unaffected by chemical defenses and yet are deterred by other plant defenses such as calcification and toughness. The fact that Dolabella can sequester algal secondary metabolites may explain its relative indifference to chemically rich plant extracts. -from Authors
The strategy of blade abandonment and simultaneous rapid proliferation (via protoplasmic translocation) is unique to siphonaceous macroalgae owing to their lack of restrictive crosswalls. Siphonalean green algae often dominate the standing stocks and productivity of Caribbean mangrove island environs and are also abundant in virtually all calm-water reef habitats. The experimental organism Avrainvillea longicaulis is particularly abundant in the study sites west of Carrie Bow Cay and Curlew Cay, Belize. The recycling of protoplasm out of older epiphytically impaired blades of A. longicaulis, and simultaneous formation of apical siphon extensions elsewhere, leads to rapid proliferation of new blades--hypothetically, at relatively low energy cost to the plant. The rapidity of siphon extension occurs at least an order of magnitude faster than that possible by photosynthetic production alone, resulting in fully formed proliferations within 3 d. At the same time, the older epiphytized blades become empty, first at the tips, then progressively toward the holdfast, appearing translucent-brown and flaccid within 3 d, followed by senescence. We hypothesize that A. longicaulis rapidly responds to epiphyte colonization/impairment by reallocating protoplasm for new growth through protoplasmic streaming. The alternative hypothesis, that the herbivorous crab Thersandrus compressus might beneficially control epiphytes on A. longicaulis, was falsified by its strong negative effects (i.e., decreased growth and increased host mortality). The hypothesis that allelopathic secondary chemicals may play an antifouling role also was not supported by our experiments; i.e., the consistently vigorous growth rates of the five dominant epiphyte species attached to A. longicaulis were not significantly less than populations of the same species attached to carbonate rock. All of the manipulative results (i.e., experimental induction of blade abandonment followed by new proliferation), as well as the populational survey findings (i.e., greater proliferation by epiphytized plants) and physiological data (i.e., photosynthetic inhibition by epiphytes), support the blade abandonment/proliferation hypothesis, thereby documenting an effective epiphyte-control strategy.
In the last decade, research on the previously dormant field of camouflage has advanced rapidly, with numerous studies challenging traditional concepts, investigating previously untested theories and incorporating a greater appreciation of the visual and cognitive systems of the observer. Using studies of both real animals and artificial systems, this book synthesises the current state of play in camouflage research and understanding. It introduces the different types of camouflage and how they work, including background matching, disruptive coloration and obliterative shading. It also demonstrates the methodologies used to study them and discusses how camouflage relates to other subjects, particularly with regard to what it can tell us about visual perception. The mixture of primary research and reviews shows students and researchers where the field currently stands and where exciting and important problems remain to be solved, illustrating how the study of camouflage is likely to progress in the future.
The hermaeid ascoglossan slug Costasie/la /i/ianae possesses functional sym biotic chloroplasts derived from its algal food, Avrainvil/ea nigricans. Symbiotic plastids continued to fix carbon after 65 days starvation, though efficiency of fix ation declined about 87%. Chlorophyll level did not decline during this period. Degeneration of symbiotic plastids involved swelling and delamination of thy lakoids, increase in electron density of plastids, and decrease in pyrenoid electron density. Plastids within single cells degenerate at about the same time, suggesting that individual cells phagocytize the entire complement of plastids during a brief period. Temperature strongly influenced carbon fixation, both in rate of net fixation and in production of alcohol-insoluble photosynthates. The optimum temperature for fixation was 25°C.Photosynthetic rate exhibited saturation at about 500 se (microeinsteins) . m2 -s@'and substantial fixation occurred at intensities as low as 25 m2@s@.No inhibition occurred in full sunlight (1500 pe.m2.s').
