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Coral-Reef Asteroids of Guam
Abstract
Most coral-reef asteroids of Guam, at least 24 species in total, represent those which are widely distributed in the Indo-West Pacific. The diversity of asteroid fauna in Micronesia and its surrounding region follows a general trend of a faunal center in the rich Indo-Malayan Archipelago area with the number of species diminishing eastward in the scattered and remote oceanic islands. Larval development in many common reef asteroids is oriented toward dispersion by producing planktotrophic and surface-floating larvae which stay in the pelagic environment for three weeks or longer. The major oceanic surface currents flow westward, driven by steady trade winds in the area surrounding Guam and most of the Micronesian Islands. It is argued that local recruitment of asteroid populations might be hazardous under such circumstances where coastal water masses would hardly conserve larval populations inshore. Juvenile populations of reef asteroids have been rarely located in the field, in spite of conspicuous adult populations. Feeding habits, life histories, and other aspects of natural histories of reef asteroids are discussed.
... The arms are thick and slender with blunt tips (Clark and Rowe 1971). They have a thick epidermis and a heavily calcified skeleton (Yamaguchi 1975). This species was observed in all study sites except in Camudmud and Kaputian. ...
... The occurrence of the species was reported in Talikud Choriaster granulatus C. granulatus has a smooth body texture and developed arms that are short and stout (Clark and Rowe 1971). Although the body of C. granulatus appears smooth, it has a thick and calcified skeleton (Yamaguchi 1975). Yamaguchi (1975) added that they usually stay on fully exposed reef flats hence, the need for a more robust skeleton. ...
... Although the body of C. granulatus appears smooth, it has a thick and calcified skeleton (Yamaguchi 1975). Yamaguchi (1975) added that they usually stay on fully exposed reef flats hence, the need for a more robust skeleton. Two distant individuals were observed on coral rubble in the low intertidal zone and shallow waters. ...
Echinoderms are immediately observable around the coastal shores of Samal Island. Unfortunately, studies on echinoderm diversity are lacking despite its relevance to coastal
and marine ecosystems management. This study attempts to update the existing records of echinoderms in Samal Island, however, limited to the intertidal and shallow-water areas. Field surveys from January 2018 to January 2019 yielded a total of 30 echinoderm species belonging to 17 families. Most of the echinoderms encountered belonged to Classes Asteroidea (sea stars, nine species) and Ophiuroidea (brittle stars, nine species), followed by Echinoidea (regular and irregular urchins, six species) and Holothuroidea (sea cucumbers, six species). Of the 1,015 individuals, sea urchins comprised the majority of the total individuals recorded (43.15%), succeeded by sea stars (30.44%), brittle stars (18.04%), and sea cucumbers (8.37%). Richest diversity was observed in Catagman with 23 echinoderm species recorded. This was followed by Camudmud (14 species), Pangubatan (eight species), Balet (seven species), Aundanao (six species), and Kaputian (three species). The five most commonly occurring species were the Echinometra mathaei (Blainville, 1825), Archaster typicus (Müller and Troschel, 1840), Ophiocoma scolopendrina (Lamarck, 1816), Diadema setosum (Leske, 1778), and Linckia laevigata (Linnaeus, 1758). Differences in distribution and abundance may be attributed to the variability of habitats available across sites. An intensive biodiversity assessment i recommended to evaluate how the physicochemical parameters and extent of anthropogenic activities shape the diversity and distribution of echinoderms on the island. The current work also provides the first documentation of ophiuroid diversity and the first record of the brittle stars, Breviturma krohi (Stöhr, Boissin & Hoareau, 2013) and Ophiocoma cf. cynthiae (BenavidesSerrato and O’Hara, 2008) in Samal Island, Philippines.
... Seaward reef (Yamaguchi 1975, Jangoux 1982b) ...
... Coral reefs Coral and rock reefs (Yamaguchi 1975, Jangoux 1982b Coral reefs (Yamaguchi 1975, Jangoux 1982b Linckia guildingi (Gray, 1840) 150 15.0 10 Biofilm (substrate feeding on algae and microbes) ...
... Coral reefs Coral and rock reefs (Yamaguchi 1975, Jangoux 1982b Coral reefs (Yamaguchi 1975, Jangoux 1982b Linckia guildingi (Gray, 1840) 150 15.0 10 Biofilm (substrate feeding on algae and microbes) ...
... C. schmideliana occurred throughout all lagoon and fore reef habitats, with highest densities found on the reef flat and reef crest and abundances declining significantly with depth. A preference for shallow parts of the reef has been reported previously (Yamaguchi 1975;Pratchett et al. 2011). In Moorea, C. novaeguineae were restricted to the reef flat, and were absent on the reef crest and reef slope (Pratchett et al. 2011). ...
... ighest densities found on the reef flat and reef crest and abundances declining significantly with depth. A preference for shallow parts of the reef has been reported previously (Yamaguchi 1975;Pratchett et al. 2011). In Moorea, C. novaeguineae were restricted to the reef flat, and were absent on the reef crest and reef slope (Pratchett et al. 2011). Yamaguchi (1975 also found C. novaeguineae on the reef flat, as well as the lagoon and seaward reef in Guam. In contrast, Culcita spp. occurred to at least 30-m depth in this study and to a depth of 20 m in Hawaii (Glynn and Krupp 1986), whereas Goreau et al. (1972) observed the highest abundance and most severe predation on the outer fore reef slope a ...
... The overall size structure had a single mode, with most (89.2%) between 14 and 17 cm in diameter, suggesting that this population originated from a single recruitment event. Yamaguchi (1973Yamaguchi ( , 1975 found that C. novaeguineae transformed from a pentagonal flat juvenile to a cushion-form adult at ,9 cm in diameter and 2 years of age (Yamaguchi 1973(Yamaguchi , 1975. The growth and longevity of adults is unknown, although growth rates for adults are presumed to increase exponentially once they switch from a diet consisting predominantly of algae to corals (Yamaguchi 1973). ...
Culcita spp. are facultative corallivores that can have a selective effect on coral composition due to their feeding preference for Acropora spp. and Pocillopora spp. Although Culcita are normally rare (<0.5 per 100 m²), mean densities of up to 9.2 sea stars per 100 m² were observed on a Maldivian reef system, with the highest numbers on the reef flat and reef crest. Culcita fed on 12 genera of corals, but showed a distinct preference for Pocillopora (51%) and Acropora (21%). Formerly the dominant corals on Maldivian reefs, these genera sustained 80–95% mortality from coral bleaching in 2016. Low numbers of juvenile acroporids and pocilloporids were slowly recolonising the reef, but 24% had recently been eaten by Culcita schmideliana. The abnormal abundance of C. schmideliana and high number of recently dead juvenile corals suggest that chronic predation by C. schmideliana could delay the recovery of reefs damaged by the 2016 mass bleaching event.
... Seaward reef (Yamaguchi 1975, Jangoux 1982b) ...
... Coral reefs Coral and rock reefs (Yamaguchi 1975, Jangoux 1982b Coral reefs (Yamaguchi 1975, Jangoux 1982b Linckia guildingi (Gray, 1840) 150 15.0 10 Biofilm (substrate feeding on algae and microbes) ...
... Coral reefs Coral and rock reefs (Yamaguchi 1975, Jangoux 1982b Coral reefs (Yamaguchi 1975, Jangoux 1982b Linckia guildingi (Gray, 1840) 150 15.0 10 Biofilm (substrate feeding on algae and microbes) ...
Herbivory is an important ecological process controlling community structure and function in almost all ecosystems. The effects of herbivores on algal assemblages depend primarily on consumer and algal traits, but the strength of this interaction is contingent on physical and biological processes. Marine herbivory is particularly intense, where grazers can remove around 70% of primary production. Present understanding of marine herbivory is largely based on well-studied groups including herbivorous fishes, gastropods, crustaceans and sea urchins. Herbivory in other marine taxa is poorly understood, but nonetheless important. For instance, grazing by starfish has the potential to strongly affect algal assemblages. Most starfish feed by extruding their stomach and digesting their food externally. This feeding mechanism is distinctive and complex, and evolutionarily advantageous as it allows individuals to explore many different food sources. Variation in the feeding habits of herbivorous starfish is intriguing because some species are very specialised whereas others are more generalist, and the reasons for those variations are not well understood. Some herbivorous starfish are obligate herbivores while others vary from herbivory to carnivory between life stages or between populations within the same species. The question that then arises is how well we are able to predict grazing pressure from complex feeding habits on benthic systems? This review provides a synthesis of herbivory in starfish showing that: the majority of species forage on microalgae and soft tissue macroalgae; fidelity to an algal diet appears to be related to the size of individuals; and, feeding habits are likely to change with variation in food availability. Directions for future studies on the biology and ecology of herbivorous starfish are suggested to better understand variation in species feeding behaviour. Elucidating the mechanisms that contribute to variation in the behaviour of herbivorous starfish is crucial to predict the effects that these species exert on the structure of marine benthic communities. The influence of omnivorous species also warrants more detailed study. Such investigations are important in the context of climate change, given the potential for species invasions associated with range expansions.
