Search Results (11)

The tropical coral Siderasterea radians is typically found in mangrove areas, seagrass beds, and environments tolerated by few other scleractinians in the Caribbean and South Florida. Siderastrea radians experience bleaching stress in Buttonwood Sound in Florida Bay during April–May, a time when the seawater is below bleaching temperatures. Stress first appears as a pink coloration due to the presence of fluorescent pigments protecting the coral tissue and algal symbionts from exposure to excessive sunlight/UV light. Surveys of S. radians in areas frequented by parrotfish showed that up to 38.5% of the corals were pink, with about a quarter of all the corals having bite marks. In areas not frequented by parrotfish, only 3.2% of the corals were pink, and none had bite marks. A seasonal analysis in parrotfish-frequented seawater showed S. radians contained among the lowest tissue biomass and density of symbiotic algae during April–May 2010–2017, often looking pink. It is hypothesized that seawater temperature is not the cause of bleaching in Buttonwood Sound during April–May but rather predation by the rainbow parrotfish Scarus guacamaia. Full article

Various photographs of the West Atlantic hoary rubble crab, Banareia palmeri (Rathbun, 1894), published on the internet show individuals being perched on branching octocorals. This habitat relationship has not been given attention in the scientific literature. The crab belongs to the brachyuran decapod family Xanthidae, which includes other species that associate with corals and zoantharians. Other aspects of the biology of B. palmeri, such as its diet, are unknown. During a night dive in Bonaire, an individual of B. palmeri was observed cutting off the tip of a sea rod, Pseudoplexaura sp., and pulling the loose fragment to its hiding place. The crab has also been observed in association with other octocoral species, such as Gorgonia ventalina Linnaeus, 1758. Close examination of the crab’s claws revealed that the inner edges resemble saws by bearing tooth-like structures with sharp edges, which explains how this animal is able to cut through the coral’s soft tissue and horny axis. These findings suggest that the crab is an expert in clipping octocoral branches, which may explain why some sea rod branches can be observed missing their original rounded tips and have regenerated pointy ends instead. Considering the octocoral’s regeneration capacity, it would be relevant to study how fast these branch tips are able to heal and whether fragments escaping from the crab’s claws are able to survive. Future examination of the crab’s gut contents and aquarium experiments may be able to provide more information about its dietary preferences. Full article

The corallivorous snails Coralliophila meyendorffii and its coral host Parazoanthus axinellae are appealing candidates for studying symbiotic interactions at the microbiome level. In this study, we investigated for the first time the microbial community in the stomach of C. meyendorffii and in the polyps of its coral host P. axinellae using as markers multiple regions of the 16S rRNA gene. The bacterial community in the stomach of another corallivorous snail, Babelomurex cariniferus, that feeds on Cladocora hexacorals, was also investigated for comparison. The obtained results indicated the phylum Proteobacteria as the most abundant among the analysed samples, with Alphaproteobacteria and Gammaproteobacteria as the main classes. Among the investigated communities, some bacterial taxa were recognised in line with previous findings in the microbiota of marine invertebrates. As both organisms are exposed to the same bacteria in their habitats, this might suggest shared environmental influences for their microbiota composition. Most of the detected taxa found exclusively or predominantly in P. axinellae samples suggest the presence of holobiont components within the microbial community of this coral, mirroring those identified in other corals, while the stomach microbiome of C. meyendorffii did not indicate a primary role in parasitism. Finally, we provide evidence that many of these bacterial taxa are horizontally transferred between Parazohantus and Corallliophila. Full article

