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Corals and gorgonians play an important role as ecosystem engineers in many sublittoral communities worldwide. However, coral populations are being increasingly impacted by human activities. Active ecological restoration is a popular conservation tool nowadays, widely used to revert degradation in natural populations. Several studies have reported survival and growth success in actively restored corals, but few have studied the long‐term effect of transplantation on coral reproduction. We investigated survival and sexual reproduction of transplanted colonies of the Mediterranean gorgonian Eunicella singularis up to 3 years after being recovered from fishery bycatch and transplanted back to their habitat. Three different colony sizes were tested to explore possible effects of fragmentation on survival and reproduction. Results showed that transplanted colonies suffered a significant mortality during the first 4–5 months (30–35%), independently of fragment size. However, larger fragments showed high survival despite other disturbances, as a bloom of ephemerons filamentous algae occurred during the study. Results also showed that reproductive capacity is negatively affected by transplantation in female colonies. Conversely, male colonies were not directly affected by transplantation but showed an unexpectedly reduced number of spermary sacs both in transplanted and natural control colonies. The trade‐off between investment in reproduction and mortality of transplants highlights that large colony size could be the most appropriate for the active restoration of E. singularis. This study emphasizes the need to explore the long‐term viability and the reproduction investment in transplanted corals as indicators of restoration success, whose populations are sustained by sexual reproduction. [ABSTRACT FROM AUTHOR]

Microbes perform critical functions in corals, yet most knowledge is derived from the photic zone. Here, we discover two mollicutes that dominate the microbiome of the deep-sea octocoral, Callogorgia delta, and likely reside in the mesoglea. These symbionts are abundant across the host's range, absent in the water, and appear to be rare in sediments. Unlike other mollicutes, they lack all known fermentative capabilities, including glycolysis, and can only generate energy from arginine provided by the coral host. Their genomes feature several mechanisms to interact with foreign DNA, including extensive CRISPR arrays and restriction-modification systems, which may indicate their role in symbiosis. We propose the novel family Oceanoplasmataceae which includes these symbionts and others associated with five marine invertebrate phyla. Its exceptionally broad host range suggests that the diversity of this enigmatic family remains largely undiscovered. Oceanoplasmataceae genomes are the most highly reduced among mollicutes, providing new insight into their reductive evolution and the roles of coral symbionts. Corals and other marine invertebrates host diverse microbes that remain poorly characterized, especially in the deep sea. Here the authors discover a new clade of bacteria with uniquely streamlined genomes in the tissue of a deep-sea coral that provide insights into the genome reduction of symbionts. [ABSTRACT FROM AUTHOR]

Background: Corals are the foundational species of coral reefs and coralligenous ecosystems. Their success has been linked to symbioses with microorganisms, and a coral host and its symbionts are therefore considered a single entity, called the holobiont. This suggests that there may be evolutionary links between corals and their microbiomes. While there is evidence of phylosymbiosis in scleractinian hexacorals, little is known about the holobionts of Alcyonacean octocorals. Results: 16S rRNA gene amplicon sequencing revealed differences in the diversity and composition of bacterial communities associated with octocorals collected from the mesophotic zones of the Mediterranean and Red Seas. The low diversity and consistent dominance of Endozoicomonadaceae and/or Spirochaetaceae in the bacterial communities of Mediterranean octocorals suggest that these corals may have a shared evolutionary history with their microbiota. Phylosymbiotic signals were indeed detected and cophylogeny in associations between several bacterial strains, particularly those belonging to Endozoicomonadaceae or Spirochaetaceae, and coral species were identified. Conversely, phylosymbiotic patterns were not evident in Red Sea octocorals, likely due to the high bacterial taxonomic diversity in their microbiota, but cophylogeny in associations between certain coral and bacterial species was observed. Noteworthy were the associations with Endozoicomonadaceae, suggesting a plausible evolutionary link that warrants further investigations to uncover potential underlying patterns. Conclusions: Overall, our findings emphasize the importance of Endozoicomonadaceae and Spirochaetaceae in coral symbiosis and the significance of exploring host-microbiome interactions in mesophotic ecosystems for a comprehensive understanding of coral-microbiome evolutionary history. [ABSTRACT FROM AUTHOR]

The effects of climate change are now more pervasive than ever. Marine ecosystems have been particularly impacted by climate change, with marine heatwaves (MHWs) being a strong driver of mass mortality events. Even in the most optimistic greenhouse gas emission scenarios, MHWs will continue to increase in frequency, intensity and duration. For this reason, understanding the resilience of marine species to the increase of MHWs is crucial to predicting their viability under future climatic conditions. In this study, we explored the consequences of MHWs on the resilience (the ability of a population to resist and recover after a disturbance) of a Mediterranean key octocoral species, Paramuricea clavata, to further disturbances to their population structure. To quantify P. clavata's capacity to resist and recover from future disturbances, we used demographic information collected from 1999 to 2022, from two different sites in the NW Mediterranean Sea to calculate the transient dynamics of their populations. Our results showed that the differences in the dynamics of populations exposed and those not exposed to MHWs were driven mostly by differences in mean survivorship and growth. We also showed that after MHWs P. clavata populations had lower resistance and slower rates of recovery than those not exposed to MHWs. Populations exposed to MHWs had lower resistance elasticity to most demographic processes compared to unexposed populations. In contrast, the only demographic process showing some differences when comparing the speed of recovery elasticity values between populations exposed and unexposed to MHWs was stasis. Finally, under scenarios of increasing frequency of MHWs, the extinction of P. clavata populations will accelerate and their capacity to resist and recover after further disturbances will be hampered. Overall, these findings confirm that future climatic conditions will make octocoral populations even more vulnerable to further disturbances. These results highlight the importance of limiting local impacts on marine ecosystems to dampen the consequences of climate change. [ABSTRACT FROM AUTHOR]

Xeniidae is a soft coral family that has contributed to the diversity of tropical coral reef communities, including those found in Southeast Asia. From 50 soft coral samples of the family Xeniidae collected from coastal fringing reefs along the coast of central Vietnam, five species have been recorded belonging to two genera, Xenia (two species) and Heteroxenia (three species). Of five species, two were recorded for the first time in Vietnam are Xenia novaebritaniae Ashworth, 1900 and Heteroxenia elisabethae Kölliker, 1874. An identification key was provided based on colony forms and morphological characters of sclerites for five xeniid corals in Vietnam. [ABSTRACT FROM AUTHOR]

Deep-sea corals are rarely identified to species due to a lack of taxonomic expertise and paucity of sampling. Herein we describe a new genus from the family Keratoisididae collected from the Northeast Atlantic. Using both nuclear (2010 conserved element loci) and complete mitogenome phylogenies, we found this genus to be closely related to the genera Dokidisis and Jasonisis. In the nuclear phylogeny, each genus occupied a distinct well-supported clade. All three genera lack thorned- or double-star sclerites in the pharynx; instead they have flattened rods, a potential unifying feature of the keratoisidid group J3 of Watling et al. (2022). The newly described genus Explorisis gen. nov. has a unique sclerome including spindles and tapered rods that differentiates it from its sister genera. Explorisis katharina sp. nov. is characterised by volcano to cylindrical shaped polyps, striated rods and spindles in the polyp body, and elongated flattened rods in the coenenchyme, whereas Explorisis poppyae sp. nov. has heavily granulated spindles and rods in both the polyp body and coenenchyme. Genetic variation within the mitogenomes across both Explorisis gen. nov. species is limited with mutations in just 3 of 14 protein coding regions. ZooBank: Deep-sea corals are often not identified to species rank due to a lack of taxonomic expertise. Bamboo corals are an exclusively deep sea and prolific group of corals found in every ocean basin. In this study, we describe a new genus and two new species of bamboo coral from the Northeast Atlantic. By analysing both their morphology and DNA, we determined that this newly identified genus, named Explorisis, is closely related to the genera Dokidisis and Jasonisis. (Image credit: Declan Morrissey.) [ABSTRACT FROM AUTHOR]