... Clark & Rowe 1971, Marsh 1974. They extrude their tiny stomachs over the substratum and browse the epibenthic film of organic detritus and microorganisms (Yamaguchi 1975, 1977a, Thomassin 1976, Sloan 1980, Jangoux 1982a). The substratum on which feeding takes place is often crustose coralline algae (Laxton 1974a) and a white spot can be seen occasionally in the coralline algae underneath the extruded stomach. ...
... The substratum on which feeding takes place is often crustose coralline algae (Laxton 1974a) and a white spot can be seen occasionally in the coralline algae underneath the extruded stomach. Small encrusting sponges, bryozoans, and ascidians are sometimes browsed by the larger ophidiasterids (Yamaguchi 1975, various authors in Jangoux 1982aand Sloan 1980. Laxton (1974a) found 1 % of the Linckia laevigata feeding on small coral colonies on the Great Barrier Reef and Thomassin (1976) found Nardoa variolata consuming coral mucus at Madagascar. 9 Figure 2. Diagrammatic representation of categories of coral-reef asteroids. ...
... At least nine species of asteroids occasionally prey upon living corals or feed on coral mucus in the Pacific (or at least ten if Acanthaster ellisii is separated from A. planci): Culcita novaeguineae (Endean 1971, Go-reau et al. 1972, Glynn & Krupp 1986), C. schmideliana (Thomassin 1976), Nidorellia armata (Chesher 1972, Glynn & Wellington 1983, Pharia pyramidata (Dana & Wolf son 1970, Glynn & Wellington 1983, Linckia laevigata (Laxton 1974a, Thomassin 1976, Nardoa variolata and Echinaster purpureus (Thomassin 1976), Asterina sp. (Yamaguchi 1975), and Acanthaster planci (Goreau 1964, Pearson & Endean 1969, Branham et al. 1971, Goreau et al. 1972, Endean 1973, Branham 1973, Potts 1981, Moran 1986. Only A. planci and Culcita spp. ...
... mm (Döderlein, 1916;1935). The distribution of this species in the Maldives, Philippine Islands, Guam, Papua New Guinea, Solomon Islands, and Queensland, Australia, was confirmed by Yamaguchi (1975), Rowe & Gates (1995), and Marsh & Fromont (2020). In addition to the distribution records, Marsh & Fromont (2020) noted that the maximum body size of this species was R/r = 46/20 mm. ...
... The small body size of this sea star raises doubts about the validity of the species. Yamaguchi (1975) suspected that this species represents a juvenile form of Choriaster granulatus Lütken, 1869. Clark (1993 pointed out that the validity of the genus Bothriaster and the species B. primigenius was doubtful because the diagnostic characteristics were attributable to the immaturity of the lost holotype specimen. ...
One of the oreasterid sea stars, Bothriaster primigenius, is a rarely encountered species in the tropical Indo-West Pacific. The taxonomic position of this species, and more specifically, whether to recognize this sea star as a species, remains unresolved. To resolve the question, we assessed the specific validity of this sea star based on morphological observations and molecular phylogenetic analysis. The results revealed that this species is a young individual of another oreasterid sea star, Choriaster granulatus, and is placed as a junior synonym for the same.
... Juvenile COTS have been shown to consume CCA for 4 6 months post settlement in laboratory studies [7,29] and for 13-15 months in nature [30]. Similar to COTS, juveniles of the sympatric corallivore Culcita novaeguineae initially consume CCA and biofilms [31] and the temperate species Stichaster australis switches from CCA to bivalve prey at 15-28 months of age [32]. To become a competent corallivore, juvenile COTS need to achieve a minimum size of~8 mm diameter, be able to digest the complex wax esters in coral tissue, and withstand stings from coral polyps [7,30,33]. ...
... However, COTS are able to settle in the absence of CCA [22,35], and are known to have a flexible diet in their larval [36,37] and corallivorous [24,38,39] stages. Juveniles have been reported to eat biofilms [31,40]. Biofilms are a ubiquitous food source in nature and are considered to be a cost-effective food source for juvenile sea stars [28]. ...
The ecology of the early herbivorous juvenile stage of the crown-of-thorns sea star (COTS, Acanthaster spp.) is poorly understood, yet the success of this life stage is key to generating population outbreaks that devastate coral reefs. Crustose coralline algae (CCA) has been considered to be the main diet of herbivorous juveniles. In this study, we show that COTS can avail of a range of algal food. Juveniles were reared on CCA, Amphiroa sp., and biofilm, and survived for 10 months on all three diets. The juveniles fed CCA and Amphiroa sp. reached 15–16.5 mm diameter at ~ 6 months and maintained this size for the rest the experiment (an additional ~4 months). Juveniles fed biofilm grew more slowly and to a smaller maximum size (~3 mm diameter). However, when juveniles were switched from biofilm to CCA they resumed growth to a new asymptotic size (~13.5 mm, 13–20 months). In diet choice experiments, juveniles did not show a preference between Amphiroa sp. and CCA, but generally avoided biofilm. Our results show that juvenile COTS grew equally well on CCA and Amphiroa sp. and can subsist on biofilm for months. Some juveniles, mostly from the biofilm diet treatment, decreased in size for a time and this was followed by recovery. Flexibility in diet, growth, and prolonged maintenance of asymptotic size indicates capacity for growth plasticity in herbivorous juvenile COTS. There is potential for juvenile COTS to persist for longer than anticipated and increase in number as they wait for the opportunity to avail of coral prey. These findings complicate our ability to predict recruitment to the corallivorous stage and population outbreaks following larval settlement and the ability to understand the age structure of COTS populations.
... These questions are LARGELY UNRESOLVED. Early field observations [11] and laboratory experiments [135] suggested that CoTS larvae are unpalatable to planktivorous fishes, such that predation was considered to exert limited influence on These questions are LARGELY UNRESOLVED. Early field observations [11] and laboratory experiments [135] suggested that CoTS larvae are unpalatable to planktivorous fishes, such that predation was considered to exert limited influence on larval mortality. ...
... Early field observations [11] and laboratory experiments [135] suggested that CoTS larvae are unpalatable to planktivorous fishes, such that predation was considered to exert limited influence on These questions are LARGELY UNRESOLVED. Early field observations [11] and laboratory experiments [135] suggested that CoTS larvae are unpalatable to planktivorous fishes, such that predation was considered to exert limited influence on larval mortality. CoTS larvae contain steroidal saponins, which may have specific anti-predatory functions, as demonstrated by experimental assays showing planktivorous fishes discriminating against saponin-impregnated food pellets [136]. ...
... These questions are LARGELY UNRESOLVED. Early field observations [11] and laboratory experiments [135] suggested that CoTS larvae are unpalatable to planktivorous fishes, such that predation was considered to exert limited influence on These questions are LARGELY UNRESOLVED. Early field observations [11] and laboratory experiments [135] suggested that CoTS larvae are unpalatable to planktivorous fishes, such that predation was considered to exert limited influence on larval mortality. ...
... Early field observations [11] and laboratory experiments [135] suggested that CoTS larvae are unpalatable to planktivorous fishes, such that predation was considered to exert limited influence on These questions are LARGELY UNRESOLVED. Early field observations [11] and laboratory experiments [135] suggested that CoTS larvae are unpalatable to planktivorous fishes, such that predation was considered to exert limited influence on larval mortality. CoTS larvae contain steroidal saponins, which may have specific anti-predatory functions, as demonstrated by experimental assays showing planktivorous fishes discriminating against saponin-impregnated food pellets [136]. ...
Research on the coral-eating crown-of-thorns starfish (CoTS) has waxed and waned over the last few decades, mostly in response to population outbreaks at specific locations. This review considers advances in our understanding of the biology and ecology of CoTS based on the resurgence of research interest, which culminated in this current special issue on the Biology, Ecology and Management of Crown-of-Thorns Starfish. More specifically, this review considers progress in addressing 41 specific research questions posed in a seminal review by P. Moran 30 years ago, as well as exploring new directions for CoTS research. Despite the plethora of research on CoTS (>1200 research articles), there are persistent knowledge gaps that constrain effective management of outbreaks. Although directly addressing some of these questions will be extremely difficult, there have been considerable advances in understanding the biology of CoTS, if not the proximate and ultimate cause(s) of outbreaks. Moving forward, researchers need to embrace new technologies and opportunities to advance our understanding of CoTS biology and behavior, focusing on key questions that will improve effectiveness of management in reducing the frequency and likelihood of outbreaks, if not preventing them altogether.
