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Background The Red Sea contains thousands of kilometers of fringing reef systems inhabited by clownfish and sea anemones, yet there is no consensus regarding the diversity of host anemone species that inhabit this region. We sought to clarify a historical record and recent literature sources that disagree on the diversity of host anemone species in the Red Sea, which contains one endemic anemonefish, Amphiprion bicinctus Rüppell 1830. Results We conducted 73 surveys spanning ~ 1600 km of coastline from the northern Saudi Arabian Red Sea to the Gulf of Aden and encountered seven species of host anemones, six of which hosted A. bicinctus. We revise the list of symbionts for A. bicinctus to include Stichodactyla haddoni (Saville-Kent, 1893) and Stichodactyla mertensii Brandt, 1835 which were both observed in multiple regions. We describe Red Sea phenotypic variability in Heteractis crispa (Hemprich & Ehrenberg in Ehrenberg, 1834) and Heteractis aurora (Quoy & Gaimard, 1833), which may indicate that these species hybridize in this region. We did not encounter Stichodactyla gigantea (Forsskål, 1775), although the Red Sea is the type locality for this species. Further, a thorough review of peer-reviewed literature, occurrence records, and misidentified basis of record reports dating back to the early twentieth century indicate that it is unlikely that S. gigantea occurs in the Red Sea. Conclusions In sum, we present a new guide for the host anemones of the Red Sea, revise the host specificity of A. bicinctus, and question whether S. gigantea occurs in the central and western Indian Ocean.

International audience; Determining how plasticity of developmental traits responds to environmental conditions is a challenge that must combine evolutionary sciences, ecology, and developmental biology. During metamorphosis, fish alter their morphology and color pattern according to environmental cues. We observed that juvenile clownfish ( Amphiprion percula ) modulate the developmental timing of their adult white bar formation during metamorphosis depending on the sea anemone species in which they are recruited. We observed an earlier formation of white bars when clownfish developed with Stichodactyla gigantea ( Sg ) than with Heteractis magnifica ( Hm ). As these bars, composed of iridophores, form during metamorphosis, we hypothesized that timing of their development may be thyroid hormone (TH) dependent. We treated clownfish larvae with TH and found that white bars developed earlier than in control fish. We further observed higher TH levels, associated with rapid white bar formation, in juveniles recruited in Sg than in Hm , explaining the faster white bar formation. Transcriptomic analysis of Sg recruits revealed higher expression of duox , a dual oxidase implicated in TH production as compared to Hm recruits. Finally, we showed that duox is an essential regulator of iridophore pattern timing in zebrafish. Taken together, our results suggest that TH controls the timing of adult color pattern formation and that shifts in duox expression and TH levels are associated with ecological differences resulting in divergent ontogenetic trajectories in color pattern development.

Relatively few studies have investigated the genetic population structure of sea anemones. This is particularly true for sea anemones that host some of the most iconic fishes on coral reefs, the anemonefishes. One of the main reasons for this knowledge gap is the lack of appropriate genetic markers. We developed and characterized a total of 47 novel polymorphic microsatellite markers for four host sea anemone species from the Indo-Pacific: Entacmaea quadricolor (n = 16 microsatellite markers), Heteractis magnifica (n = 8), Stichodactyla mertensii (n = 13), and Stichodactyla gigantea (n = 10). Here, we report genetic diversity statistics from two different sampling locations for each anemone species. Overall, we found that most markers were highly polymorphic. On average, we found a mean of seven alleles per locus. Observed and expected heterozygosities displayed high variation among loci, ranging from 0.033 to 0.980 and from 0.038 to 0.927, respectively. Only four loci showed deviations of Hardy–Weinberg equilibrium in both populations and were identified as having null alleles. Additionally, two pairs of loci were identified to be in linkage disequilibrium in only one population. Host anemones are highly sought after in the marine aquarium trade and are susceptible to thermal bleaching. Although most studies focus on their obligate symbionts (the anemonefish), genetic analyses of host sea anemones can expand our understanding of the biology, connectivity, and population structure of these organisms and potentially help develop conservation strategies that will aid both the host and its symbionts.

