Search

ABSTRACT Aim Location Methods Results Main Conclusions Determining the species distribution and factors shaping it is a major challenge for conservation planning. Ecological niche models (ENMs) facilitate the comprehension of how environmental factors may influence species occurrence, providing spatially explicit information relevant to conservation. Therefore, our aim was to estimate the potential distribution of key habitat‐forming Mediterranean gorgonians, whose conservation would protect many co‐occurring species.Mediterranean Sea.We modelled the potential distribution of the Mediterranean gorgonians Eunicella singularis, Eunicella cavolini, Paramuricea clavata and Corallium rubrum, using an ensemble ENM that combines nine algorithms. An extensive dataset of presence records (> 4378) collected through scientific surveys and citizen‐science was intersected with oceanographic and topographic information within the coralligenous habitat depth range (< 150 m). This approach was used to map the habitat suitability of the study area for each species, assess related uncertainty, identify the most important factors shaping their distribution, and evaluate the overlap with the current network of Marine Protected Areas.The model identified higher habitat suitability for the occurrence of each gorgonian species in the NW Mediterranean, with roughness and temperature as the main drivers of their distribution. Conversely, the poorly sampled SE Mediterranean showed low habitat suitability, although there is a greater uncertainty associated with this estimate. The combined potential distribution of the four species is estimated to cover a quarter of Mediterranean shallow and mesophotic waters, but only 19% was included within protected areas.The habitat suitability and uncertainty maps provide a valuable tool for the conservation and management of Mediterranean gorgonian species by offering spatially explicit information critical for marine spatial planning. The model estimates of habitat suitability showed low uncertainty for most of the study area, with few exceptions in the SE Mediterranean. Further studies, particularly in the SE Mediterranean will contribute to validate these results and will provide new information to improve future modelling efforts. [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]

BackgroundThe role of bacterial symbionts that populate octocorals (Cnidaria, Octocorallia) is still poorly understood. To shed light on their metabolic capacities, we examined 66 high-quality metagenome-assembled genomes (MAGs) spanning 30 prokaryotic species, retrieved from microbial metagenomes of three octocoral species and seawater.ResultsSymbionts of healthy octocorals were affiliated with the taxa Endozoicomonadaceae, Candidatus Thioglobaceae, Metamycoplasmataceae, unclassified Pseudomonadales, Rhodobacteraceae, unclassified Alphaproteobacteria and Ca. Rhabdochlamydiaceae. Phylogenomics inference revealed that the Endozoicomonadaceae symbionts uncovered here represent two species of a novel genus unique to temperate octocorals, here denoted Ca. Gorgonimonas eunicellae and Ca. Gorgonimonas leptogorgiae. Their genomes revealed metabolic capacities to thrive under suboxic conditions and high gene copy numbers of serine-threonine protein kinases, type 3-secretion system, type-4 pili, and ankyrin-repeat proteins, suggesting excellent capabilities to colonize, aggregate, and persist inside their host. Contrarily, MAGs obtained from seawater frequently lacked symbiosis-related genes. All Endozoicomonadaceae symbionts harbored endo-chitinase and chitin-binging protein-encoding genes, indicating that they can hydrolyze the most abundant polysaccharide in the oceans. Other symbionts, including Metamycoplasmataceae and Ca. Thioglobaceae, may assimilate the smaller chitin oligosaccharides resulting from chitin breakdown and engage in chitin deacetylation, respectively, suggesting possibilities for substrate cross-feeding and a role for the coral microbiome in overall chitin turnover. We also observed sharp differences in secondary metabolite production potential between symbiotic lineages. Specific Proteobacteria taxa may specialize in chemical defense and guard other symbionts, including Endozoicomonadaceae, which lack such capacity.ConclusionThis is the first study to recover MAGs from dominant symbionts of octocorals, including those of so-far unculturable Endozoicomonadaceae, Ca. Thioglobaceae and Metamycoplasmataceae symbionts. We identify a thus-far unanticipated, global role for Endozoicomonadaceae symbionts of corals in the processing of chitin, the most abundant natural polysaccharide in the oceans and major component of the natural zoo- and phytoplankton feed of octocorals. We conclude that niche partitioning, metabolic specialization, and adaptation to low oxygen conditions among prokaryotic symbionts likely contribute to the plasticity and adaptability of the octocoral holobiont in changing marine environments. These findings bear implications not only for our understanding of symbiotic relationships in the marine realm but also for the functioning of benthic ecosystems at large. Video Abstract.