... Conversely, crown-of-thorns starfish have well-developed physical and chemical predatory defences and are considered to be largely immune from predation (Lucas et al. 1979;Gladstone 1992). Eggs and larvae of crown-of-thorns starfish have particularly high concentrations of saponins (Barnett et al. 1988), which have been directly implicated in defence against predators (Yamaguchi 1974(Yamaguchi , 1975Voogt and Van Rheenen 1979). ...
... Endean 1969;Campbell and Ormond 1970;Dulvy et al. 2004). This is mainly attributable to the widely held assumption that few (if any) potential predators will eat eggs or larvae of crownof-thorns starfish based on early research that demonstrated the toxicity of saponins (Mackie et al. 1977) and complete avoidance of larvae of crown-of-thorns starfish by planktivorous fishes (Yamaguchi 1974(Yamaguchi , 1975 recent experimental studies (e.g. Cowan et al. 2016) indicate that pre-settlement life stages of crown-of-thorns starfish are indeed vulnerable to predation. ...
Coral-eating crown-of-thorns starfish (Acanthaster sp.) often exhibit dramatic population outbreaks, suggesting that their local abundance may be relatively unchecked by predators. This may be due to high concentrations of anti-predator chemicals (saponins and plancitoxins), but the effectiveness of chemical deterrents in protecting Acanthaster sp., especially spawned eggs, from predation remains controversial. We show that planktivorous damselfishes will readily consume food pellets with low proportions (≤80%) of eggs of crown-of-thorns starfish. However, all fishes exhibited increasing rejection of food pellets with higher proportions of starfish eggs, suggesting that chemicals in eggs of crown-of-thorns starfish do deter potential predators. Interestingly, palatability thresholds varied greatly among the nine species of planktivorous fish tested. Most notably, Amblyglyphidodon curacao consumed food pellets comprising 100% starfish eggs 1.5 times more than any other fish species, and appeared largely insensitive to increases in the concentration of starfish eggs. After standardising for size, smaller fish species consumed a disproportionate amount of pellets comprising high proportions of starfish eggs, indicating that abundant small-bodied fishes could be particularly important in regulating larval abundance and settlement success of crown-of-thorns starfish. Collectively, this study shows that reef fishes vary in their tolerance to anti-predator chemicals in crown-of-thorns starfish and may represent important predators on early life-history stages.
... Unlike coral eggs, which are heavily preyed upon by planktivorous fish (Westneat and Resing 1988), laboratory studies suggest that the eggs and larvae of A. planci are generally rejected or avoided by fish and invertebrate predators (Yamaguchi 1975), probably due to high saponin concentrations (Lucas et al. 1979). However, field observations of predation on A. planci gametes by fish have been made during spawning: eggs eaten by Abudefduf curacao on the Great Barrier Reef (Pearson and Endean 1969), and sperm eaten by Chaetodon auripes in Okinawa (Keesing, personal observation). ...
... Large-scale fluctuations in the populations of these other species have not been recorded, although, like many starfish species, each can be locally common or rare (e.g. Yamaguchi 1975). ...
It has often been regarded that the greatest influence on population dynamics of invertebrate broadcast spawners will be physical and biological processes acting to control the dispersal and survival of the larval or presettlement phase rather than any process acting after settlement. This has been particularly so with the crown-of-thorns starfish, Acanthaster planci, due to its enormous fecundity and the consequent potential for small changes in rates of larval survival to greatly influence subsequent settlement. However, consideration of the biological, behavioural and habitat characteristics of newly settled and juvenile starfish shows that post settlement processes will be equally, if not more, important in determining population size. We hypothesize that larvae will be influenced to a greater extent by physical than biotic factors, particularly by hydrodynamics that can determine whether competent larvae will encounter reefs. In contrast, we argue that settling larvae and juveniles will be more influenced by predation because of their slow growth and movement, dependence on local food availability, and relatively long juvenile phase. Measurement of mortality rates in the field and isolating settlement from recruitment are identified as having high priorities for future research.
... Following their ontogenetic transition from herbivore to corallivore, CoTS exhibit rapid growth supported by their energy-rich coral diet (Fig. 2;Lucas 1984;Zann et al., 1987). Adults exhibit diet plasticity, preying on diverse coral species, consuming alternate prey (e.g., soft corals, bivalves, algae) when coral declines (Yamaguchi 1975;Keesing 1990;Kuo et al., 2022), and exhibiting prey-dependent migration (~20 m day − 1 ) to aggregate around preferred species as coral declines (Ling et al., 2020). Adult CoTS upregulate immune responses which may counter pathogen transmission at high density (i.e., outbreaks; Mills 2012), and are physically and chemically defended, so predation risk is low and restricted to a few specialists (Cowan et al., 2017). ...
... Following coral destruction, A. cf. solaris have been observed to feed on hydrozoans, soft corals, alcyonarians, clams and even anemones (Chesher, 1969;Pearson and Endean, 1969;Branham, 1973;Yamaguchi, 1975), displaying this feeding behaviour close to the end of outbreaks when coral cover is depleted (De'ath and Moran, 1998b). On the other hand, a strong avoidance of the hydrocoral Millepora observed in the Indo-Pacific (Glynn, 1990;Pratchett et al., 2014) helped to create predator-free sanctuaries for scleractinians during outbreaks in French Polynesia (Kayal and Kayal, 2017). ...
... Acanthaster planci are not conclusively corallivores, but may be fed on fish, squid, and scallop meat as well as beef or even their own species (Branham, 1973;Yamaguchi, 1975;Moran, 1986;1998). It is likely that these foods are only eaten in captivity and would not be common food sources in the field. ...
Feeding preferences is important to elucidate ecological interaction between Starfish (Acanthaster planci) and corals to control the population. Four primary growth forms of coral were observed on the study site are branching, tabulate, plate and solitary. However, this four growth form does not show the exact growth form presence in both islands but particular area which has patches of A. planci scars. Overall, in Karah Island, only branching coral was recorded to have scars, while in Ekor Tebu Island, branching and plate growth forms were observed to have scars. Apart from them, there are no preferences on other form of coral. A. planci also showed no preferences on particular size classes on coral they preyed upon. Other factors might influence the preferences of prey chosen by A. planci. Therefore, a better method of assessment could involve a comparison at the coral colony level, such as at genus level, rather than at the community level.
... While mortality of corals in response to warming indicates that the future of COTS is bleak due to the demise of its prey, this sea star has flexibility in its diet at the initial herbivorous juvenile stage availing of a range of food sources, including biofilms (Deaker, Agüera, et al., 2020;. In addition, adult COTS prey on soft corals, bivalves and algae when hard coral availability is low (Chesher, 1969;Kuo et al., 2022;Yamaguchi, 1975). As seen for several ecologically important predatory sea stars Nauen, 1978), juvenile COTS can remain in their recruitment-nursery habitat for a variable amount of time where they exist on an algal diet before they transition to the corallivorous adult stage (Wilmes, Schultz, et al., 2020). ...
The juveniles of predatory sea stars can remain in their recruitment–nursery habitat for some time before their ontogenetic shift to the adult habitat and diet. These small juveniles are vulnerable to a range of factors with their sensitivity amplified by climate change‐driven ocean warming. We investigate the thermal tolerance of the waiting stage herbivorous juveniles of the keystone coral predator, the crown‐of‐thorns sea star (COTS, Acanthaster sp.), in context with the degree heating weeks (DHW) model that predicts coral bleaching and mass mortality. In temperature treatments ranging from +1 to 3°C in prolonged heatwave acclimation conditions, the juveniles exhibited ~100% survival in DHW scenarios that trigger coral bleaching (4 DHW), resulting in mass mortality of corals (8 DHW) and extreme conditions well beyond those that kill corals (12 DHW). This indicates that herbivorous juvenile COTS are far more resistant to heatwave conditions than the coral prey of the adults. The juveniles exhibited higher activity (righting) and metabolic rate after weeks in increased temperature. In separate acute temperature experiments, the upper thermal limit of the juveniles was 34–36°C. In a warming world, juvenile COTS residing in their coral rubble nursery habitat will benefit from an increase in the extent of this habitat due to coral mortality. The juveniles have potential for long‐term persistence as herbivores as they wait for live coral to recover before becoming coral predators, thereby serving as a proximate source of COTS outbreaks on reefs already in a tenuous state due to climate change.
... For many predatory sea stars, larval settlement is promoted by coralline algae and algal/microbial biofilms that in turn also provide a food source for very early juveniles (Yamaguchi, 1974(Yamaguchi, , 1975Barker, 1979;Martinez et al., 2017). In New Zealand, Stichaster australis remains associated with coralline algae for 15-28 months before migrating to mussel beds, where it initiates the predatory phase (Barker, 1979). ...