Because feeding specialization among marine herbivores is rare, marine communities provide a simplified system for identifying factors selecting for specialization. On Australia's Great Barrier Reef, we investigated interactions among the chemically-defended seaweed Chlorodesmis fastigiata, herbivores specialized on this alga, and potential predators of these herbivores. Chlorodesmis is a low preference food for reef fishes but appears to be the only food of the crab Caphyra rotundifrons and the ascoglossan gastropods Elysia sp. and Cyerce nigricans. The crab is found only in patches of Chlorodesmis, feeds solely on the alga, and selectively shelters in it in laboratory choice experiments. Crab grazing on the red seaweed Acanthophora spicifera was stimulated when this alga was coated with increasing concentrations of the cytotoxic diterpenoid chlorodesmin, the major secondary metabolite of Chlorodesmis. Crabs did not sequester Chlorodesmis metabolites but avoided predators by sheltering in the unpalatable alga. All crabs tethered on the reef without access to Chlorodesmis patches were rapidly eaten; those with access to Chlorodesmis patches were much less susceptible to predation. The cryptic ascoglossan Elysia sp. was found exclusively in patches of Chlorodesmis and sequestered metabolites from the alga. Living Elysia were unpalatable to the common wrasse Thalassoma lunare in laboratory assays, but the crude organic extract of Elysia did not significantly deter feeding by Thalassoma. Elysia sequestered chlorodesmin, which deterred feeding by reef fishes in field assays but was ineffective against Thalassoma in laboratory assays at 5% food dry mass. Unlike Elysia, the aposematically colored ascoglossan Cyerce nigricans sequestered Chlorodesmis metabolites in relatively small amounts, but produced larger amounts of unrelated polypropionate compounds. Cyerce were never attacked by fishes and the crude organic extract of this slug strongly deterred feeding by wrasses in laboratory assays. The dorid nudibranch Gymnodoris sp. was found only in Chlorodesmis patches and appeared to be a specialized predator on Elysia; it would not prey on Cyerce. Data from this and other recent investigations demonstrate that some small marine herbivores feed selectively or exclusively on seaweeds that are chemically defended from fishes. This association reduces predation on the herbivores and suggests that escape from and deterrence of predation may be a dominant factor selecting for specialization among these herbivores.
Two new metabolites of an apparent propionate origin have been isolated from the organic extract of the ascoglossan molluscCyerce nigricans. The proposed structures for the new natural products are based on interpretation of their physical and spectral properties. The new compounds isolated lacked the potent ichthyodeterrent properties of the whole animal extract suggesting that other molecules are involved in the defense of this shell-less mollusc.
The potential role of generalist natural enemies is presented as one of the important ecological pressures that select for narrow host range in phytophagous insects, and dominant relative to physiological bases for specialization. Experiments are described in three completely different systems indicating that generalist herbivores are more vulnerable to predation than specialist herbivores. The three predators were (a) the vespid waspMischocyttarus flavitarsus, (b) the Argentine antIridomyrmex humilis and (c) the coccinellid beetleHippodamia convergens. It is concluded the predators may provide strong selection pressure for maintenance and perhaps evolution of narrow host range in insect herbivores.
We argue that generalist natural enemies of herbivorous insects provide a major selection pressure for restricted host plant range. The significance of plant chemistry is discussed in terms of regulating behavior, while the chemical coevolutionary theories are considered to be of limited value.
Kelp forests along the coast of central California harbor juvenile rockfish that prey on the larvae of invertebrates from the rocky intertidal zone. This predation reduces recruitment to barnacle populations to 1/50 of the level in the absence of fish. The dynamics of the intertidal community are thus strongly coupled to the dynamics of the offshore kelp community.