Cnidome morphology appears to be a valuable tool for anthozoan (Octocarallia, Ceriantharia, and Hexacorallia) taxonomy. Ceriantharian cnidomes consist of b-mastigophores, isorhizas, spirocysts, and ptychocysts, including different subtypes. The b-mastigophores are the most valuable ceriantharian cnidae for species identification. The Ceriantharian b-mastigophore terminology is congruent to the b-mastigophores of Carlgren, b-rhabdoids, including the "faltstück" of Schmidt, spirulae, and also potentially the penicilli of den Hartog. The apical tightly folded, inverted b-mastigophore shafts, the "faltstück", are important species-specific characteristics due to their various patterns. The mesenterial structures known as craspedonemes, cnidorages, and acontioids also have high taxonomic value. Drop-shaped b-mastigophores might be characteristic nematocysts for mesenteries. The occurrence of isorhizas and striations on the inner ptychocyst capsule walls are other species' characteristics. The morphological similarities of spirulae and penicilli to b-mastigophores within Hexacorallia are highlighted by naming spirulae and penicilli as b-mastigophores/spirulae and b-mastigophores/penicilli subtypes, respectively. The slight morphological distinction between spirulae and penicilli will doubtfully justify the suborders Spirularia and Penicillaria. The spirocysts presence in Ceriantharia and Hexacorallia indicates a closer relationship between Ceriantharia and Hexacorallia than between Ceriantharia and Octocorallia. Octocorallia are the only anthozoans without spirocysts. This work underlines the importance of cnidome morphological analysis for taxonomic identification and classification. [ABSTRACT FROM AUTHOR]

The complete mitochondrial genome of Paragorgia papillata Li et al. 2021, a deep-sea gorgonian inhabiting at 858 m in Caroline Ridge, was obtained in this study. The length of the mitochondrial genome is 19,018 bp with 14 protein coding genes, one transfer RNA (tRNA-Met) and two ribosomal RNA genes contained in this circular molecule. Phylogenetic analysis indicated that P. papillata and P. coralloides Bayer, 1993 were two closely related species, and a total of 26 mutational sites (four nonsynonymous mutations included) can be detected between their mitochondrial genomes. This exhibits a case that mitochondrial genomes can be applied to differentiate closely related species in gorgonians. The phylogenetic tree constructed with mitochondrial genomes showed that the families in Octocorallia are reciprocally monophyletic, provided that the family names were revised according to the systematic revision of Octocorallia guided by phylogenomics. However, the relationships of the families within each order were different between the previous phylogenomic work and ours. Integrating mitochondrial genomes from a wider array of Octocorallia families is essential for a more accurate comparison of phylogenies derived from nuclear and mitochondrial sequences in future study. [ABSTRACT FROM AUTHOR]

A new species and genus of colonial coral, Lindaphylon solovjevi, from the Upper Ordovician of Estonia is described in detail. The colony has a zonation similar to the zonation structure of the mesogleal skeleton of octocorals, since it consists of a narrow axis and a surrounding wide cortex of small calcite sclerites and a system of large solenia. Corallites present 12 sclerosepta in a wide shallow cup. A new family Lindaphylonidae and an order Lyndaphylonaceae are based on these features, and a new order placed in the subphylum Anthozoa as incertae sedis. A comparative study of skeleton formation and mesenteric apparatus symmetry in different groups of coral polyps is considered in detail. [ABSTRACT FROM AUTHOR]

The complete mitochondrial genome of Paragorgia papillata Li et al. 2021, a deep-sea gorgonian inhabiting at 858 m in Caroline Ridge, was obtained in this study. The length of the mitochondrial genome is 19,018 bp with 14 protein coding genes, one transfer RNA (tRNA-Met) and two ribosomal RNA genes contained in this circular molecule. Phylogenetic analysis indicated that P. papillata and P. coralloides Bayer, 1993 were two closely related species, and a total of 26 mutational sites (four nonsynonymous mutations included) can be detected between their mitochondrial genomes. This exhibits a case that mitochondrial genomes can be applied to differentiate closely related species in gorgonians. The phylogenetic tree constructed with mitochondrial genomes showed that the families in Octocorallia are reciprocally monophyletic, provided that the family names were revised according to the systematic revision of Octocorallia guided by phylogenomics. However, the relationships of the families within each order were different between the previous phylogenomic work and ours. Integrating mitochondrial genomes from a wider array of Octocorallia families is essential for a more accurate comparison of phylogenies derived from nuclear and mitochondrial sequences in future study.

Shallow water coral reefs in many parts of the world are experiencing phase shifts due to various disturbances, resulting in increases in the abundance of algal assemblages and non-scleractinian taxa, including soft corals (Octocorallia). However, the effects of these changes on reef-associated macrofauna are still not fully understood. In this study, (1) structures of fish assemblages in shallow coral reefs with varying degrees of soft coral and hard coral dominance in Okinawa Island (Japan) were characterized, and (2) the influences of hard and soft coral cover on fish species richness, abundances, and patterns in community composition at the species and trophic group levels were examined. Tests revealed that fish species richness and abundance were significantly lower at soft coral-dominated sites compared to hard coral-dominated sites. Interestingly, these variables did not differ between soft coral- and turf algae-dominated sites. Hard coral cover had a positive relationship with fish species richness and abundance, and although nonsignificant, soft coral cover showed a negative trend in terms of its relationship with those two fish assemblage variables. Both hard coral and soft coral covers significantly influenced patterns of fish community composition among the sites, but not turf algae. Generally, this study shows that the loss of hard coral cover and increase in soft coral cover may lead to changes in community structure and potentially decreased abundance and diversity of reef fishes. The results of this study should be useful in predicting the future state of fish assemblages in the coral reefs of Okinawa Island, which are continuously threatened by various disturbances that may lead to major changes in the structure of benthic communities. [ABSTRACT FROM AUTHOR]

The timing of larval production and release of organisms is important in understanding their presence and prevalence in the environment. On the subtropical coral reefs around Okinawa Island, Japan, the reproductive timing of many soft coral species is still largely unknown. In this study, we report the first documentation of in situ external brooding and planulae release of a stoloniferan octocoral observed on the coral reefs of Okinawa Island. We observe external brooding of embryos and developing larvae on the colony surface and the subsequent planulation of some azooxanthellate larvae of Clavularia cf. inflata from two coral reef sites in the northwestern region of Okinawa Island. These observations indicate that this species reproduces concurrently with other zooxanthellate coral reef anthozoans in the summer season. [ABSTRACT FROM AUTHOR]