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]

Octocorals are extremely important animals for forming coral reefs and maintaining life in the marine environment and are widely distributed. The focus species Plexaurella grandiflora is an endemic species from Brazil. It is subject to the most varied external stressors, from ocean surface warming, pollution, damage caused by tourism, and predation by other animals. In this sense, the present study aimed to survey the population characteristics of P. grandiflora in a shallow tropical reef in northeast Brazil. Furthermore, we evaluated the stress and damage caused by coral-eating gastropods of the Muricidae family, found associated with colony structure. Through free dives between the years 2016 and 2017, 143 colonies of P. grandiflora were marked and observed, and they were analyzed in their size, supporting substrate, distribution, presence of damage, and impact by coral-eating gastropods. The cataloged colonies were larger than those recognized in the literature and were distributed in aggregate. A total of 85 gastropods of two species (Coralliophila aberrans and Coralliophila salebrosa) were recorded preying on gorgonians. The damage ranged from light to deep, from polyp removal to exposure of the protein axis. Predation occurred predominantly at the base of the colonies. As it is an endemic species and in need of studies, this study warns of the need for studies focused on the ecology and conservation of this gorgonian and its critical habitats. [ABSTRACT FROM AUTHOR]

Barnacles of the genus Conopea are obligate epibionts of gorgonians and antipatharians. The species Conopea saotomensis Carrison-Stone et al. 2013 , previously only known from the islands of São Tomé and Príncipe and the coast of Gabon, is reported from the Bijagós archipelago, Guinea-Bissau, based on morphological examination and DNA barcoding of specimens. The new record extends the known range of the species about 3000 km to the northwest. [ABSTRACT FROM AUTHOR]

BackgroundIn octocorals (Cnidaria Octocorallia), the functional relationship between host health and its symbiotic consortium has yet to be determined. Here, we employed comparative metagenomics to uncover the distinct functional and phylogenetic features of the microbiomes of healthy Eunicella gazella, Eunicella verrucosa, and Leptogorgia sarmentosa tissues, in contrast with the microbiomes found in seawater and sediments. We further explored how the octocoral microbiome shifts to a pathobiome state in E. gazella.ResultsMultivariate analyses based on 16S rRNA genes, Clusters of Orthologous Groups of proteins (COGs), Protein families (Pfams), and secondary metabolite-biosynthetic gene clusters annotated from 20 Illumina-sequenced metagenomes each revealed separate clustering of the prokaryotic communities of healthy tissue samples of the three octocoral species from those of necrotic E. gazella tissue and surrounding environments. While the healthy octocoral microbiome was distinguished by so-far uncultivated Endozoicomonadaceae, Oceanospirillales, and Alteromonadales phylotypes in all host species, a pronounced increase of Flavobacteriaceae and Alphaproteobacteria, originating from seawater, was observed in necrotic E. gazella tissue. Increased abundances of eukaryotic-like proteins, exonucleases, restriction endonucleases, CRISPR/Cas proteins, and genes encoding for heat-shock proteins, inorganic ion transport, and iron storage distinguished the prokaryotic communities of healthy octocoral tissue regardless of the host species. An increase of arginase and nitric oxide reductase genes, observed in necrotic E. gazella tissues, suggests the existence of a mechanism for suppression of nitrite oxide production by which octocoral pathogens may overcome the host's immune system.ConclusionsThis is the first study to employ primer-less, shotgun metagenome sequencing to unveil the taxonomic, functional, and secondary metabolism features of prokaryotic communities in octocorals. Our analyses reveal that the octocoral microbiome is distinct from those of the environmental surroundings, is host genus (but not species) specific, and undergoes large, complex structural changes in the transition to the dysbiotic state. Host-symbiont recognition, abiotic-stress response, micronutrient acquisition, and an antiviral defense arsenal comprising multiple restriction endonucleases, CRISPR/Cas systems, and phage lysogenization regulators are signatures of prokaryotic communities in octocorals. We argue that these features collectively contribute to the stabilization of symbiosis in the octocoral holobiont and constitute beneficial traits that can guide future studies on coral reef conservation and microbiome therapy. Video Abstract.