The results of the first series of multidisciplinary investigations of this Caribbean barrier reef complex are reported in 33 papers, all abstracted separately. The first section treated the structure of barrier reef habitats in the vicinity of the Cay; influential physical parameters; geological and sedimentological history of lagoon, reefs, and island substrates; and the island's environment. Subsequent papers analyze the distribution of endolithic microorganisms in carbonate substrates, and the diversity, standing crop, and production in selected lagoon and back-reef habitats. Related contributions report on benthos and surface zooplankton. One section is devoted to the systematics and local distribution of flora and fauna. A section on ecological responses discusses the reaction of algae to grazing pressure, the life history of an ichthyo-parasitic hydroid, the growth response of the reef coral Montastrea annularis to a light gradient, and associations between zoanthids and their sponge hosts. The volume concludes with 2 general surveys of the barrier reef and cays.- from Editors
Seasonal changes in the intertidal distribution, abundance and population dynamics of the epifaunal amphipod Gammarus palustris were studied in salt marshes bordering 2 estuarine rivers flowing into the Chesapeake Bay. The amphipod populations inhabiting the Patuxent River study site showed abundance peaks during the spring and autumn, and major declines in density during the summer and winter. Populations at 2 study sites in the Rhode River showed only 1 peak of abundance during the late spring and early summer which was followed by a decline in density throughout the remainder of the year. In both rivers, the low amphipod densities observed during the winter corresponded with a subtidal migration. Migrations did not account for the low numbers observed at other times and an examination of the life cycle of this species as well as an egg-ratio analysis of the populations indicated that low densities during the summer (Patuxent) or late summer and fall (Rhode) were not due solely to life-cycle events. The tolerance of G. palustris to 3 environmental parameters was tested in the laboratory. These included low-salinity, heat/desiccation and freezing-stress experiments. Comparisons of the results with observed fluctuations of these variables at the study sites demonstrated that only freezing stress would probably cause significant mortality in intertidal populations of this species. Insufficient tolerance to this stress was postulated as the reason for the observed distributional shift to subtidal areas during the winter. Amphipod distribution within the intertidal zone at other times of the year was highly correlated with Spartina density. Substratum preference experiments indicated that this was due to a strong behavioral preference by this species for Spartina culms. Intraspecific and interspecific competition for food were tested by an analysis of 3 reproductive indices: the estimated birth rate as calculated by the egg-ratio method, the average brood size and the average brood size/ovigerous @V. The former 2 indices declined during the early summer as a result of natural adult female mortality and a decreased proportion of ovigerous to nonovigerous @V @V. The average brood size/ovigerous @V did not decline significantly throughout the reproductive period indicating that food limitation did not induce the observed summer decline in amphipod abundance. Intraspecific competition for space was tested in the laboratory by crowding and competitive-displacement experiments. The results indicated that competition for space was not directly responsible for the summer decrease in amphipod density but did influence amphipod distribution when Spartina culms were a limited resource. In this situation, G. palustris was capable of intraspecific displacement and evidence is presented which indicates that adults are able to displace juveniles from the preferred substratum. Interspecific competition was not examined experimentally because most of the associated fauna inhabiting the marsh beds were infaunal species. Laboratory predation experiments showed that 3 species, Fundulus heteroclitus, Rhithropanopeus harrisii and Paleomonetes pugio could potentially regulate G. palustris densities. Furthermore, F. heteroclitus predation decreased significantly with increased Spartina density and was strongly size selective for large amphipods. Rhithropanopeus harrisii and P. pugio predation was not significantly affected by Spartina density when amphipod abundance was low and predation by both species was significant with high amphipod and culm density, similar to that observed at the Rhode River sites. Although adult R. harrisii showed some indication of size selective predation, neither species was strongly size selective for large G. palustris when Spartina culms were dense. Field caging experiments combined with estimates of predator density indicated that Fundulus predation was the primary source of mortality in the Patuxent River population during the summer. The results of caging experiments in the Rhode River were inconclusive but large increases in predator density correlated with major declines in amphipod abundance. Therefore, predation is postulated as the major source of mortality during the summer and fall at the Rhode River sites. Thus, both environmental and biological factors regulate these amphipod populations with the former important during the winter only and the latter important at other times of the year.
The ascoglossan (= sacoglossan) opisthobranchMourgona germaineae Marcus secretes a viscid mucus and autotomizes cerata when mechanically disturbed. Other small invertebrates, i.e., sea anemones, amphipods, and other ascoglossans, will die when placed with these autotomized cerata or in the water in which they have been autotomized. The toxin is methanol-soluble and water-soluble and thus is probably a small molecule. Simultaneous TLC of chloroform and methanol-water extracts ofM. germaineae and of its food alga,Cymopolia barbata indicates that the toxin is most likely of dietary origin.