In the Caribbean, reef-building scleractinian corals have declined precipitously and octocorals have emerged as one of their main successors. The success of octocorals and the formation of octocoral forests has been attributed to their continuing recruitment to reef habitats, as well as tolerance to pollution, reduced direct competition with scleractinians, and resistance and resilience to climatic events. Benthic grazers on coral reefs can facilitate the growth and recruitment of corals by reducing the abundance of competitive algal turfs and macroalgae. However, grazing can also hinder corals through sublethal damage to coral tissue and predation of recruits. We assessed the effects of grazing by fishes and the sea urchin Diadema antillarum as well as predation by mesofauna on octocoral recruitment through a series of manipulative in situ and ex situ experiments. Exposure to fish and urchin grazing significantly reduced the post-settlement survival of octocoral recruits, while turf-associated mesofauna did not significantly affect recruitment. We also found a positive relationship between octocoral recruitment and the abundance of turf algae, which may reflect the deleterious effect of grazing on both turf algae and octocoral recruits. These data suggest that grazers and predators mediate the bottleneck characteristic of recruitment, primarily through their effect on post-settlement survival. Thus, the declines in the abundance of grazing fishes and urchins throughout the Caribbean may have contributed to the increase in Caribbean octocoral abundance, concurrent with the loss of scleractinians. [ABSTRACT FROM AUTHOR]

Caribbean coral reefs are currently facing a rapid decline caused by a plethora of threats including disease outbreaks. Octocorals appear to be unaffected by the majority of diseases impacting scleractinian corals, including stony coral tissue loss disease (SCTLD) that emerged in 2014 and resulted in a mass mortality of scleractinian coral populations inhabiting Florida, the USA, and Caribbean reefs. Although the Caribbean Sea is considered a disease hot spot, few investigations into the mechanism(s) responsible for the resistance of octocorals have been conducted. In response, the capacity for octocoral-derived extracts and natural products to inhibit strains of Vibrio coralliilyticus, pathogenic bacteria that can cause bleaching and disease in stony corals and can co-occur in SCTLD infections, was explored. Extracts obtained from each of the four octocoral species studied demonstrated antimicrobial activity against V. coralliilyticus. Bioassay-guided fractionations of crude extracts from Antillogorgia americana were employed to identify the antimicrobial compounds, revealing the presence of secosterols in the most bioactive fractions. These results suggest that octocoral species may utilize chemical defenses to protect themselves against infection by strains of a known coral pathogen and contribute to the body of knowledge regarding the success of octocorals on Caribbean reefs. [ABSTRACT FROM AUTHOR]

Nudibranch mollusks, which are well-known for their vivid warning coloration and effective defenses, are mimicked by diverse invertebrates to deter predation through both Müllerian and Batesian strategies. Despite extensive documentation across different taxa, mimickers have not been detected among annelids, including polychaetes, until now. This study described a new genus and species of polychaete living on Dendronephthya octocorals in Vietnam and Japan. Belonging to Syllidae, it exhibits unique morphological adaptations such as a low number of body segments, simple chaetae concealed within the parapodia and large and fusiform antennae and cirri. Moreover, these appendages are vividly colored, featuring an internal dark red area with numerous terminal white spots and bright yellow tips, effectively contributing to mimicking the appearance of a nudibranch. This discovery not only documents the first known instance of such mimicry among annelids, but also expands our understanding of evolutionary adaptation and ecological strategies in marine invertebrates. [ABSTRACT FROM AUTHOR]

Historically isolated from tropical influences, the Mediterranean Sea underwent drastic changes, including the Lessepsian migration facilitated by the opening of the Suez Canal, connecting the Red Sea to the Mediterranean Sea. Here, we report on the discovery of a thriving and lush population of an Indo‐Pacific soft coral in the transforming Mediterranean Sea. This species was identified as Dendronephthya hemprichi (Klunzinger, 1877) through morphological and genetic assessments. The unexpected appearance of a dense population of this tropical coral off the Israeli Mediterranean coast signifies a northward range expansion of approximately 350 km from the northern Red Sea. Considering the potential for this soft coral to alter benthic community structure and create new marine animal forests, the population's sudden and massive colonization of artificial structures raises intriguing questions about its possible long‐term ecological implications in the Mediterranean ecosystem. This study emphasizes the urgency of continuous monitoring and research to understand the ecological consequences of this unprecedented abrupt tropical incursion of hundreds of colonies and its potential implications for the region's biodiversity. Moreover, the findings contribute to the broader discourse on the tropicalization of temperate and subtropical regions, highlighting the need to adapt conservation strategies that embrace and understand novel configurations of ecosystems in the face of ongoing local and global changes. [ABSTRACT FROM AUTHOR]

The reproductive biology of the branching octocoral Antillogorgia americana was studied at a site on the Caribbean coast of Panama in 1990–1991 by examining the reproductive status of 11 colonies across 14 months. Colonies were gonochoric. The presence of large and mature eggs or spermaries was allochronic across colonies and months, with peak gonad volumes occurring in months ranging from October through May. Reproductive effort varied between branches on a colony, with variation between branches and branchlets accounting for 25% of the random variation between polyps. Branchlets at the tip of the colony had fewer mature eggs than those lower on the branch, and polyps at the tips of the branchlets had fewer still. Although the simultaneous release of eggs and sperm is critical to reproductive success, the lack of synchrony among colonies on the scale of months may reflect less need for all colonies to spawn in a single event among abundant species that release large numbers of gametes. Such a strategy also spreads the risk of reproductive failure due to environmental conditions during any single month. The presence of multiple spawning episodes can also drive the reproductive isolation of populations and may reflect the presence of cryptic species within the taxon. Studies of reproductive timing can be an important adjunct in identifying variation in life history strategies as well as assessing the validity of species boundaries. [ABSTRACT FROM AUTHOR]

Global warming causes functional shifts and reorganisation in marine communities through range shifts to high-latitude reefs and cnidarian bleaching mortality in the tropics. Such changes threaten the integrity and structure of marine communities, especially as foundational and associated species are reduced or lost. However, comparatively little is known about the extent of range shifts and their ecological consequences for the overlooked components of marine ecosystems, such as octocorals and zoantharians (O + Z) on shallow coral reefs. As these groups play a crucial part in building complexity and sustaining life in reef communities, functional shifts in these taxa may cascade through the entire ecosystem, but these processes have not been quantified. Here, we examined the environmental drivers and functional consequences of spatial variation in octocoral and zoantharian communities across 27 sites in southern Japan, spanning from tropical to warm-temperate waters. We collated a trait database for 42 entities (species, genus, and family level identifications) of octocorals and zoantharians and calculated functional diversity and functional richness to measure functional compositional change. We identified five functional groups according to their trait similarities and identified how their abundances respond to changing environmental factors with general additive models (GAMs). We found functional shifts among octocorals and zoantharians across the tropical to temperate thermal gradient, with the abundances of two functional groups best explained by gradients in minimum sea surface temperature. Non-linear relationships between the functional groups and thermal gradients imply a more intricate relationship than expected, suggesting other non-temperature-based drivers, e.g., nitrogen or pH levels might also play an important role. Only functional group richness and species richness showed significant correlations with latitude, whilst functional diversity and functional richness did not. Our results indicate that octocoral and zoantharian communities and functionality potentially undergo shifts with clear community compositional changes, influenced by climate change across environmental gradients. However, the taxonomy and identification of these taxa remain difficult, and information on functional traits is often sparse or not species-specific, indicating a clear need for further basic zoological and ecological work on octocorals and zoantharians. [ABSTRACT FROM AUTHOR]