Growth and recruitment of the sea star Marthasterias glacialis was followed over six years in Lough Hyne, southwest Ireland. Juveniles from a 2-mm radius were found on algae at <1-2-m depth following what appeared to be gregarious larval settlement. Data from Lough Hyne and Mulroy Bay (northwest Ireland) indicated that algal habitat serves as a nursery area for juveniles of M. glacialis. Successive size frequency modes of the juveniles at Lough Hyne indicated slow growth over 6 years, to a mean radius of 20 mm. The absence of additional recruitment allowed monitoring of a discrete population. Recruits in the nursery habitat over the six years remained as waiting stage juveniles, a Peter Pan group with delayed maturity subsisting on a diet of epibionts. An initial sharp decline in numbers indicated post-settlement mortality, with subsequent decline likely due to migration to the adjacent shelly habitat, where subadult M. glacialis (30-70-mm radius) lives. In this habitat, M. glacialis preys on small bivalves and eventually joins the adult (maximum radius = 280 mm) population on open sediment, where it feeds on large bivalves. Size frequency distributions of the juveniles and adults showed growth over the six years, with the waiting stage sea stars slowly merging in size with the adult population. It appears that the supply of new individuals into the adult population may take place six or more years following settlement. Strong connectivity between life stage habitats and prolonged recruitment into the adult population may contribute to balanced exploitation of infaunal prey.
... Komatsu (1973) describes a single L. leachi sea star in an aquarium, which released eggs for ~ 1 h from the dorsal-lateral parts of the arms (August 11, 1972, at 10:00 h). Very little is known about the reproduction and development of these sea stars-and tropical sea stars in general (Bos et al. 2008)-except that both species appear to produce relatively small eggs (~ 140 µm diameter) and have a planktonic-feeding larval stage (Yamaguchi 1975;Chia et al. 1993). ...
On the evenings of June 11 and 12, 2019, 5 and 6 days before full moon, broadcast spawning by four echinoderm species and two mollusc species was observed on the Marsa Shagra reef, Egypt (25° 14′ 44.2" N, 34° 47′ 49.0" E). Water temperature was 28 °C and the invertebrates were observed at 2–8 m depth. The sightings included a single basket star Astroboa nuda (Lyman 1874), 2 large Tectus dentatus (Forskal 1775) sea snails, 14 individuals of the Leiaster cf. leachi (Gray 1840) sea star and 1 Mithrodia clavigera (Lamarck 1816) sea star, 3 Pearsonothuria graeffei (Semper 1868) sea cucumbers, and 2 giant clams, Tridacna maxima (Röding 1798). The observations presented here provide relevant information on broadcast spawning of non-coral invertebrate taxa in the Red Sea, where spawning is considerably less well documented than in other tropical geographical regions such as the Indo-Pacific and Caribbean.
... These questions are LARGELY UNRESOLVED. Early field observations (Pearson and Endean 1969) and laboratory experiments (Yamaguchi 1975) suggested that CoTS larvae are unpalatable to planktivorous fishes, such that predation was considered to exert limited influence on larval mortality. CoTS larvae contain steroidal saponins which may have specific anti-predatory functions, as demonstrated by experimental assays showing planktivorous fishes discriminating against saponin-impregnated food pellets (Lucas et al. 1979). ...
Research on the coral-eating crown-of-thorns starfish (CoTS) has waxed and waned over the last few decades, mostly in accordance with the occurrence of population outbreaks at key locations, such as Australia’s Great Barrier Reef. This review considers advances in our understanding of the biology and ecology of CoTS based on the latest resurgence of research interest, which culminated in this current special issue on the Biology, Ecology and Management of Crown-of-Thorns Starfish. More specifically, this review considers progress against 41 specific research questions posed in the seminal review by P. Moran 30 years ago, as well as exploring new directions for CoTS research. Despite the plethora of research on CoTS (>1,200 research articles), there are persistent knowledge gaps that constrain effective management of outbreaks. Although directly addressing some of these questions will be extremely difficult, there have been considerable advances in understanding the biology of CoTS, if not the proximal and ultimate cause(s) of outbreaks. Moving forward, researchers need to embrace new technologies and opportunities to advance understanding of CoTS biology and behaviour, with focus given to key questions that will improve effectiveness of management to reduce the frequency and likelihood of future outbreaks, if not preventing them altogether.
... Unlike coral eggs, which are heavily preyed upon by planktivorous fishes , Acanthaster spp. gametes and larvae are often avoided by planktivorous fishes and invertebrates (Yamaguchi 1975;Gladstone 1992). Chemical analyses by Lucas et al. (1979) showed that eggs and larvae of Acanthaster spp. ...
Nha Trang Bay (NTB), located off the south-east coast of Vietnam, is a famous tropical tourist site. In the past, the bay was characterised by flourishing coral reefs but, by the end of 2019, more than 90% of the corals were gone. In addition to chronic and complex anthropogenic effects, there was an extensive outbreak of crown-of-thorns starfish (Acanthaster planci), the main natural predator of reef-building corals in the Indo-Pacific, among the remnant coral communities in NTB. By 2019, the mean abundance of A. planci in NTB reached 4.2 starfish per 100 m². Coral surveys conducted on 10 target sites over a 3-year period ending in 2019 revealed that mean coral cover decreased by 64.4% (coral loss varied from 43 to 95%). The greatest declines were in Acropora and Montipora, with 80.6 and 82.3% reductions in the coverage of these taxa respectively. The combination of nutrient enrichment and predator removal is thought to determine the extent of the outbreak of A. planci in the bay. The present trends in environmental conditions in NTB do not indicate a positive outcome for coral reef recovery in in this area in the near future.
... Relationship between the size of the scars produced by Culcita sp. on the preyed coral colonies and the size of the eaten colonies reefs in protected areas (Goreau et al., 1972;Yamaguchi, 1975;Grosenbaugh, 1981;Glynn & Krupp, 1986). However, in line with our observations, C. novaeguineae always displayed a higher density on the reef slopes below 3 and 7 m (Goreau et al., 1972;Glynn & Krupp, 1986). ...
Although corallivory is recognized as a threat affecting the structure and integrity of coral reef habitats, ecological data on most species of coral consumers remain limited, slowing down the development of conservation and restoration strategies of the reef ecosystems. In this study, the population distribution and corallivorous behaviour of the cushion sea star Culcita sp. were investigated in the south region of Faafu Atoll, Maldives. Most sea stars were found on reef slopes within 0–10 m depth and in areas characterized by low live coral cover. Several coral genera were preyed on by the sea star. Although most of the consumed corals belong to the genus Acropora, a feeding preference for the genera Pocillopora and Pavona and a consistent avoidance of the genus Porites were observed. Furthermore, the majority of the prey corals were small colonies (< 10 cm diameter), even though Culcita sp. appeared to be capable of partially consuming larger colonies. Dietary preferences for specific coral colonies or genera have the potential to generate local shifts in coral community composition and structure and may affect reef recovery following natural and anthropogenic disturbance in an already impacted environment such as the Maldivian reefs.
... Prior to settlement, released gametes, swimming larvae, and late brachiolaria searching for suitable settlement substrates must avoid predation. Unlike coral eggs, which are heavily preyed upon by planktivorous fishes, A. planci gametes and larvae are often avoided upon visual recognition or rejected after tasting by fish and invertebrate predators (Yamaguchi, 1974(Yamaguchi, , 1975. Laboratory experiments by Lucas et al. (1979) showed that eggs and larvae contain saponins, which act as chemical defenses detected by and unpalatable to planktivorous fish. ...
The phylum Echinodermata contains some of the most charismatic benthic marine invertebrates and has become a symbol of marine life. However, growing global pressures on the collection of echinoderms for various commercial enterprises have put these enigmatic invertebrates under threat. This review summarises the demands on echinoderms from commercial fisheries, aquarium and souvenir trades, as part of the global search for bioactive compounds from marine organisms, and as experimental models in evolution and toxicology, and highlights the urgent need for an integrated global strategy for their protection and conservation. Sea urchins and sea cucumbers are fished commercially worldwide. Increased landings, limited information on population biology and lack of stringent management of the fisheries have resulted in a global decline of populations. In addition to being a target species for commercial fishing, many echinoderms form part of the significant by-catch produced from the general use of fishing hardware. Even when they are not caught directly, echinoderms may be damaged to varying degrees as the gear passes over them and may be affected indirectly by the physical disturbance caused by fishing gear to the seafloor. Echinoderms are gaining popularity with aquarists and account for about 17% of the global trade. Pharmaceutical companies are constantly screening marine organisms for biochemical compounds for potential use in medicine, traditional healing and industrial applications. The marine bioprospecting industry is not regulated and, although at an early stage of development, the huge potential of echinoderms to provide bioactive products highlights the need for urgent action to regulate this kind of activity. Echinoderm embryos and larvae have been used as experimental model systems in several lines of research for more than a century, leading to significant advances in the areas of developmental biology, cell biology and immunology. In addition, echinoderms are well known for their striking regenerative capacity and have provided a valuable experimental model to identify the genes involved in the process of neural regeneration. Sea urchin gametes, embryos and larvae have also been used for fast, low-cost and reliable screening of toxic substances, and for detailed studies of their mechanism of action. One way to mitigate the commercial exploitation of wild echinoderm stocks is to develop laboratory culture methods to produce individuals for reseeding exploited populations and this is being done with sea urchins and sea cucumbers. However, releasing large numbers of captive-bred animals into the wild will undoubtedly affect the genetic composition of local populations, giving rise to important ethical issues related to the loss of a genetically unique wild stock. To aid conservation, it is necessary to improve the collection of data to quantify the extent of harvesting echinoderms and to document the location and catch data by species. It is also necessary to develop a global database of echinoderm species to summarise information on biology, ecology, threats, monitoring and conservation. Beyond increasing the number of echinoderm species to be protected, it is important to improve the conservation management of already protected species.