International audience; The life-history traits and population dynamics of species are increasingly being attributed to the characteristics of their preferred habitats. While coral reef fish are often strongly associated with particular habitats, long-term studies establishing the demographic and life-history consequences of occupying different reef substrata are rare and no studies have monitored individuals in situ over their lifetime and determined the fate of their offspring. Here, we documented a quasi-turnover and local reproductive success for an entire population of orange clownfish (Amphiprion percula) from Kimbe Island, Papua New Guinea, by taking bi-annual samples of DNA over a 10-yr period (2003–2013). We compared demographic and life-history traits of individuals living on two host anemone species, Heteractis magnifica and Stichodactyla gigantea, including female size, adult continued presence (a proxy for relative longevity range), early post-settlement growth, the number of eggs per clutch and ‘local’ reproductive success (defined for each adult as the number of offspring returning to the natal population). Our results indicate that while the relative longevity of adults was similar on both host anemone species, females living in H. magnifica were larger than females in S. gigantea. However, despite females growing larger and producing more eggs on H. magnifica, we found that local reproductive success was significantly higher for clownfish living in S. gigantea. Life-history traits also exhibited local spatial variation, with higher local reproductive success recorded for adults living on S. gigantea on the eastern side of the island. Our findings support a ‘silver-spoon’ hypothesis that predicts individuals that are fortunate enough to recruit into good habitat and location will be rewarded with higher long-term reproductive success and will make a disproportionate contribution to population renewal.

We studied the ectosymbionts associating with the sea anemone Stichodactyla gigantea at Kosrae, Micronesia. Ectosymbionts of seven species associated with 60.7% of S. gigantea (n=28), with a mean of 2.4 per anemone and 3.9 per occupied anemone. Anemones hosting one or more ectosymbionts did not differ significantly in size from anemones lacking ectosymbionts and there was no significant correlation between anemone size and the number of ectosymbionts. Of 67 ectosymbionts observed, the sea cucumber Stichopus vastus comprised 23.9%, followed by the shrimp Thor amboinensis (20.9%), unidentified hermit crabs (Paguroidea; 20.9%), the cardinalfish Ostorhinchus novemfasciatus (20.9%), the shrimp Periclimenes brevicarpalis (9.0%), the sea cucumber Holothuria hilla (3.0%), and an unidentified brachyuran crab (1.5%). This study documents the first records of S. vastus, H. hilla, and O. novemfasciatus associating with S. gigantea, and the first locality records of S. gigantea, T. amboinensis, P. brevicarpalis, and S. vastus for Kosrae. Because humans often harvest S. gigantea for food at Kosrae, we recommend protecting the symbiotic assemblage of S. gigantea by establishing a sustainable system of harvesting.

The clown anemonefish ‘Nemo’ Amphiprion ocellaris is the most popular fish species in the global marine ornamental trade and also its host sea anemones Heteractis magnifica, Stichodactyla gigantea, and Stichodactyla mertensii are traded. However, total catch and the potential impact of exploitation of these target organisms in Spermonde Archipelago, Indonesia, are not known. Therefore, the main objective of this study was to investigate the impact of the fishery on populations of A. ocellaris and its host anemones and how management could be improved. In order to obtain a comprehensive view on the marine ornamental fishery and trade of these species in Spermonde, this study also investigated the socioeconomics of the marine ornamental fishery and the catch records for A. ocellaris and it's host anemones. The study revealed that both, A. ocellaris and sea anemone densities were significantly lower at coral reefs with high exploitation (HE) than at reefs with low exploitation (LE). The total body length and group size of A. ocellaris was also significantly smaller at HE than at HL sites. The yearly amount traded by middlemen is estimated to 140 000 specimens of A. ocellaris and 31 000 anemones. The socioeconomic analysis showed that educational level of marine fishermen family members was low; most of them only finished elementary school. The household income analysis showed that marine ornamental fishery was not the major source of income, covering 13−43% of the expenses, with the exception of one studied island (84%). These findings revealed a considerable negative impact of marine ornamental fishery on the target populations and therefore, the implications for management strategies and conservation are discussed, including fish size restrictions for collectors, marine protected areas and regular monitoring of the amount of trade at middlemen.