This article reports three new records of soft corals, viz. Sarcophyton boletiforme Tixier-Durivault 1958; S. cinereum Tixier-Durivault 1946; and S. turschi Verseveldt 1976, from the Andaman and Nicobar Islands, India. The specimens were collected from coral reef regions, to a depth of 25 m. Species identification involved a detailed analysis of colony morphology, sclerite structures, and measurements taken from various parts of the colony. Sarcophyton boletifome features club-shaped sclerites (up to 0.38 mm) on capitulum and stalk surfaces, and spindle-shaped sclerites (up to 1.10 mm) in the stalk interior; S. cinereum exhibits warty club-shaped sclerites, in the capitulum surface layer (0.17–0.27 mm) and in the base surface layer (0.10–0.55 mm); and stalk interior features curved or straight spindles (up to 1.77 mm). The capitulum of S. turchi bears club-shaped surface sclerites, ranging in size from 0.09 to 0.38 mm, while the stalk interior contains spindle-shaped structures ranging from 0.35 to 0.75 mm. In a time when octocorals are threatened, it is refreshing to find octocoral species that are new to the Andaman and Nicobar Islands. These islands remain amongst the most ecologically significant in the Indo-Pacific region and should be protected. [ABSTRACT FROM AUTHOR]

Members of the genus Pseudopterogorgia Kükenthal, 1919 are widely distributed in shallow water of the Indo-West Pacific. During an investigation of benthic biodiversity in the subtidal zone surrounding the Nanji Islands in the East China Sea, two specimens of Pseudopterogorgia were collected and described as a new species based on an integrated morphological-molecular approach. Pseudopterogorgia nanjiensis sp. nov. is most similar to P. fredericki Williams & Vennam, 2001 in the irregular branching form and indistinct scaphoids, but differs by the coenenchymal sclerite content of distinct capstans and a few warty spindles and radiates (vs. mostly warty spindles and a few capstans), and a purplish colony (vs. white, pink to deep rose). Molecular phylogenetic analyses, based on the mtMutS - COI gene sequences, delineated a monophyletic clade encompassing all assessed Pseudopterogorgia species. Within this clade, P. nanjiensis sp. nov. showed a close phylogenetic affinity with both P. fredericki and P. australiensis Ridley, 1884. [ABSTRACT FROM AUTHOR]

Mollusk death assemblages are formed by shell remnants deposited in the surficial mixed layer of the seabed. Diversity patterns in tropical marine habitats still are understudied; therefore, we aimed to investigate the taxonomic, phylogenetic, and functional diversity of mollusk death assemblages at regional and local scales in coral reef sands and seagrass meadows. We collected sediment samples at 11 sites within two shallow gulfs in the Northwestern Caribbean Sea and Southeastern Gulf of Mexico. All the shells were counted and identified to species level and classified into biological traits. We identified 7113 individuals belonging to 393 species (290 gastropods, 94 bivalves, and nine scaphopods). Diversity and assemblage structure showed many similarities between gulfs given their geological and biogeographical commonalities. Reef sands had higher richness than seagrasses likely because of a more favorable balance productivity-disturbance. Reef sands were dominated by epifaunal herbivores likely feeding on microphytobenthos and bysally attached bivalves adapted to intense hydrodynamic regime. In seagrass meadows, suspension feeders dominated in exposed sites and chemosynthetic infaunal bivalves dominated where oxygen replenishment was limited. Time averaging of death assemblages was likely in the order of 100 years, with stronger effects in reef sands compared to seagrass meadows. Our research provides evidence of the high taxonomic, phylogenetic, and functional diversity of mollusk death assemblages in tropical coastal sediments as result of the influence of scale-related processes and habitat type. Our study highlights the convenience of including phylogenetic and functional traits, as well as dead shells, for a more complete assessment of mollusk biodiversity. [ABSTRACT FROM AUTHOR]

Numerous genomic methods developed over the past two decades have enabled the discovery and extraction of orthologous loci to help resolve phylogenetic relationships across various taxa and scales. Genome skimming (or low‐coverage genome sequencing) is a promising method to not only extract high‐copy loci but also 100s to 1000s of phylogenetically informative nuclear loci (e.g., ultraconserved elements [UCEs] and exons) from contemporary and museum samples. The subphylum Anthozoa, including important ecosystem engineers (e.g., stony corals, black corals, anemones, and octocorals) in the marine environment, is in critical need of phylogenetic resolution and thus might benefit from a genome‐skimming approach. We conducted genome skimming on 242 anthozoan corals collected from 1886 to 2022. Using existing target‐capture baitsets, we bioinformatically obtained UCEs and exons from the genome‐skimming data and incorporated them with data from previously published target‐capture studies. The mean number of UCE and exon loci extracted from the genome skimming data was 1837 ± 662 SD for octocorals and 1379 ± 476 SD loci for hexacorals. Phylogenetic relationships were well resolved within each class. A mean of 1422 ± 720 loci was obtained from the historical specimens, with 1253 loci recovered from the oldest specimen collected in 1886. We also obtained partial to whole mitogenomes and nuclear rRNA genes from >95% of samples. Bioinformatically pulling UCEs, exons, mitochondrial genomes, and nuclear rRNA genes from genome skimming data is a viable and low‐cost option for phylogenetic studies. This approach can be used to review and support taxonomic revisions and reconstruct evolutionary histories, including historical museum and type specimens. [ABSTRACT FROM AUTHOR]

The recent rise in ocean temperatures, accompanied by other environmental changes, has notably increased the occurrence and spread of diseases in Octocorallia, many species of which are integral to shallow tropical and subtropical coral reef ecosystems. This study focuses on the understanding of these diseases, which has been largely limited to symptomatic descriptions, with clear etiological factors identified in only a fraction of cases. A key example is the multifocal purple spots syndrome (MFPS) affecting the common Caribbean octocoral sea fan Gorgonia ventalina, linked to the gall-forming copepods of the genus Sphaerippe, a member of the widespread family, Lamippidae. The specialized nature of these copepods as endoparasites in octocorals suggests the potential for the discovery of similar diseases across this host spectrum. Our investigation employed four molecular markers to study disease hotspots in Saint Eustatius, Curaçao, northwest and southwest Cuba, and Bonaire. This led to the discovery of a group of copepod species in these varied Caribbean locations. Importantly, these species are morphologically indistinguishable through traditional methods, challenging established taxonomic approaches. The observed diversity of symbionts, despite the host species' genetic uniformity, is likely due to variations in larval dispersal mechanisms. Our phylogenetic analyses confirmed that the Lamippidae copepods belong to the order, Poecilostomatoida (Copepoda), and revealed their sister group relationship with the Anchimolgidae, Rhynchomolgidae, and Xarifiidae clades, known for their symbiotic relationships with scleractinian corals. These results add to our understanding of the evolutionary and ecological interactions of copepods and their hosts, and the diseases that they cause, and are important data in a changing climate. [ABSTRACT FROM AUTHOR]