... Morfologi yang dimaksud, seperti bentuk cakram (disc) dan lengan, serta keberadaan atau ketiadaan ornamen tubuh (armor). Untuk mendapatkan perlindungan yang maksimal, bentuk ornamen (armor) tubuh dalam hal ini sangat berperan terutama pada area yang sering terpapar udara (Yamaguchi, 1975). Dalam penelitian ini bintang laut yang memiliki ornamen tubuh (duri) sangat berkembang adalah A. planci. ...
p>The objective of this study was to explore the information on the microhabitat preference of asteroidea in Hari Island Waters, Southeast Sulawesi. The specimens were collected in August 2012 and December 2012. The methods used in this study were road sampling technique, freehandpicking, and observation. The geographical coordinate position of the asteroidea and microhabitat were recorded by using GPS and then mapped by using the ArcGIS 10.1. Asteroidea map was overlayed with microhabitat map to determine the microhabitat preference. The study found 9 species of asteroidea belonging to 7 generas, 4 families, and 2 orders. All the asteroidea were relatively common species in the tropical shallow waters. The species were distributed along sides of the island with majority found in the northern side. The dominant species, Linckia laevigata , was found in all microhabitat which had beed adapted to various microhabitat conditions and water fluctuation. Based on area of distribution and population density, seastar tended to use reef coral as its microhabitat preference since reef coral could serve as a food source and habitat protection.
Keywords: Seastar, microhabitat preference, Hari island</p
... A total of 60 species of sea stars have been found from the Sunda Shelf region of Indonesia (Aziz & Janjoux, 1984), where 19 species of asteroid sea stars were recorded around Pulau Bodgaya and Pulau Sipadan, Sabah, Malaysia (George & George, 1987). There appears to be little endemism among asteroids on oceanic islands of this region (Marsh, 1974;Yamaguchi, 1975), and this could be due to good larval dispersal and consequent lack of geographical isolation. ...
... Unlike coral eggs, which are heavily preyed on by planktivorous fishes (e.g., Pratchett et al. 2001), Acanthaster spp. gametes and larvae are often avoided by planktivorous fishes and invertebrates (Yamaguchi 1974(Yamaguchi , 1975. Chemical analyses by Lucas et al. (1979) showed that eggs and larvae of Acanthaster spp. ...
... Prior to settlement, released gametes, swimming larvae, and late brachiolaria searching for suitable settlement substrates must avoid predation. Unlike coral eggs, which are heavily preyed upon by planktivorous fishes, A. planci gametes and larvae are often avoided upon visual recognition or rejected after tasting by fish and invertebrate predators (Yamaguchi, 1974(Yamaguchi, , 1975. Laboratory experiments by Lucas et al. (1979) showed that eggs and larvae contain saponins, which act as chemical defenses detected by and unpalatable to planktivorous fish. ...
Echinoderms are widely distributed in marine environments, from the coastal shore to the deep ocean. Underwater caves are an environment with very scarce information, especially about echinoderms. In the world only two echinoderm troglobites (limited to live inside of caves) species are known, the starfish Copidaster cavernicola (Mexican Caribbean) and the brittle star Amphicutis stygobita (Bahamas). Worldwide, the El Aerolito system (Cozumel, Mexico), is the marine cave with the highest species richness (25) of echinoderms (Asteroidea, Echinoidea, Holothuroidea and Ophiuroidea). In this study, for first time in an underwater cave was realized a quantitative ecological base line with the aim of knowing the density and dominance of the species. Echinoderms represented the dominant group with 65% of total abundance of the benthonic macro invertebrates, with a density up to 18 org/m2. This information is antagonist with the rest of the caves, since the crustaceans are the dominant fauna with 90% of the species. The dominant species in El Aerolito is the brittle star Ophionereis cf. reticulata with an average of 45.4 org/10m2, follow by Ophiomusium testudo (1.4org/10m2) and Asterina cf. pompom (0.2org/10m2). Also the sea urchin Eucidaris tribuloides, often referred to as exclusively marine, was found inhabiting at El Aerolito system living both in marine and brackish water, where it was very uncommon. This information, with continuous monitoring will allow knowing the health status of this invaluable ecosystem, to bookmarking foundations for conservation. Furthermore a bibliographic review of the echinoderms inhabiting underwater caves in the world is presented.
... Unlike coral eggs, which are heavily preyed on by planktivorous fishes (e.g., Pratchett et al. 2001), Acanthaster spp. gametes and larvae are often avoided by planktivorous fishes and invertebrates (Yamaguchi 1974(Yamaguchi , 1975. Chemical analyses by Lucas et al. (1979) showed that eggs and larvae of Acanthaster spp. ...
Outbreaks of crown-of-thorns starfish (Acanthaster spp.) remain a major cause of coral mortality in the Indo-Pacific, contributing to widespread and accelerating degradation of coral reef environments. This review examines the evidence for and against the principal hypotheses put forward to explain spatial and temporal patterns of outbreaks and also explores whether it is possible or feasible to intervene and limit ongoing degradation caused by crown-of-thorns starfish. The inherent biological characteristics of Acanthaster spp., such as exceptional fecundity, early maturation, and extreme flexibility in resource use, clearly contribute to extreme fluctuations in their abundance. Of the many hypotheses put forward to explain the occurrence of outbreaks, none has universal or unequivocal support. Clearly, however, the high incidence and severity of outbreaks at many reef locations cannot be sustained because anthropogenic changes to marine environments either have caused fundamental shifts in the population dynamics of Acanthaster spp. or have undermined the capacity of reef ecosystems to withstand these periodic disturbances. Reducing the incidence or severity of outbreaks of Acanthaster spp. is critical for reversing widespread and protracted declines in coral cover throughout the Indo-Pacific. Improved efficiency of direct controls provides opportunities to limit the progression and spread of outbreaks if detected early, but effective management of Acanthaster spp. really depends on definitive knowledge and appropriate action to address the ultimate causes of outbreaks. There are considerable, but not insurmountable, challenges to addressing important and persistent knowledge gaps relating to the biology of Acanthaster spp. This research is fundamental to ensure the persistence of coral reef ecosystems, especially given other emerging threats associated with global climate change.
... Prior to settlement, released gametes, swimming larvae, and late brachiolaria searching for suitable settlement substrates must avoid predation. Unlike coral eggs, which are heavily preyed upon by planktivorous fishes, A. planci gametes and larvae are often avoided upon visual recognition or rejected after tasting by fish and invertebrate predators (Yamaguchi, 1974(Yamaguchi, , 1975. Laboratory experiments by Lucas et al. (1979) showed that eggs and larvae contain saponins, which act as chemical defenses detected by and unpalatable to planktivorous fish. ...