Cnidarians comprise an old and diverse animal phylum, and possess a wide variety of biologically active substances. Sea anemones contain a diversity of interesting biologically active compounds including some potent toxins. In the present work, the sea anemones Stichodactyla mertensii and Stichodactyla gigantea, collected from the Mandapam coast, are characterized biomedically and pharmacologically. The crude protein was obtained by using methanol and aqueous extracts. The respective protein contents of S. mertensii and S. gigantea were found to be 2.10 µg/mL and 1.87 µg/mL. The methanol and aqueous extracts of S. mertensii and S. gigantea yielded six and nine bands by SDS-PAGE on 12% gel. In the hemolytic assay, both extracts exhibited hemolytic effect on chicken, goat, cow and human erythrocytes ('A', 'B' and 'O'). The neurotoxic effects of these crude extracts were determined in vivo using the sea shore crab Ocypode macrocera and mortality was observed. The mouse bioassay for lethality was performed on male albino mice. The crude extract of S. mertensii showed higher lethality (58 seconds at 1 mL-dose) than that of S. gigantea (2 minutes and 10 seconds at 0.75 mL-dose). The analgesic activity test was also carried out on albino mice by Eddy's hot plate and tail-flick methods. The extracts showed moderate analgesic effect by both hot-plate and tail-flick methods. These characteristics emphasize the need for the isolation and molecular characterization of new active toxins in S. mertensii and S. gigantea.

Objective To investigate the antimicrobial activities of the methanol and aqueous extract of sea anemone Stichodactyla mertensii (S. mertensii) and Stichodactyla gigantea (S. gigantea) . Methods The sea anemone S. mertensii and S. gigantea were subjected to extraction by using methanol and distilled water. They were evaluated for antimicrobial activity against bacterial and fungal pathogens. Results In antibacterial activity, S. gigantea exhibited significantly inhibitory activity against Pseudomonas aeruginosa than the S. mertensii of butanolic extract. In antifungal activity, the S. mertensii extract showed good activity against Aspergillus niger ( A. niger ) compared with other strains. Whereas S. gigantea recorded maximum and minimum zone of inhibition against Botrytis cinerea, A. niger and Cladosporium cucumerinum respectively. Conclusions The results support that the sea anemones S. mertensii and S. gigantea extracts for treatment of some bacterial and fungal diseases as an ethanomedicinal source.

Sea anemones are a rich source of peptide toxins acting on ion channels. Two classes of peptide toxins, site-3 sodium channel toxins and Kv1 potassium channel toxins, have been well characterized and some of them used as valuable pharmacological reagents. Recently, the following six peptides toxins, which structurally constitute a new family but target different ion channels, have been isolated: BDS-I and -II (Kv3 potassium channel toxins) from Anemonia sulcata, APETx1 (human ether-a-go-go-related gene potassium channel toxin) and APETx2 (acid-sensing sodium channel toxin) from Anthopleura elegantissima, BcIV (sodium channel toxin) from Bunodosoma caissarum and Am II (whose target is unknown) from Antheopsis maculata. In addition, the following structurally novel peptide toxins have also emerged in sea anemones: gigantoxin I (epidermal growth factor-like toxin) from Stichodactyla gigantea and acrorhagins I and II from acrorhagi (specialized aggressive organs) of Actinia equina. This review deals with the structural and functional features of these recently isolated sea anemone peptide toxins that are promising tools in studying the physiology of diverse ion channels.

Habitat loss due to land reclamation often occurs in sandy coral reef shore zones. The giant sea anemone Stichodactyla gigantea, which harbors the false clown anemonefish Amphiprion ocellaris, both of which are potentially flagship species, inhabit these places. To assess habitat quality for S. gigantea, we examined correlative associations between the number and the body size of S. gigantea and the amount of habitat types in fine-scale seascape composition quantified from an enlarged section of a high-resolution (1/2,500) color aerial photograph of the shallow shore zone of Shiraho Reef, Ishigaki Island, Japan. This study confirmed that anemones were most abundant at the edges of dense seagrass beds characterized by shallow sandy bottoms, rock beds, and sparse seagrass beds, while they were less abundant in coral patch reefs. However, anemones inhabiting coral patch reefs were significantly larger and their rate of disappearance over 3 years was lower than those inhabiting other habitats. This suggests that coral patch reefs may be more suitable habitats supporting larger animals and greater persistence of S. gigantea. The visual census techniques applied here, combined with aerial photography and image-analysis software, may be useful as a simple analytical tool for local assessment of suitable habitats for relatively small-bodied marine fauna in shallow-water seascapes.