In vivo studies of the effects of molecules of interest, such as hormones or xenobiotics on corals, are essential to uncover their effects on coral biological processes. However, exposure to such molecules is very challenging in aquarium systems due to the duration of exposure, the high cost of the compounds, their quantity, and their diffusion in seawater. In this study, we provide a durable alternative method by in vivo injection. The aim of this study was to evaluate slow release and local injection as a novel method of delivering compounds to corals. In this method, coconut oil, which solidifies upon injection and has a melting point of about 24°C, is used as the vehicle for injection. Local diffusion of the injected products in the organism was followed using visual tracers. Specifically, two classes of fluorescent markers were used, one of which examined internalization into cells (rhodamine), while the others were used as an application to monitor the calcification process (alizarin, calcein). In parallel, we developed an analytical method to quantify the calcein and alizarin labeling of sclerites, which allowed us to determine calcification rates in different parts of the coral. Two octocorals were used to optimize these methods, with Sarcophyton sp. being the preferred organism to develop and validate the injection procedures and characterize the diffusion of the markers. Once the method was perfected, injections were performed on the precious coral Corallium rubrum to prove the transferability of the method. [ABSTRACT FROM AUTHOR]

Bioluminescence is a widespread phenomenon that has evolved multiple times across the tree of life, converging among diverse fauna and habitat types. The ubiquity of bioluminescence, particularly in marine environments where it is commonly used for communication and defense, highlights the adaptive value of this trait, though the evolutionary origins and timing of emergence remain elusive for a majority of luminous organisms. Anthozoan cnidarians are a diverse group of animals with numerous bioluminescent species found throughout the world's oceans, from shallow waters to the light-limited deep sea where bioluminescence is particularly prominent. This study documents the presence of bioluminescent Anthozoa across depth and explores the diversity and evolutionary origins of bioluminescence among Octocorallia—a major anthozoan group of marine luminous organisms. Using a phylogenomic approach and ancestral state reconstruction, we provide evidence for a single origin of bioluminescence in Octocorallia and infer the age of occurrence to around the Cambrian era, approximately 540 Ma—setting a new record for the earliest timing of emergence of bioluminescence in the marine environment. Our results further suggest this trait was largely maintained in descendants of a deep-water ancestor and bioluminescent capabilities may have facilitated anthozoan diversification in the deep sea. [ABSTRACT FROM AUTHOR]

To optimize fragmentation approaches for restoration applications, this study assessed fragmentation size influences on health and growth rates of mesophotic octocorals. Growth rates for Swiftia exserta (n=6) and Muricea pendula (n=9) were determined using photogrammetry in a mesocosm over a 90-day trial. No significant difference was found in growth between fragmented size classes (3, 6, and 12 cm) (S. exserta p=0.156, M. pendula p=0.393). There was a significant difference (p=0.013) in growth rates between species, with faster annual growth (mean ± SE) for S. exserta (1.490 ± 0.399 cm/year) than for M. pendula (0.550 ± 0.228 cm/year). Fragments from healthy source colonies remained healthy, while fragments from an unhealthy colony experienced tissue loss. Healthy colonies may successfully be used for fragmentation in laboratory propagation, though optimal fragment size for restoration remains debatable. Use of laboratory-based propagation techniques to recover injured species may require better understanding of factors influencing growth. [ABSTRACT FROM AUTHOR]

Current efforts to halt the decline of biodiversity are based primarily on protecting species richness. This narrow focus overlooks key components of biological diversity, particularly the infra-species genetic diversity, which is critical to consider with respect to genetic adaptation in changing environments. While comparative population genetics is recognized as a relevant approach to improve biodiversity management, it is still barely considered in practice. Here, a comparative population genetics study was conducted on two key habitat-forming octocoral species, Corallium rubrum and Paramuricea clavata, to contribute to management of two Marine Protected Areas (MPAs) in the northwestern Mediterranean. Contrasting patterns of genetic diversity and structure were observed in the two species, although they share many common biological features and live in similar habitats. Differential genetic drift effects induced by species-specific reproductive strategies and demographic histories most likely explain these differences. The translation of our results into management strategies supports the definition of four management units. We identified a coldspot of genetic diversity, with genetically isolated populations, and a hotspot of genetic diversity that has a central role in the system's connectivity. Interestingly, they corresponded to the most recent and the oldest protected areas, respectively. This case study shows how moving from a "species pattern" perspective to an "eco-evolutionary processes" perspective can help assess and contribute to the effectiveness of biodiversity management plans. [ABSTRACT FROM AUTHOR]

Establishment of the coral–algal symbiosis begins during early ontogeny when juveniles acquire a mix of algae from their environment that often differs from the adults' algal assemblages. Despite the importance of the type of Symbiodiniaceae to this symbiosis, it is largely unknown how coral host identity and environment affect symbiosis establishment and is affected by the genetic composition of the symbionts. Here, we reciprocally transplanted planulae of the octocoral Rhytisma fulvum (Forskål, 1775) across depths and monitored the algal assemblages in the developing juveniles for 11 months. We then compared these to adult assemblages using ITS2 metabarcoding. Juveniles were consistently dominated by Symbiodinium, in addition to multiple Cladocopium species, which shifted in dominance with the juvenile age but maintained high similarity across depths. The type of Symbiodiniaceae environmentally available thus likely contributes to the algal symbionts that are initially acquired, while host identity may play a significant role in selecting for symbionts that are maintained during juvenile development. [ABSTRACT FROM AUTHOR]

As the major form of coral reef regime shift, stony coral to macroalgal transitions have received considerable attention. In the Caribbean, however, regime shifts in which scleractinian corals are replaced by octocoral assemblages hold potential for maintaining reef associated communities. Accordingly, forecasting the resilience of octocoral assemblages to future disturbance regimes is necessary to understand these assemblages' capacity to maintain reef biodiversity. We parameterised integral projection models quantifying the survival, growth, and recruitment of the octocorals, Antillogorgia americana, Gorgonia ventalina, and Eunicea flexuosa, in St John, US Virgin Islands, before, during, and after severe hurricane disturbance. Using these models, we forecast the density of populations of each species under varying future hurricane regimes. We demonstrate that although hurricanes reduce population growth, A. americana, G. ventalina, and E. flexuosa each display a capacity for quick recovery following storm disturbance. Despite this recovery potential, we illustrate how the population dynamics of each species correspond with a longer-term decline in their population densities. Despite their resilience to periodic physical disturbance events, ongoing global change jeopardises the future viability of octocoral assemblages. [ABSTRACT FROM AUTHOR]