Adults of a generalist herbivore, the lubber grasshopper,Romalea guttata, can be converted to functional specialists by feeding them exclusively on catnip,Nepeta cataria. No obvious adverse effects on adult development resulted from this enforced monophagy. Notwithstanding the fact thatR. guttata has had no coevolutionary relationship with this Eurasian mint, it readily sequesters compounds that are identical to or derived from the terpenoid lactones that are characteristic ofN. cataria. R. guttata appears to both biomagnify minor allelochemicals and to sequester metabolites of theNepeta terpenes in its paired defensive glands. The levels of autogenously produced phenolics are not affected by feeding onN. cataria and the defensive secretions of catnip-fed grasshoppers are more repellent to ants than those of wild-fed acridids. Metabolites of theN. cataria monoterpenes are sequestered in the defensive glands when catnip is added to the natural diet ofR. guttata. The ability of a generalist,R. guttata, to facilely bioaccumulate a potpourri of foreign allelochemicals when feeding in a specialist mode is analyzed in terms of its biochemical, physiological, and functional significance. Sequestration is examined as a response to the enteric effronteries represented by the phytochemicals that can be characteristic of the "overload" in a monophagous diet.
Adults of four abundant species of phytal ampithoid amphipod which occur sympatrically at Fancy Point, Tasmania, were found to partition the environment by size and plant species. A series of motility, predation, and algal selection experiments was carried out to help explain the observed distribution and life-history patterns of these animals. The restricted distributions among algae of two of these amphipods were exceptional for animals within the phytal community but followed a general pattern of increasing specialization of amphipods as the number of co-occurring congeneric species increased.
Aspects of the relationship between the amphipods found associated with eelgrass (Zostera marina L.) and the common predators of this habitat have been examined by laboratory experiments and field sampling. Laboratory experiments showed that of the most abundant potential predators on eelgrass amphipods, the pinfish Lagodon rhomboides (L.) and the grass shrimp Palaemonetes vulgaris (Say) were amongst the most effective predators. Selective feeding by these two species with respect to prey species, size, and sex was demonstrated. Habitat complexity was shown to play a major rôle in the predatory effectiveness of the pinfish and grass shrimp. An examination of the field data in the light of the laboratory selection experiments suggests that the presence of pinfish may 1.1) determine the relative abundances in the community of different types of amphipod species,2.2) determine seasonal changes in species diversity by selectively removing certain species, and3.3) to some degree, through an interaction with habitat complexity, determine the spatial distribution of amphipod abundance and diversity within eelgrass beds.
Published studies of consumer feeding preferences using foods that experience autogenic change in mass, numbers, area, etc., on the time scale of a feeding trial fail to employ appropriate statistical analyses to incorporate controls for those food changes occurring in the absence of the consumer. The studies that run controls typically use them to calculate a constant "correction factor", which is subtracted prior to formal data analysis. This procedure constitutes a non-rigorous suppression of variance that overstates the statistical significance of observed differences. The appropriate statistical analysis for preference tests with two foods is usually a simple t-test performed on the between-food differences in loss of mass (or numbers, area, etc.) comparing the results of experimentals with consumers to controls without consumers. Application of this recommended test procedure to an actual data set illustrates how low replication in controls, which is typical of most studies of feeding preference, inhibits detection of an apparently large influence of previous mechanical damage (simulated grazing) in reducing the attractiveness of a brown alga to a sea urchin.
A new brominated diphenylmethane derivative, avrainvilleol, has been isolated from the green alga Avrainvillea longicaulis, and its structure determined by chemical and spectral methods. Avrainvilleol was toxic toward reef fishes at 10 μg/ml levels, showed antibacterial activity and at 800 ppm induced significant feeding deterrence in the tropical damselfish Pomacentrus coeruleus.