Chromoproteins (CPs) have unique colors and can be used in biological applications. In this work, a novel blue CP with a maximum absorption peak (λmax) at 608 nm was identified from the carpet anemone Stichodactyla gigantea (sgBP). In vivo expression of sgBP in zebrafish would change the appearance of the fishes to have a blue color, indicating the potential biomarker function. To enhance the color properties, the crystal structure of sgBP at 2.25 A resolution was determined to allow structure-based protein engineering. Among the mutations conducted in the Gln-Tyr-Gly chromophore and chromophore environment, a S157C mutation shifted the λmax to 604 nm with an extinction coefficient (e) of 58,029 M-1·cm-1 and darkened the blue color expression. The S157C mutation in the sgBP chromophore environment could affect the color expression by altering the deprotonation state of the phenolic group in the chromophore. Our results provide a structural basis for the blue color enhancement of the biomarker development.

When social groups monopolize discrete habitat patches, group size may be positively correlated with patch size. The correlation can be a direct consequence of limited resources. Alternatively, it can be an indirect consequence of patch-size effects on a dominant group member. We asked which of these two mechanisms was responsible for a positive correlation between the group size of false clown anemonefish (Amphiprion ocellaris Cuvier in Cuvier and Valenciennes, 1830) and that of the host sea anemone Stichodactyla gigantea (Forskål, 1775). We argue that some false clown anemonefish groups may have reached the carrying capacities of their hosts, but that the group size : patch size correlation in the population as a whole is best interpreted as an indirect consequence of a positive relationship between anemone size and the length of the dominant group member. The dominant's length in turn limits group size because dominant group members inhibit the growth of their subordinates. Thus, a correlation between group size and patch size need not imply resource limitation of subordinate group members.

Three peptide toxins (gigantoxins I–III) with crab toxicity were isolated from the sea anemone Stichodactyla gigantea by gel filtration on Sephadex G-50 and reverse-phase HPLC on TSKgel ODS-120T and their complete amino acid sequences were determined. Gigantoxins II (44 residues) and III (48 residues) have LD 50 (against crabs) of 70 and 120 μg/kg, respectively, and are analogous to the known type 1 and 2 sea anemone sodium channel toxins, respectively. On the other hand, gigantoxin I (48 residues) is potently paralytic to crabs (ED 50 215 μg/kg), although its lethality is very weak (LD 50 >1000 μg/kg). Interestingly, gigantoxin I has 31–33% homologies with mammalian epidermal growth factors (EGFs), with the same location of six cysteine residues. In accordance with the sequence similarity, gigantoxin I exhibits EGF activity as evidenced by rounding of A431 cells and tyrosine phosphorylation of the EGF receptor in the cells, although much less potently than human EGF. Gigantoxin I is the first example of EGF-like toxins of natural origin.

For reef fishes that do not move between habitat patches following settlement, habitat selection is expected during settlement. Although false clown anemonefish, Amphiprion ocellaris, are sedentary following settlement, they are not especially discriminating during settlement, and are commonly found occupying anemones at which no apparent nest site exists. In this study I report on mobility of Stichodactyla gigantea sea anemones, including anemones with resident false clowns. I argue that anemone mobility can help explain why settling false clowns are not more discriminating: although the per annum probability of an anemone moving is low, the probability of that anemone moving over the course of a resident's life is considerably higher. Therefore, an anemone's current microhabitat may not be a good predictor of its microhabitat and suitability as a host in the future.

Anemonefishes are habitat specialists that form obligate symbioses with host sea anemones (Fautin and Allen 1997). Some anemonefishes associate with a range of hosts, whereas others only use one host species. The wideband anemonefish Amphiprion latezonatus is endemic to high-latitude reefs in eastern Australian and, in published sources, has previously only been documented with Heteractis crispa (Fautin and Allen 1997; Ollerton et al. 2007). Here, we establish that A. latezonatus utilizes two additional species, Entacmaea quadricolor and Stichodactyla gigantea. In an unpublished thesis, Richardson (1996) recorded A. latezonatus associating with E. quadricolor in the Solitary Islands Marine Park, New South Wales (NSW), Australia. Sub-adults were found to occupy both H. crispa and E. quadricolor, while breeding pairs were found only in E. quadricolor (Richardson 1996). Our observations confirm the use of these hosts at this location, but also indicate that