Nearly all organisms must cope with parasitic infestation, and most research on parasite ecology in marine systems has focused on the variety of both direct and indirect impacts that parasites can have on hosts. In coral reef ecosystems, gnathiid isopods are one of the most common ectoparasites of fishes. For individuals infested with gnathiids, there is a heavy reliance on intraspecific mutualisms where specialist species groom or "clean" parasites off host fishes. However, gnathiids spend most of their time free-living and not associated with a host and are thus susceptible to consumption by non-cleaner fish species. Here, we investigated if non-cleaner and facultative (less specialized) cleaner fish consume ectoparasitic gnathiid isopods as often or in similar quantities as dedicated (highly specialized) cleaners. To do so, we sampled the gut contents of 797 fishes, representing 61 species and including both cleaner and non-cleaner fishes, to compare their consumption of gnathiid isopods. We found that although there is some site level variation, cleaner fishes eat significantly more gnathiids, and eat them more frequently, compared to non-cleaner fishes. Our results highlight the importance of both dedicated and facultative cleaners as consumers of ectoparasites and show that their role is unlikely to be supplanted by non-cleaner consumers. Furthermore, we suggest that different cleaner species act as complementary rather than redundant specialists. [ABSTRACT FROM AUTHOR]

We report the first documentation of in situ release of reproductive materials by female colonies of a soft coral, in this case Sclerophytum cf. heterospiculatum, from the subtropical island of Okinawa, Japan. Spawn release was observed on the nights of September 2 and 3, 2023 (two and three nights after the full moon). This observation widens our knowledge on the reproductive strategies of octocorals, providing insights into mechanisms of persistence of soft corals in marine ecosystems. [ABSTRACT FROM AUTHOR]

Characterizing patterns of genetic connectivity in marine species is of critical importance given the anthropogenic pressures placed on the marine environment. For sessile species, population connectivity can be shaped by many processes, such as pelagic larval duration, oceanographic boundaries and currents. This study combines restriction‐site associated DNA sequencing (RADseq) and passive particle dispersal modelling to delineate patterns of population connectivity in the pink sea fan, Eunicella verrucosa, a temperate octocoral. Individuals were sampled from 20 sites covering most of the species' northeast Atlantic range, and a site in the northwest Mediterranean Sea to inform on connectivity across the Atlantic‐Mediterranean transition. Using 7510 neutral SNPs, a geographic cline of genetic clusters was detected, partitioning into Ireland, Britain, France, Spain (Atlantic), and Portugal and Spain (Mediterranean). Evidence of significant inbreeding was detected at all sites, a finding not detected in a previous study of this species based on microsatellite loci. Genetic connectivity was characterized by an isolation by distance pattern (IBD) (r2 = 0.78, p < 0.001), which persisted across the Mediterranean‐Atlantic boundary. In contrast, exploration of ancestral population assignment using the program ADMIXTURE indicated genetic partitioning across the Bay of Biscay, which we suggest represents a natural break in the species' range, possibly linked to a lack of suitable habitat. As the pelagic larval duration (PLD) is unknown, passive particle dispersal simulations were run for 14 and 21 days. For both modelled PLDs, inter‐annual variations in particle trajectories suggested that in a long‐lived, sessile species, range‐wide IBD is driven by rare, longer dispersal events that act to maintain gene flow. These results suggest that oceanographic patterns may facilitate range‐wide stepping‐stone genetic connectivity in E. verrucosa and highlight that both oceanography and natural breaks in a species' range should be considered in the designation of ecologically coherent MPA networks. [ABSTRACT FROM AUTHOR]

We describe the complete mitogenomes of the black corals Alternatipathes mirabilis Opresko & Molodtsova, 2021 and Parantipathes larix (Esper, 1790) (Cnidaria, Anthozoa, Hexacorallia, Antipatharia, Schizopathidae). The analysed specimens include the holotype of Alternatipathes mirabilis, collected from Derickson Seamount (North Pacific Ocean; Gulf of Alaska) at 4,685 m depth and a potential topotype of Parantipathes larix, collected from Secca dei Candelieri (Mediterranean Sea; Tyrrhenian Sea; Salerno Gulf; Italy) at 131 m depth. We also assemble, annotate and make available nine additional black coral mitogenomes that were included in a recent phylogeny (Quattrini et al. 2023b), but not made easily accessible on GenBank. This is the first study to present and compare two mitogenomes from the same species of black coral (Stauropathes arctica (Lütken, 1871)) and, thus, place minimum boundaries on the expected level of intraspecific variation at the mitogenome level. We also compare interspecific variation at the mitogenome-level across five different specimens of Parantipathes Brook, 1889 (representing at least two different species) from the NE Atlantic and Mediterranean Sea. [ABSTRACT FROM AUTHOR]

Introduction: Host-parasite associations provide very useful models to study adaptive processes. We investigated the interaction between carnivorous marine gastropods, the Ovulidae or egg-cowries, and their cnidarian food targets. Ovulidae (Fleming, 1828), is a family of specialized carnivorous caenogastropods that feed by browsing on octocorals (Anthozoa: Octocorallia: Malacalcyonacea and Scleralcyonacea) or, to a much lesser degree, on antipatharians (Anthozoa: Hexacorallia: Antipatharia) and Stylasteridae (Hydrozoa: Hydroidolina: Anthoathecata). Very scanty information is available on the phylogenetic relationships and the degree of specificity of the relationship with the cnidarians of this corallivorous lineage, especially for deepwater taxa. Methods: To assess taxonomic identifications and investigate cnidarian/ovulid relationships in the context of their evolution, we generated an extensive molecular dataset comprising two mitochondrial (cox1 and 16S rDNA) and one nuclear gene (28S rDNA) from 524 specimens collected worldwide. The coral hosts of the ovulid species have been identified by integrating literature data with new records, employing morphological and/or molecular (the mitochondrial 16S rDNA and mtMSH, and the nuclear ITS2) markers. Results: We obtained a molecular phylogenetic framework for the Ovulidae, time-calibrated with nine reliable fossil records. An ancestral state reconstruction allowed to identify Hexacorallia or Hydroidolina as the most likely ancestral cnidarian host for the Ovulidae. Discussion: Our phylogenetic hypothesis revealed the existence of groups that do not completely correspond to the currently employed subfamilial arrangement. Concerning trophic ecology, while only pediculariines (Pedicularia and allied) are associated with hydrozoans (Stylasteridae), our results suggest that some ovulid lineages shifted independently between octocorals and hexacorals. [ABSTRACT FROM AUTHOR]

Coral reefs are biodiverse ecosystems that rely on trophodynamic transfers from primary producers to consumers through the detrital pathway. The sponge loop hypothesis proposes that sponges consume dissolved organic carbon (DOC) and produce large quantities of detritus on coral reefs, with this turn-over approaching the daily gross primary production of the reef ecosystem. In this study, we collected samples of detritus in the epilithic algal matrix (EAM) and samples from potential sources of detritus over two seasons from the forereef at Carrie Bow Cay, Belize. We chose this location to maximize the likelihood of finding support for the sponge loop hypothesis because Caribbean reefs have higher sponge abundances than other tropical reefs worldwide and the Mesoamerican barrier reef is an archetypal coral reef ecosystem. We used stable isotope analyses and eDNA metabarcoding to determine the composition of the detritus. We determined that the EAM detritus was derived from a variety of benthic and pelagic sources, with primary producers (micro- and macroalgae) as major contributors and metazoans (Arthropoda, Porifera, Cnidaria, Mollusca) as minor contributors. None of the sponge species that reportedly produce detritus were present in EAM detritus. The cnidarian signature in EAM detritus was dominated by octocorals, with a scarcity of hard corals. The composition of detritus also varied seasonally. The negligible contribution of sponges to reef detritus contrasts with the detrital pathway originally proposed in the sponge loop hypothesis. The findings indicate a mix of pelagic and benthic sources in the calmer summer and primarily benthic sources in the more turbulent spring. [ABSTRACT FROM AUTHOR]