Between-habitat differences in macrophyte consumption by herbivorous fishes were examined on three Caribbean and two Indian Ocean coral reefs. Transplanted sections of seagrasses were used as a bioassay to compare removal rates in reef-slope, reef-flat, sand-plain, and lagoon habitats. Herbivore susceptibility of fifty-two species of seaweeds from these habitats was also measured in the field. Seagrass consumption on shallow reef slopes was always significantly greater than on shallow reef flats, deep sand plains, or sandy lagoons. Reef-slope seaweeds were consistently resistant to herbivory while reef-flat seaweeds were consistently very susceptible to herbivory. This pattern supports the hypothesis that defenses against herbivores are costly in terms of fitness and are selected against in habitats with predictably low rates of herbivory.Sand-plain and lagoon seaweeds showed a mixed response when placed in habitats with high herbivore pressure; most fleshy red seaweeds were eaten rapidly, most fleshy green seaweeds were eaten at intermediate rates, and most calcified green seaweeds were avoided or eaten at very low rates. Differences in susceptibility between red and green seaweeds from sand-plain or lagoon habitats may result from differential competitive pressures experienced by these seaweed groups or from the differential probability of being encountered by herbivores. The susceptibility of a species to removal by herbivorous fishes was relatively consistent between reefs. Preferences of the sea urchin Diadema antillarum were also similar to those of the fish guilds.Unique secondary metabolites were characteristic of almost all of the most herbivore resistant seaweeds. However, some of the herbivore susceptible species also contain chemicals that have been proposed as defensive compounds. Genera such as Sargassum, Turbinaria, Thalassia, Halodule, and Thalassodendron, which produce polyphenolics or phenolic acids, were consumed at high to intermediate rates, suggesting that these compounds are not effective deterrents for some herbivorous fishes. Additionally, potential for the production of the compounds caulerpin, caulerpicin and caulerpenyne in various species of Caulerpa did not assure low susceptibility to herbivory.Heavily calcified seaweeds were very resistant to herbivory, but all of these species also produce toxic secondary metabolites which makes it difficult to distinguish between the effects of morphological and chemical defenses. Predictions of susceptibility to herbivory based on algal toughness and external morphology were of limited value in explaining differing resistances to herbivory.
Marine mollusks of the Order Ascoglossa (= Sacoglossa) are specialized herbivores of tropical green seaweeds and other seaweeds (diatoms, red algae, seagrasses). In this study, we investigated the feeding relationship between the ascoglossan Elysia halimedae Macnae and its preferred food, the seaweed Halimeda macroloba Decaisne. The toxic diterpenoid metabolites of many species of Halimeda have been shown to act as feeding deterrents toward nonspecialized grazers such as herbivorous fishes. However, E. halimedae feeds only on species of Halimeda and prefers young plant growth, which contains the highest concentrations of the Halimeda compounds. Our observations suggest that E. halimedae modifies the major diterpenoid from H. macroloba and sequesters and stores this modified compound for its own defense. When irritated, Elysia secretes large amounts of mucus containing this defensive compound. The compound occurs in Elysia as ≈ 7% of the whole animal dry mass. Similar high concentrations of the compound are found in the egg masses of E. halimedae. We isolated and determined the structure of the ascoglossan compound and tested the compound in field assays toward carnivorous and herbivorous fishes on Guam. This compound is a significant feeding deterrent at naturally occurring concentrations toward potential predators. Thus, E. halimedae is adapted to feed on toxic algae and utilizes the algal chemical defenses for its own defense against predation.
Thesis (Ph. D.)--University of Maryland, 1977. Includes bibliographical references (p. 97-102). Photocopy.
The green sacoglossan gastropod Oxynoe panamensis occurs in mangrove swamps on the coasts of Baja Californi a, Mexico, apparently feeding exclusively on the green siphonaceous alga Caulerpa sertularioides . When irritated, it secretes an astringent, milky mucus, which contains a toxin lethal to fish. Continued molestation may induce autotomy of the tail.
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