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.

Global warming of the oceans poses a double threat to benthic organisms as they reach their thermal limits and starve to death due to declines in plankton abundance during heat waves. Under these circumstances, dissolved nutrients become an important alternative food source, especially in temperate regions where they can reach high concentrations. Although octocorals play a central role in temperate Marine Animal Forests and benthic-pelagic coupling, our knowledge of their feeding ecology is still limited. We used 13C and 15N isotope labeling to investigate feeding rates on dissolved inorganic (carbon, ammonium, nitrate) and organic (urea, amino acids) nutrients of the two most common Mediterranean gorgonians, the mixotrophic species Eunicella singularis and the heterotrophic species Paramuricea clavata. We also measured the uptake of natural dissolved organic matter (DOM) provided at different concentrations. Measurements were conducted at 17°C and 24°C to anticipate the effects of ocean warming. Our findings indicate that gorgonians exhibit notably low uptake rates of dissolved inorganic and organic nutrients, both at 17°C and 24°C. At 24°C, gorgonians experienced heat stress, as evidenced by elevated respiration rates, the loss of symbionts in E. singularis, and decreased lipid reserves in P. clavata. However, we did not observe a significant increase in the uptake rates of dissolved inorganic or organic nutrients, except for dissolved organic carbon in E. singularis. This study provides valuable insight into the nutritional requirements of temperate octocorals. The results demonstrate that dissolved nutrients, in particular nitrogen, do not play a substantial role in the diet of gorgonians, suggesting that these organisms primarily rely on the capture of plankton and detrital material for their nitrogen requirements. Therefore, temperate octocorals may be at high risk of severe starvation in the future.

Mass mortality events and anthropogenic impacts affecting Paramuricea clavata (Risso, 1826) have been increasingly documented during the last decades. These impacts have enhanced the settling of epibiont organisms on injured colonies. This epibiosis was studied using photographic sampling carried out on the granitic outcrops of the Tavolara Channel within the Tavolara–Punta Coda Cavallo marine-protected area (NE Sardinia) between 2017 and 2023 at 35–55 m. The number of colonies and percentage of surface involved in the epibiosis, the specific richness of the epibiont community, and the temporal evolution of the phenomenon were studied. Almost all the investigated gorgonians (93%) showed parts involved in epibiosis, with high percentages of surface covering (one-third of the surface). Out of the 37 epibiont species recorded, the most recurrent ones demonstrated an ecological succession dominated by Hydrozoa, Porifera, Bryozoa, Serpulidae, and the parasitic soft coral Alcyomiun coralloides. Nevertheless, single colonies studied over time revealed the unpredictability of the colonization process. The peculiar habitat of the granitic outcrops hosting the P. clavata forests is of a high naturalistic value and demonstrates a widespread condition of suffering, supported by both environmental and anthropogenic sources of stress. Such considerations make it necessary to review the current zonation of the area, where the actual vulnerability and usability evaluations are based on incomplete information. [ABSTRACT FROM AUTHOR]