Octocorals (Cnidaria: Anthozoa) have a global distribution and form benthic assemblages along the depth gradient, from shallow to deep waters. They often occur below SCUBA diving limits, where they can become dominant habitat builders and aggregate different taxa. During a cruise in February 2023, one octocoral specimen was collected at 1453 m depth at Kebrit Deep, in the northern Saudi Arabian Red Sea axis, an area with extremely high temperature and salinity profiles at depth. Morphological analysis coupled with DNA barcoding using two mitochondrial markers (COI and mtMuts), revealed that the coral belongs to Acanthogorgia, a genus of azooxanthellate octocorals known to occur from 3 to 2300 m depths in cold, temperate and tropical waters. In the Red Sea, the genus was previously only known from shallower waters. Hence, we report the deepest record of the genus Acanthogorgia from the warm and saline Red Sea basin. This finding provides novel insights on deepwater octocoral diversity in the Red Sea, a still scantily explored area of the world, while emphasizing the need for further explorations at depth. [ABSTRACT FROM AUTHOR]

A total of 10 specimens of Alcyonacea corals were collected at depths ranging from 905 m to 1 633 m by the manned submersible Shenhai Yongshi during two cruises in the South China Sea (SCS). Based on mitochondrial genomic characteristics, morphological examination, and sclerite scanning electron microscopy, the samples were categorized into four suborders (Calcaxonia, Holaxonia, Scleraxonia, and Stolonifera), and identified as 9 possible new cold-water coral species. Assessments of GC-skew dissimilarity, phylogenetic distance, and average nucleotide identity (ANI) revealed a slow evolutionary rate for the octocoral mitochondrial sequences. The nonsynonymous (Ka) to synonymous (Ks) substitution ratio (Ka/Ks) suggested that the 14 protein-coding genes (PCGs) were under purifying selection, likely due to specific deep-sea environmental pressures. Correlation analysis of the median Ka/Ks values of five gene families and environmental factors indicated that the genes encoding cytochrome b (cyt b) and DNA mismatch repair protein (mutS) may be influenced by environmental factors in the context of deep-sea species formation. This study highlights the slow evolutionary pace and adaptive mechanisms of deep-sea corals. [ABSTRACT FROM AUTHOR]

A new shrimp species of the genus Periclimenes is described based on specimens collected in the Bissagos Islands, Guinea-Bissau. Specimens were collected from an unidentified octocoral. This is the ninth species in the genus known to be from the East Atlantic and Mediterranean. [ABSTRACT FROM AUTHOR]

Octocorals represent a major alternative group in the benthic community of reefs that have diverged from hexacoral dominance. Despite their phototrophic symbionts, supplementing their diet with heterotrophic sources may promote their growth, particularly when compared to hexacorals in bleaching conditions. However, limited comprehensive data exists on octocorals' trophic ecology, especially regarding their ability to feed on dissolved organic matter (DOM), which comprises the largest pool of organic matter in reefs. This study aims to investigate the ability of two octocorals (Sarcophyton glaucum and Lobophytum sp.) to feed on DOM and compare this ability to that of hexacorals, such as Stylophora pistillata and Turbinaria reniformis. The study measured the net fluxes of DOM under varying DOM concentrations and under heat stress. The results demonstrate that all coral species were net producers of DOM at ambient concentrations, but became net consumers once seawater was supplemented with DOM. Furthermore, our study highlights a relationship between coral physiological responses to heat stress and DOM uptake. Corals that increased (S. pistillata) or maintained (S. glaucum and Lobophytum sp.) their DOM uptake rates at high temperature were the most resilient to heat stress. In contrast, T. reniformis exhibited lower DOM uptake rates at high temperatures, which was associated with significant bleaching. Understanding the ability of corals to feed on DOM may, therefore, provide insight into the resilience of species under ocean warming conditions. [ABSTRACT FROM AUTHOR]

A new species and genus of stem-group 'soft corals' (Anthozoa: Octocorallia: Alcyonacea) is described and illustrated in detail, as well as compared to other species of the sparse octocorallian fossil record. Sueciatractos leipnitzae gen. et sp. nov. has been collected from the Upper Silurian Hemse beds of the Isle of Gotland, Sweden. The new taxon differs from all other taxa by its unique form of sclerites which were fused at first glance, but stacked compactly, densely packed aggregates forming a nearly solid skeleton or former supporting layers in part. Sueciatractos is compared with other fossil octocoral species that were known by microscopic/mesoscopic sclerites. [ABSTRACT FROM AUTHOR]

Nanipora Miyazaki & Reimer, 2015 is a recently described monotypic octocoral genus belonging to the family Helioporidae (class Octocorallia). Nanipora kamurai Miyazaki & Reimer, 2015 was formally described from shallow coral reefs around Zamami Island, within Kerama-shoto National Park, in Okinawa Prefecture, southern Japan. To date, Nanipora has been reported from two other locations in Japan: N. aff. kamurai from a shallow inner lagoon at Iriomotejima Island, and Nanipora cf. kamurai from the coral reef surrounding a shallow CO2 vent at Iotorishima Island, both in Okinawa Prefecture. Additionally, Nanipora cf. kamurai has been reported from three locations outside Japan: in shallow seagrass meadows at Dongsha Atoll in the South China Sea, on coral reefs at Koh Tao in Thailand and from a reef in Toboso, central Philippines. Finally, N. kamurai has been detected in environmental DNA samples from the Rowley Shoals off northwestern Australia. As a ‘living fossil’ and also apparently common in the low pH environment of Iotorishima I., a clearer understanding of the distribution of the genus should aid in better understanding of its ecology. Here, we report three new additional records from the Ryukyu Archipelago where Nanipora colonies were found, resulting in ten total records of Nanipora. Molecular phylogenetic analyses utilizing cytochrome oxidase subunit I (COI), mitochondrial mismatch repair protein (mtMutS), and the internal transcribed spacer region (ITS) sequences of specimens from two of these new locations combined with additional sequences from previously collected specimens from Dongsha, Iotorishima, and Iriomotejima showed evidence of three closely related groups within Nanipora, warranting future investigations into the species diversity of this genus. [ABSTRACT FROM AUTHOR]

Scientific surveys employing remotely operated vehicles (ROVs) provide valuable imagery for identifying Vulnerable Marine Ecosystems (VMEs). However, there is presently no established framework for distinguishing VMEs from these images. While existing guidelines effectively address certain habitat types, such as scleractinian reefs, dense octocoral gardens, and chemosynthetic ecosystems, achieving consensus becomes more challenging for other habitats. Our investigation centered on two key localized rocky outcrops on the Uruguayan shelf, conducting ROV dives to explore these environments. This study aims to evaluate initial global consensus guidelines for VME identification from imagery and discuss the suitability of these criteria, and report the existence of Hard Bottom Soft Coral Gardens and Sponge associations in the inner Uruguayan shelf. Recognizing these habitats is of utmost importance for the Uruguayan government, which has expressed the intent to safeguard ecologically representative and well-connected systems crucial for marine biodiversity.