The corallivorous crown-of-thorns starfish (Acanthaster planci) is perhaps one of most well known echinoderms on coral reefs, notorious for episodic population explosions and coral consumption on such unprecedented scales with major consequences to community structure. Outbreaks of A. planci, represent one of the most significant biological disturbances on coral reefs and remain one of the principal causes of widespread decline in live coral cover in Indo-Pacific reefs. At several locations, the effects of severe outbreaks on reef-building corals have been far greater than combined effects of all other major disturbances, including climate-induced coral bleaching. Increasing frequency and intensity of outbreak episodes have resulted in progressively slower recovery, which consequently degrades the integrity of reef ecosystems. Despite previous and ongoing efforts to control A. planci populations, outbreaks continue to pose serious reef management challenges. Longterm or permanent solutions depend on understanding the different biological and ecological aspects of the life history of A. planci to establish key limitations in recruitment and population replenishment. Outbreaks are manifestations of inherent instability within certain systems, attributed to either unique life history features (e.g., high fecundity, short generation times, high mortality during their early life history, and generalised patterns of prey and habitat use) which predispose A. planci to major fluctuations in population size, or major changes in the physical and biological environment that release populations from usual regulating factors. The three most prominent hypotheses put forward to explain outbreaks of A. planci all involve natural variation and constraints on the reproductive biology and early life history. The 'natural causes hypothesis' is based on the assumption that population sizes of highly fecund organisms with planktotrophic larvae, such as A. planci, are inherently unstable. The 'predator removal hypothesi' suggests that A. planci populations are normally regulated by high rates of predation on post-settlement juvenile starfish and that outbreaks arise as a consequence of the release from predation pressure due to overharvesting of predators. The 'larval starvation hypothesis' suggests that terrestrial runoff due to heavy rainfall causes elevated nutrient levels and lead to phytoplankton blooms, which provides nutrition for otherwise starved A. planci larvae. These hypotheses are not always mutually exclusive and will most likely vary spatially and temporally. This chapter reviews the unique features of A. planci reproductive biology and early life history that make it predisposed to population fluctuations and discuss factors that regulate gametogenesis, fecundity, spawning, fertilisation, larval development, and post settlement survival. These stages of the life cycle of A. planci are subject to stochastic processes involving food availability, predation, disease, settlement and spawning cues, dispersal, and environmental factors. Understanding the collective response of A. planci to this array of factors is essential in developing strategies to manage A. planci populations and reverse sustained declines in coral cover.
... Prior to settlement, released gametes, swimming larvae, and late brachiolaria searching for suitable settlement substrates must avoid predation. Unlike coral eggs, which are heavily preyed upon by planktivorous fishes, A. planci gametes and larvae are often avoided upon visual recognition or rejected after tasting by fish and invertebrate predators (Yamaguchi, 1974(Yamaguchi, , 1975. Laboratory experiments by Lucas et al. (1979) showed that eggs and larvae contain saponins, which act as chemical defenses detected by and unpalatable to planktivorous fish. ...
The rapid increase of marine trade and shipping imply that we are now capable of moving more organisms around the world in one month, than we used to in one century. The consequences of these marine introductions to new geographic areas not only are wide, ranging from environmental and ecosystem impacts (e.g., changes observed in the ecosystem functioning and loss of native biodiversity); to economic (e.g., damage caused to infrastructure such as fouling of pipes, etc.); and public health impacts (e.g., introduction of pathogens), as are a global issue. This review summarizes the importance of echinoderms as nonindigenous species (NIS). Past echinoderm introductions are revised. Accidental dispersal pathways by humans are identified and vectors and mechanisms of introductions are characterized in terms of relevance for echinoderm species. It is largely known that NIS not only are a cause by itself of biodiversity loss but also interact with biodiversity as a modifier factor for habitat destruction, compromising the integrity of marine ecosystems. The total number of NIS echinoderm around the globe are about 15 species, and despite the majority of these species cannot tolerate marked changes in salinity, temperature and light intensity, they can aggregate into colonies with significant densities causing bio-erosion in the surrounding habitat. Moreover, some of the economic impacts are huge and well known, such as the introduction of Asteria rubens in Turkey, where it become a voracious predator of the marketable mussel Mytilus edulis. This review outlines the current global known nonindigenous echinoderms, their potential impacts on marine environment and associated entry vector.
... We consider chemical defense as the most likely explanation for high survivorship of echinoderm larvae . Saponin compounds occur in starfish larvae, where they reduce predation by planktivorous fishes (Yamaguchi, 1975; Lucas et al., 1979 ). Although saponins have not been reported in echinoid larvae or embryos, they are known to occur in adult sea urchins (Mackie et al., 1977). ...
... planci in the ocean. In the laboratory, a number of predators have been demonstrated to take the larvae, including corals (Ormond et al. 1973;Yamaguchi 1973) and fish (Lucas 1975), but it has also been demonstrated that a number of fish species avoid or actively expel larvae (Yamaguchi 1974(Yamaguchi , 1975. Later studies by Lucas (1975) and Lucas et al. (1979) showed that the toxic compounds present in the larvae caused fish to discriminate against them. ...
A number of authors have hypothesized that outbreaks of the crown-of-thorns starfish (Acanthaster planci) are initiated by increased larval survival. This is then linked to the presence, in the water column, of various components of terrestrial runoff (pesticides, lowered salinity, nutrients, and dissolved and particulate organic matter) during the pelagic larval stage of the starfish. A related hypothesis suggests that recent outbreaks on the Great Barrier Reef (GBR) are initiated by the eutrophic condition of the GBR lagoon. It is claimed that this eutrophication is caused by anthropogenic input of terrestrially derived nutrients.
The present paper reviews current knowledge of the possible influence of components of terrestrial runoff on various stages in the life cycle of larval and juvenile A. planci. Processes that could be most influenced by enhanced nutrient conditions are those of planktonic survival, settlement success and juvenile survival. Available data on the state of eutrophication of parts of the GBR lagoon do not support assertions of general eutrophication but do suggest that elevated nutrient conditions exist in localized areas and that this may be caused by terrestrial runoff. The areas affected coincide with areas suggested as the primary initiation areas of two waves of crown-of-thorns outbreaks.
Further research required to understand larval survival includes studies on differences in the kinds and amounts of food available to A. planci larvae in low- and high-nutrient conditions, the effects of elevated nutrients on coralline algae and their associated bacteria and hence larval settlement processes, and the offshore effects of river-borne nutrients in coral reef regions.
New records of the Indo-Pacific seastar Mithrodia clavigera (Lamarck, 1816) include the north-central Gulf of Mexico, southeastern Florida, and Ascension Island. Material includes in-situ photographs, specimens from our own field collections, and museum specimens. This species was previously reported in the Atlantic basin in the 1880s off Brazil and in the western Caribbean Sea in the late 1960s and early 1970s. More recent findings are attributable to the advent of SCUBA, seafloor photography, and genetic analysis. The presence of M. clavigera in the Atlantic Ocean and adjacent waters probably represents a former connection with populations in the eastern Pacific Ocean before the rise of the Isthmus of Panama. Our observations here of specimens collected off Palm Beach and Fort Lauderdale, Florida, and the Gulf of Mexico add to our understanding of this species' behavior and ecology.
The biodiversity of coral reefs is dominated by invertebrates. Many of these invertebrates live in close association with scleractinian corals, relying on corals for food, habitat or settlement cues. Given their strong dependence on corals, it is of great concern that our knowledge of coralassociated invertebrates is so limited, especially in light of severe and ongoing degradation of coral reef habitats and the potential for species extinctions. This review examines the taxonomic extent of coral-associated invertebrates, the levels of dependence on coral hosts, the nature of associations between invertebrates and corals, and the factors that threaten coral-associated invertebrates now and in the future. There are at least 860 invertebrate species that have been described as coral associated, of which 310 are decapod crustaceans. Over half of coral-associated invertebrates appear to have an obligate dependence on live corals. Many exhibit a high degree of preference for one or two coral species, with species in the genera Pocillopora, Acropora and Stylophora commonly preferred. This level of habitat specialization may place coral-associated invertebrates at a great risk of extinction, particularly because preferred coral genera are those most susceptible to coral bleaching and mortality. In turn, many corals are also reliant on the services of particular invertebrates, leading to strong feedbacks between abundance of corals and their associated invertebrates. The loss of even a few preferred coral taxa could lead to a substantial decline in invertebrate biodiversity and have far-reaching effects on coral reef ecosystem function. A full appreciation of the consequences of further coral reef degradation for invertebrate biodiversity awaits a more complete description of the diversity of coral-associated invertebrates, the roles they play in coral reef ecosystems, their contribution to reef resilience and their conservation needs. © R. N. Gibson, R. J. A. Atkinson, J. D. M. Gordon, I. P. Smith and D. J. Hughes, Editors Taylor & Francis. All rights reserved.
Current models to explain ‘primary outbreaks’ of Acanthaster planci assume recruitment of larvae to the natal reef. In the light of recent studies and the current awareness of the importance of larval advection in the recruitment of coral reef organisms, two new models are offered; particular attention is drawn to the possible importance of persistent breeding populations of A. planci as sources of larvae initiating sequences of secondary outbreaks. Reef habitats harbouring stable A. planci populations are characterised by hydrodynamic systems retentive to larvae, and poor coral prey availability, in contrast to the strong flushing and rich coral cover of open-water reefs where outbreaks occur. Other features of stable A. planci populations are a significant contribution to diet by alternatives to hard corals; and reduced predator pressure. A simple model of the important processes influencing starfish population stability is developed. The ability to alternate between endemic and epidemic life-styles in different habitats is a common feature of ‘outbreaking’ organisms.