Despite the current decline of scleractinian coral populations, octocorals are thriving on reefs in the Caribbean Sea and western North Atlantic Ocean. These cnidarians are holobiont entities, interacting with a diverse array of microorganisms. Few studies have investigated the spatial and temporal stability of the bacterial communities associated with octocoral species and information regarding the co-occurrence and potential interactions between specific members of these bacterial communities remain sparse. To address this knowledge gap, this study investigated the stability of the bacterial assemblages associated with two common Caribbean octocoral species, Eunicea flexuosa and Antillogorgia americana, across time and geographical locations and performed network analyses to investigate potential bacterial interactions. Results demonstrated that general inferences regarding the spatial and temporal stability of octocoral-associated bacterial communities should not be made, as host-specific characteristics may influence these factors. In addition, network analyses revealed differences in the complexity of the interactions between bacteria among the octocoral species analyzed, while highlighting the presence of genera known to produce bioactive secondary metabolites in both octocorals that may play fundamental roles in structuring the octocoral-associated bacteriome. [ABSTRACT FROM AUTHOR]

Abstract Background The role of bacterial symbionts that populate octocorals (Cnidaria, Octocorallia) is still poorly understood. To shed light on their metabolic capacities, we examined 66 high-quality metagenome-assembled genomes (MAGs) spanning 30 prokaryotic species, retrieved from microbial metagenomes of three octocoral species and seawater. Results Symbionts of healthy octocorals were affiliated with the taxa Endozoicomonadaceae, Candidatus Thioglobaceae, Metamycoplasmataceae, unclassified Pseudomonadales, Rhodobacteraceae, unclassified Alphaproteobacteria and Ca. Rhabdochlamydiaceae. Phylogenomics inference revealed that the Endozoicomonadaceae symbionts uncovered here represent two species of a novel genus unique to temperate octocorals, here denoted Ca. Gorgonimonas eunicellae and Ca. Gorgonimonas leptogorgiae. Their genomes revealed metabolic capacities to thrive under suboxic conditions and high gene copy numbers of serine-threonine protein kinases, type 3-secretion system, type-4 pili, and ankyrin-repeat proteins, suggesting excellent capabilities to colonize, aggregate, and persist inside their host. Contrarily, MAGs obtained from seawater frequently lacked symbiosis-related genes. All Endozoicomonadaceae symbionts harbored endo-chitinase and chitin-binging protein-encoding genes, indicating that they can hydrolyze the most abundant polysaccharide in the oceans. Other symbionts, including Metamycoplasmataceae and Ca. Thioglobaceae, may assimilate the smaller chitin oligosaccharides resulting from chitin breakdown and engage in chitin deacetylation, respectively, suggesting possibilities for substrate cross-feeding and a role for the coral microbiome in overall chitin turnover. We also observed sharp differences in secondary metabolite production potential between symbiotic lineages. Specific Proteobacteria taxa may specialize in chemical defense and guard other symbionts, including Endozoicomonadaceae, which lack such capacity. Conclusion This is the first study to recover MAGs from dominant symbionts of octocorals, including those of so-far unculturable Endozoicomonadaceae, Ca. Thioglobaceae and Metamycoplasmataceae symbionts. We identify a thus-far unanticipated, global role for Endozoicomonadaceae symbionts of corals in the processing of chitin, the most abundant natural polysaccharide in the oceans and major component of the natural zoo- and phytoplankton feed of octocorals. We conclude that niche partitioning, metabolic specialization, and adaptation to low oxygen conditions among prokaryotic symbionts likely contribute to the plasticity and adaptability of the octocoral holobiont in changing marine environments. These findings bear implications not only for our understanding of symbiotic relationships in the marine realm but also for the functioning of benthic ecosystems at large. Video Abstract

Distribution and occurrence data of the sea fan Leptogorgia sarmentosa (Esper, 1791) in the Mediterranean Sea were updated thanks to new photographic surveys, highlighting the presence of the species off NE Sardinia and, in particular, in the Tavolara-Punta Coda Cavallo Marine Protected Area (TPCCMPA). The estimated average distance among colonies strongly suggests that they are not able to sexually reproduce and that they probably can be considered a sterile pseudo-population supported by inputs of larvae from the Italian mainland coast towards Sardinia. The putative conveyor belt for larval input to this area is a small permanent gyre (the North-Tyrrhenian Gyre) counterclockwise moving from the Italian to the Sardinian coasts. In TPCCMPA, the growth of one colony settled at 30 m depth was investigated across 7 years (2016–2022). The morphometric parameters indicated a linear development of the colony, in terms of branch development and 3D complexity estimated through the fractal dimension. The observed growth rates were not regular but were reached through a highly variable positive and negative oscillation. A significant correlation was obtained between growth rate and average Autumn and Winter water temperature, suggesting that somatic growth occurs in these periods. In the context of long-lasting elevated seawater temperatures and local damage linked to fishing activities, L. sarmentosa was confirmed to be a resilient species compared with other erect seascape components, like other gorgonians and sponges. [ABSTRACT FROM AUTHOR]