A corallivorous nudibranch from the South China Sea reproduced explosively and caused extensive damage to Porites in our aquarium. In this study, morphological and molecular analyses of the nudibranch were conducted and described. Morphologically, this nudibranch was nearly consistent with Pinufius rebus in its characteristics intermediate between arminids and aeolids. The only detected difference was that the hook-like denticles on the masticatory border of P. rebus were absent in this nudibranch. In a molecular analysis, phylogenetic results based on the cytochrome oxidase subunit-I, 16S rRNA, and histone H3 gene sequences showed that this nudibranch and P. rebus form a well-supported sister clade under the superfamily Fionoidea, with significant interspecific divergence (0.18). Thus, we presumed that this nudibranch is a new species of Pinufius. Our results extend the distribution of Pinufius to the South China Sea, support the current taxonomic status of Pinufius under the superfamily Fionoidea, and imply that the species composition of Pinufius is more complex than previous records. Moreover, as a corallivorous nudibranch, the potential threat of Pinufius to coral health cannot be neglected. Full article

A biodiversity survey on three corallivorous snails (Mollusca: Gastropoda) was performed at 28 sites around the island of Bonaire to assess their distribution patterns and associated host corals. The snails and their hosts were identified and counted in three depth zones: 5–10, 10–20, and 20–30 m. The snails were Coralliophila galea and C. salebrosa (Muricidae: Coralliophilinae), and Cyphoma gibbosum (Ovulidae: Simniinae). All three species were widespread around the island without apparent interspecific geographical variation. Coralliophila galea was found exclusively on scleractinian corals, Coralliophila salebrosa almost exclusively on octocorals, and Cyphoma gibbosum only on octocorals. Coralliophila salebrosa showed more dietary overlap with Cyphoma gibbosum than with Coralliophila galea. Coralliophila galea was the most commonly encountered species with the largest number of host species. Owing to its hosts distribution, this species also showed a greater maximum depth and a wider bathymetrical range than the other two snails. The other two snails were shallower and their depth ranges did not differ significantly. Host-coral size did not seem to have influence on the number of snails per host. Coral damage caused by the snails was visible but appeared to be low, causing no mortality in Bonaire, which suggests that the relation with their hosts is more parasitic than predatory. Because these three corallivores have occasionally been reported to occur as outbreaks in other Caribbean localities and may act as vectors in the dispersal of coral diseases, it is recommended that future studies should focus on their population dynamics. Full article

Coral ingestion by crown-of-thorns starfish (COTS) is an important cause of coral reef degradation, although the impacts of COTS feeding on coral-associated microbial communities are not well understood. Therefore, in this study, we analyzed the coral tissue-weight, Symbiodiniaceae density (SD), bacterial community composition, and the predicted functions of bacterial genes associated with Pocillopora corals in healthy portions and feeding scars, following COTS feeding. Coral tissue-weight loss rate in the feeding scars was 71.3–94.95%. The SDs were significantly lower in the feeding scars, and the SD-loss rate was 92.05% ± 2.12%. The relative abundances of bacterial communities associated with Pocillopora corals after COTS feeding changed significantly and were almost completely reorganized at the phylum and genus levels. Analysis of the microbial metagenomic-functional capacities showed that numerous physiological functions of the coral-bacterial holobionts in the feeding scars were different, including amino acid metabolism, xenobiotic biodegradation and metabolism, lipid metabolism, membrane transport, signal transduction, and cell motility, and all these capacities could be corroborated based on metagenomic, transcriptomic or proteomic technologies. Overall, our research suggests that coral holobionts may be destroyed by COTS, and our findings imply that bacterial communities in feeding scars could affect the health of Pocillopora corals. Full article

The term corallivorous gastropod refers to a group of snails that feeds on coral and inhabits coral communities worldwide. Outbreaks of these species cause serious damage to coral communities. There are various reasons behind the outbreaks; however, further clarifications are needed. It may be possible to predict outbreaks by measuring the number of floating larvae of corallivorous gastropods in seawater. Drupella fragum is the most damaging species in Japan, so we produced antibodies against D. fragum larvae in order to easily detect this species in the field. Antibody specificity analysis in aquarium-hatched corallivorous gastropods showed a higher specificity against D. fragum compared to D. cornus. A field study using the antibody showed that many D. fragum larvae were detected from June to November at all stations. The larvae at the Shirigai station were collected in June and July in large numbers compared to the other stations. Large groups of D. fragum were collected around the sampling point in Shirigai in September 2016. Our results imply that there is a possibility that outbreaks could be predicted using this antibody. Full article