Anemonefishes are well known for their ability to live unharmed among the stinging tentacles of sea anemones. This study examined whether there is ontogenetic and interspecific variation in the protection of anemonefishes from being stung by symbiotic anemones. Ontogenetic variation in protection was studied by determining if the tentacles of anemones would adhere to the eggs, larvae (0–5 days old), and recently metamorphosed anemonefish juveniles (7–14 days old). Interspecific variation in protection was examined by forcing juveniles of 10 species of anemonefishes to contact the tentacles of up to 9 anemone species. The tentacle adhesive forces of the anemone species were also measured. The eggs of anemonefishes were protected from all species of symbiotic anemones tested. Larval fishes were captured and killed by anemones, but recently metamorphosed juvenile fishes were protected from certain host species. Thus, the anemonefishes developed some form of protection during metamorphosis from a pelagic larva to a benthic juvenile. The juveniles of only one anemonefish species (Amphiprion percula) were protected from all the symbiotic anemone species tested, while most other anemonefish species were stung by at least one anemone species. The extreme host specialist, Premnas biaculeatus, was only protected from its natural host species (Entacmaea quadricolor) and was stung by 6 other symbiotic anemone species. The juveniles of all anemonefish species were protected from E. quadricolor, but only a few fish species were able to contact Stichodactyla gigantea without being stung. Fish that were stung by anemone species with strongly adhesive tentacles (e.g., S. gigantea, S. haddoni), were generally captured and killed. However, there was no correlation between the tentacle adhesive force of an anemone species and the number of anemonefish species that it stung.

Nine species of sea anemones ( Anthopleura asiatica , Actinia equina , Actinodendron arboreum , Phymanthus loligo , Entacmaea actinostoloides , Stichodactyla gigantea , S. haddoni , S. mertensii and Metridium senile ) contained arsenic in the range of 1.6–7.0 μg As g −1 (wet mass basis). Irrespective of the species, water-soluble arsenic compounds accounted for more than 80% of the total arsenic. Analysis of water-soluble arsenic compounds by LC/ESI-MS revealed that four arsenicals, arsenobetaine (AB), trimethylarsoniopropionate, arsenocholine (AC) and tetramethylarsonium ion (TEMA), are contained in most species but arsenate, methylarsonic acid, dimethylarsinic acid and trimethylarsine oxide are absent in all species. Interestingly, compositional patterns of the four arsenicals greatly differed from species to species. Only three species ( S. gigantea , S. haddoni and M. senile ) contained AB at the highest proportions, similar to the majority of marine animals. However, the remaining six species showed unusual compositional patterns of arsenic compounds; AC was most predominant in A. arboreum and P. loligo and TEMA in A. asiatica , A. equina , E. actinostoloides and S. mertensii . On the whole, high proportions (24.6–87.1% of the water-soluble arsenic) of TEMA appear to be a peculiar characteristic of many species of sea anemones. Thus, sea anemones are an important animal group in the arsenic cycling, especially in that they may be donors of TEMA to predators.

An epidermal growth factor (EGF)-like toxin (gigantoxin I) and two sodium channel toxins (gigantoxins II and III), previously isolated from the sea anemone Stichodactyla gigantea, were cloned for their cDNAs. The precursor protein of gigantoxin I is composed of a signal peptide, propart and mature peptide, similar to those of gigantoxins II and III, and is much simpler in structure than those of mammalian EGFs. In addition, gigantoxin I as well as gigantoxins II and III was demonstrated to be contained in nematocysts, suggesting that gigantoxin I functions as a toxin in S. gigantea.

The aims of this research were to discover the density of algae symbiont of zooxanthellae in the giant carpet anemone(Stichodactyla gigantea) from the nature and the asexual reproduction by longitudinal body fragmentation technique. Theresearch was conducted from October 2007 to July 2008, in The Hatchery of University of Hasanuddin Marine Station inBarrang Lompo Island for seed production and coral reefs area of Barrang Lompo Island for the implementation of culture.The series of study was started with parental collection and acclimatization of anemones, fragmentation of the body,culturing anemones in the coral reefs area and collection of algae zooxanthellae which is conducted every two months. Theresults of this study indicated the difference of zooxanthellae density from nature and asexual reproduction anemones. Thehighest density of zooxanthellae algae found in the non fragmented or nature population (AA) (10.84 x 10 6 cell/cm 2 ),followed by the anemone which was resulted from 2 parts body fragmentation (AF2) (10.24 x 10 6 cells/cm 2 ), and the anemonewhich was resulted from 4 parts body fragmentation (AF4) (9.17 x 10 6 cell/cm 2 ). Whereas, between the good coral (KB) andbad coral (KR) not significant. Keywords : fragmentation, sea anemones, Stichodactyla gigantea, zooxanthellae algae