The genus Heliaster (Gray, 1840) includes a remarkable group of seven species that inhabit rocky intertidal and shallow subtidal habitats and are morphologically characterized by a large disc and a large number of rays. Geographically, the genus is restricted along the tropical, subtropical, and temperate coasts of the Eastern Pacific. Four species inhabit mainland littoral sites: Heliaster helianthus (Lamarck, 1816) in the tropical, subtropical and temperate west coasts of South America; Heliaster polybranchius H. L. CLARK, 1907, in the tropical coast of Peru; Heliaster kubiniji XANTUS, 1860 and Heliaster microbrachius Xantus, 1860, in the west coasts of Mexico and central America. Three species inhabit off shore archipelagos: Heliaster canopus Perrier, 1875, in Chile's Juan Fernández Archipelago; and Heliaster solaris A. H. Clark, 1920, and Heliaster cumingii (Gray, 1840) in the Galápagos Archipelago of Ecuador (see J. E. Gray 1840, H. L. Clark 1907, A. H. Clark 1920, A. M. Clark and Mah 2001). © 2013 The Johns Hopkins University Press. All rights reserved.
This review provides a brief update of the occurrence and adaptive significance of asexual reproduction in echinoderms. It then focuses on the state of knowledge of biotic and abiotic factors that influence asexual processes in this group, particularly factors that may play a role in regulating the expression and relative proportion of asexual versus sexual phenotypes within populations of species, as well as factors modulating and triggering asexual processes. The information presented in the review is synthesized into the form of a basic model depicting how environmental factors may interact with physiological factors to regulate asexual reproduction in echinoderms, and to show how such regulatory processes may parallel in some ways those known to regulate sexual reproduction. Since the model is based mainly on correlational evidence derived from comparative field observations, a number of experimental approaches for testing the predictions of the model are discussed briefly.
An asteroid fauna is described from the Albian (Cretaceous) interval of the Washita Group of central Texas. New genera and species are Alkaidia sumralli , (Benthopectinidae), Capellia mauricei (Goniasteridae), and Betelgeusia reidi (Radiasteridae). Additional new genera are Fomalhautia (Goniasteridae), and Denebia and Altairia (Ophidiasteridae). Crateraster texensis (Goniasteridae), new combination, is similar to the European type species, C. quinqueloba. An unnamed species of Crateraster and an unassigned goniasterid are also present. All Washita genera are extinct, but all belong to extant families. The fauna is largely distinct from that of the somewhat younger European Cretaceous chalk.
The Radiasteridae (e.g., Betelgeusia ) is inferred to hold a basal position in the Paxillosida; Betelgeusia extends the range of the family back to the Cretaceous, closer to the diversification of the living asteroid orders. Asteroids capable of burying themselves in sediment (and only self-buriers) share some form of channelization for the passage of water currents between the primary ossicles of the body surface. Channels in Betelgeusia indicate semi-infaunal habits similar to those of living Astropecten and Luidia. Betelgeusia represents the third semi-infaunal paxillosidan family now known from the Cretaceous, although none are known from older rocks, suggesting a broadening of the asteroid adaptive zone during the Cretaceous. The Goniasteridae, Radiasteridae, and Benthopectinidae are less important in shelf settings today than they appear to have been during Washita deposition, whereas the Astropectinidae, Luidiidae, and the Echinasteridae are absent from the Washita although they are common today in similar settings.
The biodiversity of coral reefs is dominated by invertebrates. Many of these invertebrates live in close association with scleractinian corals, relying on corals for food, habitat or settlement cues. Given their strong dependence on corals, it is of great concern that our knowledge of coral-associated invertebrates is so limited, especially in light of severe and ongoing degradation of coral reef habitats and the potential for species extinctions. This review examines the taxonomic extent of coral-associated invertebrates, the levels of dependence on coral hosts, the nature of associations between invertebrates and corals, and the factors that threaten coral-associated invertebrates now and in the future. There are at least 860 invertebrate species that have been described as coral associated , of which 310 are decapod crustaceans. over half of coral-associated invertebrates appear to have an obligate dependence on live corals. Many exhibit a high degree of preference for one or two coral species, with species in the genera Pocillopora, Acropora and Stylophora commonly preferred. This level of habitat specialization may place coral-associated invertebrates at a great risk of extinction, particularly because preferred coral genera are those most susceptible to coral bleaching and mortality. In turn, many corals are also reliant on the services of particular invertebrates, leading to strong feedbacks between abundance of corals and their associated invertebrates. The loss of even a few preferred coral taxa could lead to a substantial decline in invertebrate biodiversity and have far-reaching effects on coral reef ecosystem function. A full appreciation of the consequences of further coral reef degradation for invertebrate biodiversity awaits a more complete description of the diversity of coral-associated invertebrates, the roles they play in coral reef ecosystems, their contribution to reef resilience and their conservation needs.
Among the most fascinating animals in the world's oceans are the more than 2,000 species of starfish. Called "Asteroids" by scientists who study them (after their taxonomic name, Asteroidea)-or sea stars in some parts of the world-starfish are easily recognized because of their star-like form. Starfish is a comprehensive volume devoted to the integrative and comparative biology and ecology of starfish. Written by the world's leading experts on starfish, the integrative section covers topics such as reproduction, developmental biology and ecology, larval ecology, and the ecological role of starfish as a group. The comparative section considers the biology and ecology of important species such as Acanthaster planci, Heliaster helianthoides, Asterias amurensis, and Pisaster ochraceus. Replete with detailed, scientifically accurate illustrations and the latest research findings, Starfish examines the important role of these invertebrates in the marine environment, a topic of great interest because of their impact on the food web. As major predators that are able to evert their stomach and wrap it around their prey, starfish can have a significant impact on commercial fisheries. Starfish are of interest not only to echinoderm specialists but also to marine biologists and invertebrate zoologists in general and, increasingly, to the medical community. A starfish's ability to regenerate body parts is almost unequalled in the animal world, making them ideal models for basic science studies on the topic. Contributors: Charles D. Amsler, Bill J. Baker, Mario Barahona, Michael F. Barker, Maria Byrne, Juan Carlos Castilla, Katharina Fabricius, Patrick Flammang, Andrew S. Gale, Carlos F. Gaymer, Jean-François Hamel, Elise Hennebert, John H. Himmelman, Michel Jangoux, John M. Lawrence, Tatiana Manzur, James B. McClintock, Bruce A. Menge, Annie Mercier, Anna Metaxas, Sergio A. Navarette, Timothy D. O'Hara, John S. Pearse, Carlos Robles, Eric Sanford, Robert E. Scheibling, Richard L. Turner, Carlos Renato R. Ventura, Kristina M. Wasson, Stephen A. Watts. © 2013 The Johns Hopkins University Press. All rights reserved.
In contrast with what has been reported for a Japanese sea star, the oocytes of Asterias rubens contain high levels of asterosaponins at the time of spawning.
Micronesia is an island nation located north of Papua New Guinea in the Pacific Ocean. A survey was conducted on Chuuk, which is one of the four main islands of Micronesia, from 11-25 Nov 2012. Echinoderms collected at one intertidal area as well as at 16 SCUBA diving points of 10-40 m depths in the subtidal zone were identified based on morphological characteristics. In total, 35 species from 165 individuals were identified: two crinoids, eight asteroids, four ophiuroids, seven echinoids, and 14 holothuroids. Among them, one asteroid, one ophiuroid, one echinoid, and two holothuroids were newly recorded from Micronesia.
Shallow-water sea stars of the Bay of Nhatrang (Southern Vietnam) and their obligatory macrosymbionts are studied. A total of 39 sea star species of 13 families are recorded; 19 of them are new for the Vietnamese fauna. More than half of species (61.6%) belong to the families Oreasteridae and Ophidiasteridae. The fauna of obligatory macrosymbionts of sea stars of the Bay of Nhatrang includes 21 species (including one sedentary ctenophoran, five polychaetes, four mollusks, two shrimps, eight copepods, and one fish), 18 of which are recorded in Vietnam for the first time. The taxonomic composition of sea stars and fauna of their symbionts have shown a high species diversity of these groups in the Bay of Nhatrang compared to other regions.
1. Asterosaponins, detergents from sea stars, stimulate germinal vesicle breakdown (GVB) in oocytes of the zebrafish Brachydanio rerio.2. It is likely that this stimulation is not due to the surface-tension lowering property of the saponins or to some specific part of the molecule.3. The effect of asterosaponins on GVB resembles that of several steroids with a progesterone or corticosteroid-like structure. However, on treatment with asterosaponins oocytes show a strongly decreased c-AMP level, even 3 hr after termination of the treatment, whereas on treatment with steroids this decrease is only a transient phenomenon. It is therefore supposed that asterosaponins irreversibly alter the oocyte membrane by interacting with the cholesterol molecules in it.4. Liposomes containing only lecithin strongly stimulate GVB; the addition of small amounts of cholesterol to the liposomes suppresses GVB, whereas the addition of higher amounts of cholesterol seems to stimulate GVB.5. The significance of these findings is discussed.