Coral reefs are among the most biodiverse biological systems on earth. Corals are classified as marine invertebrates and filter the surrounding food and other particles in seawater, including pathogens such as viruses. Viruses act as both pathogen and symbiont for metazoans. Marine viruses that are abundant in the ocean are mostly single-, double stranded DNA and single-, double stranded RNA viruses. These discoveries were made via advanced identification methods which have detected their presence in coral reef ecosystems including PCR analyses, metagenomic analyses, transcriptomic analyses and electron microscopy. This review discusses the discovery of viruses in the marine environment and their hosts, viral diversity in corals, presence of virus in corallivorous fish communities in reef ecosystems, detection methods, and occurrence of marine viral communities in marine sponges. Full article

The architectural complexity of coral-reef habitat plays an important role in determining the assemblage structure of reef fish. We investigated associations between the reef habitats and fish assemblages in the Northwestern Hawaiian Islands (NWHI) using in situ fish counts and data on habitat metrics and benthic community composition that were obtained from three-dimensional (3D) photogrammetric reconstructions of the surveyed sites. The structure of fish assemblage as a whole on the basis of Bray–Curtis dissimilarity, species richness and the abundances of herbivores and piscivores were associated with habitat metrics, with higher levels of architectural complexity generally supporting greater numbers of fish species and individuals. Benthic cover did not explain additional variation in these variables after the effects of habitat metrics were taken into account. Corallivorous fish was the only group that showed positive associations with both habitat metrics and benthic cover (Acropora and Pocillopora corals). The total fish abundance and the abundances of planktivores and invertivores did not show associations with either habitat metrics or benthic cover. This study suggests that an appropriate combination of habitat metrics can be used to account sufficiently for the effects of habitat architecture on fish assemblages in reef monitoring efforts in the NWHI. Full article

The corallivorous crown-of-thorns starfish (Acanthaster spp.) is a major cause of coral mortality on Indo-Pacific reefs. Despite considerable research into the biology of crown-of-thorns starfish, our understanding of the early post-settlement life stage has been hindered by the small size and cryptic nature of recently settled individuals. Most growth rates are derived from either laboratory studies or field studies conducted in Fiji and Japan. The Great Barrier Reef (GBR) is currently experiencing its fourth recorded outbreak and population models to inform the progression of outbreaks lack critical growth rates of early life history stages. High numbers of 0+ year juveniles (n = 3532) were measured during extensive surveys of 64 reefs on the northern GBR between May and December 2015. An exponential growth model was fitted to the size measurement data to estimate monthly ranges of growth rates for 0+ year juveniles. Estimated growth rates varied considerably and increased with age (e.g., 0.028–0.041 mm·day⁻¹ for one-month-old juveniles versus 0.108–0.216 mm·day⁻¹ for twelve-month-old juveniles). This pioneering study of 0+ year juveniles on the GBR will inform population models and form the basis for more rigorous ongoing research to understand the fate of newly settled Acanthaster spp. Full article

Coral reef ecosystems are increasingly subject to severe, large-scale disturbances caused by climate change (e.g., coral bleaching) and other more direct anthropogenic impacts. Many of these disturbances cause coral loss and corresponding changes in habitat structure, which has further important effects on abundance and diversity of coral reef fishes. Declines in the abundance and diversity of coral reef fishes are of considerable concern, given the potential loss of ecosystem function. This study explored the effects of coral loss, recorded in studies conducted throughout the world, on the diversity of fishes and also on individual responses of fishes within different functional groups. Extensive (>60%) coral loss almost invariably led to declines in fish diversity. Moreover, most fishes declined in abundance following acute disturbances that caused >10% declines in local coral cover. Response diversity, which is considered critical in maintaining ecosystem function and promoting resilience, was very low for corallivores, but was much higher for herbivores, omnivores and carnivores. Sustained and ongoing climate change thus poses a significant threat to coral reef ecosystems and diversity hotspots are no less susceptible to projected changes in diversity and function. Full article