Octocorals (Cnidaria: Anthozoa) have a global distribution and form benthic assemblages along the depth gradient, from shallow to deep waters. They often occur below SCUBA diving limits, where they can become dominant habitat builders and aggregate different taxa. During a cruise in February 2023, one octocoral specimen was collected at 1453 m depth at Kebrit Deep, in the northern Saudi Arabian Red Sea axis, an area with extremely high temperature and salinity profiles at depth. Morphological analysis coupled with DNA barcoding using two mitochondrial markers (COI and mtMuts), revealed that the coral belongs to Acanthogorgia, a genus of azooxanthellate octocorals known to occur from 3 to 2300 m depths in cold, temperate and tropical waters. In the Red Sea, the genus was previously only known from shallower waters. Hence, we report the deepest record of the genus Acanthogorgia from the warm and saline Red Sea basin. This finding provides novel insights on deep-water octocoral diversity in the Red Sea, a still scantily explored area of the world, while emphasizing the need for further explorations at depth.

Unlike reef-building, scleractinian corals, Caribbean soft corals (octocorals) have not suffered marked declines in abundance associated with anthropogenic ocean warming. Both octocorals and reef-building scleractinians depend on a nutritional symbiosis with single-celled algae living within their tissues. In both groups, increased ocean temperatures can induce symbiont loss (bleaching) and coral death. Multiple heat waves from 2014 to 2016 resulted in widespread damage to reef ecosystems and provided an opportunity to examine the bleaching response of three Caribbean octocoral species. Symbiont densities declined during the heat waves but recovered quickly, and colony mortality was low. The dominant symbiont genotypes within a host generally did not change, and all colonies hosted symbiont species in the genus Breviolum. Their association with thermally tolerant symbionts likely contributes to the octocoral holobiont's resistance to mortality and the resilience of their symbiont populations. The resistance and resilience of Caribbean octocorals offer clues for the future of coral reefs. [ABSTRACT FROM AUTHOR]

Pink pigmentation on massive corals is quite commonly observed in the global reefs, but its function on the surface area of corals is less understood. In the present study, the coral video transect method was employed to document the incidence of pink pigmentation on Porites colonies from 21 islands under the Gulf of Mannar Marine Biosphere Reserve (GoMMBR), India. Results revealed that 19% (n = 77 out of 517) of Porites sp. colonies displayed pink pigmentation as a stress indicator in response to the colonization of epibionts. Porites colonies exhibited pink pigmentation when infected with epibionts like a vermetid snail, Ceraesignum sp. (12%; n = 49), a rhodolith, Hydrolithon sp. (5%; n = 21), or both (2%; n = 7). This study indicates that Porites pink pigment deposition aids in minimizing surface tissue area damage by preventing further progression of infesting agents such as vermitid snails and rhodoliths on the surface areas of corals. [ABSTRACT FROM AUTHOR]

The habitat-forming Endangered 'cauliflower' soft coral Dendronephthya australis, endemic to South-east Australia, is in rapid decline. To aid future conservation strategies, it is vital to understand the fundamental biological processes of this species, particularly reproduction. This study describes the first records of sexual reproduction and asexual clonal replication, with observations both in aquaria and in the wild. We used a combination of observations including histological analyses of fresh specimens, and images of colonies in situ taken over 19 years, to investigate the reproductive cycle of D. australis. Mature oocytes and spermaries were found to develop within colonies during February/March, 2022. We subsequently closed the life cycle of D. australis from colonies spawned in aquaria, documenting all stages of embryogenesis and larval development through to polyp metamorphosis, and successfully transplanted juvenile colonies back into the field and documented their growth over six months to a maximum 435 polyps in size. We also document autonomous fragmentation events to provide accounts of asexual clonal propagation. These records confirm that D. australis is gonochoric and likely a broadcast spawning species that is also capable of utilising asexual reproduction by clonal replication. Observations of mature gametes support the hypothesis that spawning activity coincides with the seasonal increase in water temperature, and is likely to be a continuous phenomenon over 5 months of the year (November–March). These observations not only contribute to the knowledge base for this species, but also provide invaluable information on reproductive strategies that will support conservation efforts to assist the recovery of D. australis populations. [ABSTRACT FROM AUTHOR]

The deep-sea precious red coral Hemicorallium laauense has long been overharvested in the North Pacific for the jewelry and curio trades. An understanding of the population structure and connectivity of these octocorals has been limited due to the difficulty of sampling and taxonomic challenges within the Family Coralliidae. We report on population genetics of 270 H. laauense individuals from 16 populations throughout the Main Hawaiian Islands (MHI) and the Northwestern Hawaiian Islands (NWHI) using nine microsatellite loci. Observed heterozygosity (0.69–0.85) was generally lower than expected heterozygosity (0.71–0.85) except for the population at Twin Banks. Moderate FIS values (0.01–0.20) were present in nearly half of the populations. Global G'ST (0.166) and pairwise values were moderate to high (– 0.003 to 0.489). G'ST values also show moderate genetic structuring among populations within seamounts (0.12–0.22) for populations separated by as little as 3 km. DAPC indicated separation of the MHI from the NWHI, but two NWHI sites fall into the MHI clusters and samples from Ka'ena Point (an MHI site) appear to form their own cluster. Membership assignments showed moderate admixture between some locations, while three locations showed almost no admixture. Within-seamount admixture was surprisingly limited for populations on the same seamount. A pattern of isolation by distance, with exchange primarily among adjacent seamounts, was supported by MIGRATE results but not by Mantel tests. These results suggest a mixed pattern of connectivity, with some distant locations well connected and others more isolated. The inconsistent connectivity of these corals is likely amplified by their patchy distributions. [ABSTRACT FROM AUTHOR]

This research provides an extensive analysis of the biodiversity and distribution patterns of copepod crustaceans associated with octocoral species. A comprehensive dataset comprising 966 records pertaining to 233 copepod species, encompassing 54 genera, 18 families, and 3 orders, was compiled from 92 scientific papers published between 1858 and 2023, and updated as open data to GBIF. These copepods were found to be closely associated with 183 octocoral species, representing 72 genera and 28 families. The analysis revealed a total of 393 distinct interspecific associations between copepods, classified under the orders Cyclopoida, Harpacticoida, and Siphonostomatoida, and diverse octocorals. Approximately 60% of these associations were reported only once in the literature, which poses challenges to assessing the level of host specificity among the majority of copepod species linked with octocorals. Notably, over 91% of the recorded copepod species were found at depths not exceeding 30 m, with only four copepod species reported at greater depths surpassing 500 m. The presence of these symbiotic copepods was documented across 215 sampling sites situated within 8 of the 12 defined marine ecoregions, with particular attention to the Western Indo-Pacific, Central Indo-Pacific, and Temperate Northern regions. Despite the comprehensive examination of available data, this study highlights substantial gaps in our comprehension of copepod crustacean diversity and distribution in association with octocorals. Moreover, crucial information concerning symbiotic copepods is conspicuously absent for approximately 94% of potential octocoral host species. These disparities emphasize the imperative need for further scientific inquiry to unveil the intricacies of symbiotic relationships and to contribute to a more holistic understanding of copepod–octocoral associations. [ABSTRACT FROM AUTHOR]