Settlement trials conducted with larvae of Acanthaster planci revealed a moderate degree of substratum specificity. Highest rates of settlement and metamorphosis occurred on coral rubble and the crustose coralline alga Lithothamnium pseudosorum, but rates were more variable on the coralline. Treatment of highly inductive shards of L. pseudosorum with antibiotics reduced their inductive activity to low levels, suggesting that induction of settlement and metamorphosis of A. planci by L. pseudosorum may be mediated by epiphytic bacteria. Larvae always settled on sections of thallus having high densities of bacteria, but never on adjacent areas where epiphytic bacteria were sparse. The inductive stimulus is likely to be chemical. The spatial distribution of coral rubble and L. pseudosorum on and around Great Barrier Reef midshelf reefs, the location of hydrodynamic retention cells around reefs, and the pattern of outbreaks on the GBR, suggest that mass settlements of A. planci are more likely to occur in deep than in shallow water. This would explain the paradox that outbreaks of A. planci on the GBR are not heralded by increases in abundances of juveniles in shallow water, but are first observed as adult starfish ascending from deepwater. -from Authors
Lecithotrophic echinoderm eggs and larvae are likely to possess deterrents to predation because they are large, lack behavioral defenses, and are often conspicuously colored. We performed laboratory feeding assays to test deterrence in multiple developmental stages of common shallow-water lecithotrophic asteroids and holothuroids in the San Juan Islands, Washington (seven asteroids, five holothuroids) to five functionally diverse, potentially sympatric predators (sculpins, shrimp, ascidians, and two species of anemones). At least one developmental stage of most echinoderm species tested deterred at least one predator (causing food rejection). Using sculpins as predators, the hypothesis that deterrence varied among developmental stages of a species was rejected for the four echinoderm species in which older embryos were tested. Different predator species often responded differently to the same developmental stage. Compared to the invertebrate predators, sculpins were usually the most sensitive assay predator. The present results provide additional support for the hypothesis that lecithotrophic eggs and larvae are deterrent, and in this study the deterrents persisted through early life stages. Because these stages lack obvious structural or behavioral defenses, the most likely source of their deterrence is chemical.
Several traits were examined in four potential coral prey species (colony form, organic matter content, caloric density, tissue accessibility, mucus release, cnidocyst composition, toxicity, and colony defense by crustacean coral guards) to help understand the feeding preference of the Hawaiian asteroid corallivore Culcita novaeguineae Muller & Troschel. In laboratory experiments, C. novaeguineae exhibits a preference for Pocillopora damicornis (L.) and Pocillopora meandrina Dana over Porites compressa Dana, Montipora verrucosa (Lamarck) and Fungia scutaria (Lamarck). The feeding rate of Culcita novaeguineae on Pocillopora damicornis was ≈ 28 cm2or 250 cm3 per day. In limited field observations, a preference was shown by Culcita novaeguineae for small colonies of Pocillopora meandrina which were totally killed (all tissues removed from branches) after attack by the sea star. Although the organic matter content (mg dry wt/cm3) of Pocillopora was the lowest of the four corals, the percent loss of organic matter after feeding (“utilization” by Culcita) was the highest. This high intake of organic matter corresponds with the superficial location of the tissue layers and the ease of removal of tissues (by “water piking”) in Pocillopora compared with the other corals. Small colonies of Pocillopora are eaten more frequently than large colonies; the former harbor relatively low numbers of crustacean guards (crabs and shrimp) and their guards are small compared with large colonies. Coral mortality caused by Culcita ( 1.0 m2/yr) is only about one-fifth of that by Acanthaster (5.3 m2/yr), but the selective feeding of Culcita on Pocillopora, and its avoidance of nonpocilloporid corals, could affect significantly the relative abundance of corals in Hawaiian reef assemblages.
The asteroid Linckia multifora (Lamarck) reproduces by autotomy of arms. Seven phases are recognized in its asexual reproductive cycle (autotomized arms; comets; counter-comets; post counter-comet I, II and III; and disc-parents). Individuals of the comet phase represent the highest percentage for population samples collected throughout the year from several sites on Guam, indicating a continuous asexual reproduction through which populations of L. multifora are being maintained.
The suggestion that saponins in eggs and larvae of Acanthaster planci (L.) serve as chemical defences was tested by feeding groups of planktivorous pomacentrid fish with random series of gelatin food particles, some with and some without crude saponin extract from A. planci. The four fish species discriminated at statistically significant levels against food particles with crude saponin extract at 1× 10−3 and 1× 10−5 parts of wet weight. Three species also discriminated at significant levels against particles with 1× 10−7 parts crude saponin extract per wet weight. Degree of discrimination was strongly influenced by the state of hunger of the fish. Tastiness of particles containing saponins also influenced acceptability. The lower two concentrations of saponins used in these feeding trials were respectively two and four magnitudes less than in A. planci eggs and larvae. Thus, the saponins in eggs and larvae of A. planci are at levels detectable by, and unpalatable to, planktivorous fish and they account, at least in part, for the observed rejection of these early developmental stages by planktivorous fish.
A survey was made of the structure and ecology of the reefs of Saipan and the probable effects of the crown-of-thorns starfish Acanthaster planci on the present status of the coral communities. The geomorphology of the nearshore platform is briefly discussed, and a glossary applies coral reef terminology to the Saipan reefs. Acanthaster predation is examined as a possible regulating factor in reef community structure. The marked preference of Acanthaster for some species of corals (Acropora, Montipora spp.) and its avoidance of others (Synarea iwayamensis, Pocillopora eydouxi) is of considerable ecological significance because of its selective effect on population structure of coral reefs subject to different levels of predation. The discussion gives information on population, behaviour, and feeding of the starfish; on the relation between their infestations and damage to reefs from various causes (human agencies, storms); and on the predation of reef corals by the cushion starfish Culcita novaeguineae. An unusually abundant living fauna of hermatypic sponges of geological significance was discovered during this survey.
The feeding behaviour of eight species of medusae was studied; total food consumed, rates of digestion, and growth rate were noted, especially in Cyanea and Aurelia.Aurelia up to 5 cm diam can accept a wide range of size of food organisms obtained by filtering sea water through the curtain of tentacles during pulsation, whereas most other species find their food by random contact with the tentacles. In Bougainvillia it is the dichotomously branched oral tentacles that capture the food. The apparent selectivity of Sarsia in feeding on copepods is shown to be a physical effect produced by its method of swimming. Leuckartiara can catch and eat active organisms larger than itself. None of the medusae examined showed any reaction to artificial stimulation by a vibrating probe.The method of transfer of food from the tentacles to the mouth is closely associated with the structure of the medusa. Long trailing tentacles contract and lift food towards the mouth and if the manubrium is long it can be manipulated to pick off the food from the tentacles. If the tentacles are short the umbrella edge folds inwards towards the mouth. If there is no manubrium, as in Staurophora, the cruciform stomach can accept food at any point.Larval fish are important in the diet of most medusae and rough estimates are given of a probable consumption of 50–250 larval fish per hydromedusa, about 450–500 by each Aurelia, and in the order of 15,000 by Cyanea. A conversion factor is given for food eaten by medusae of 37%, though this is based on only few data.Following the work of Horridge and Boulton (Proc. Roy. Soc. (Ser. B) 168: 413–419, 1967), who found that Spadella could be artificially stimulated to bite vibrating probes, similar experiments were made with Sagitta elegans. Although the chaetognaths were successfully kept alive the probes produced no feeding reaction. The methods are outlined for the benefit of others wishing to continue such investigations.
1. The development of new cultivation devices, the double kuvette and the phytoplanktonkreisel, made it possible to culture the 4 species of ctenophores occurring in the southern North Sea:Pleurobrachia pileus, Bolinopsis infundibulum, Beroe cucumis andBeroe gracilis. These ctenophores are holoplanktonic organisms of great ecological importance in local marine food chains.
2. The double kuvette, an improved version of the planktonkreisel permits the control of growth and feeding rate without disturbing the test organisms.
3. The phytoplanktonkreisel permits experiments close to habitat conditions with high seston densities and wave action.
4.Beroe gracilis andPleurobrachia pileus could be reared from egg to egg; the other 2 species could be maintained over several weeks.
5. Data are given on the nutrition of all 4 species as well as on their growth rates, development and behavior.
6.Beroe gracilis feed exclusively onPleurobrachia pileus; Beroe cucumis feed mainly onBolinopsis infundibulum.
7. The young stages only ofBolinopsis infundibulum have true larval organs (tentacles) and may be called larvae.
8. Some ecological implications of the findings are discussed.
Thesis (M. Sc.)--University of Hawaii. Includes bibliographical references.
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