The frequency and severity of marine heatwaves causing mass mortality events in tropical and temperate coral species increases every year, with serious consequences on the stability and resilience of coral populations. Although recovery and persistence of coral populations after stress events is closely related to adult fitness, as well as larval survival and settlement, much remains unknown about the effects of thermal stress on early life‐history stages of temperate coral species. In the present study, the reproductive phenology and the effect of increased water temperature (+4°C and +6°C above ambient, 20°C) on larval survival and settlement was evaluated for two of the most representative Mediterranean octocoral species (Eunicella singularis and Corallium rubrum). Our study shows that reproductive behavior is more variable than previously reported and breeding period occurs over a longer period in both species. Thermal stress did not affect the survival of symbiotic E. singularis larvae but drastically reduced the survival of the non‐symbiotic C. rubrum larvae. Results on larval biomass and caloric consumption suggest that higher mortality rates of C. rubrum exposed to increased temperature were not related to depletion of endogenous energy in larvae. The results also show that settlement rates of E. singularis did not change in response to elevated temperature after 20 days of exposure, but larvae may settle fast and close to their native population at 26°C (+6°C). Although previous experimental studies found that adult colonies of both octocoral species are mostly resistant to thermal stress, our results on early life‐history stages suggest that the persistence and inter‐connectivity of local populations may be severely compromised under continued trends in ocean warming. [ABSTRACT FROM AUTHOR]

Caribbean scleractinian corals have been declining in recent decades while octocorals appear to be thriving. Although microbial communities associated with scleractinians have been extensively studied, less is known about octocoral-associated communities. To investigate whether octocoral-associated microorganisms can provide resistance against coral pathogens, bacteria from the mucus and external surfaces of three common Caribbean octocoral species (Gorgonia ventalina, Eunicea flexuosa, and Antillogorgia americana) were isolated. Isolates were tested for bioactivity against six scleractinian coral pathogens at three temperatures to capture potential differences under varying conditions. Production of bioactive metabolites was evaluated using disk diffusion assays while growth competition assays determined whether the pathogen and isolate could establish simultaneously. Over half of the isolates, members of the phyla Actinobacteria, Firmicutes and Proteobacteria, produced compounds that inhibited the growth of one or more pathogens with some variation in bioactivity noted across temperatures. When inoculated simultaneously, most isolates were able to grow in presence of the pathogens while temperature did not have a significant impact. Collectively, these results demonstrate that octocorals support a diverse group of culturable bacteria capable of competing against coral pathogens. The putative protective roles of these bacteria provide insight into why Caribbean octocorals may be less susceptible to diseases and might explain their increasing prevalence on degraded reefs. [ABSTRACT FROM AUTHOR]

Trophic niche theory predicts that species in competition for a limiting resource will evolve adaptations allowing them to consume alternative resources and occupy new niche space. Trophic niche partitioning is often identified by differences in the morphology of feeding structures across species; however, these differences may not always be readily observable. Due to their constrained polyp morphology, octocorals are often viewed a single functional group that contributes to benthic-pelagic coupling by feeding opportunistically on available particles. To test the hypothesis that sympatric gorgonians share the same trophic niche, feeding selectivity of three gorgonian species (Leptogorgia virgulata, Muricea pendula, and Thesea nivea) was compared using a combination of flume experiments and stable isotope analysis. The tentacle length and polyp surface area of L. virgulata and T. nivea were also measured and compared. In flume experiments, clearance of rotifers ("typical" zooplankton) and a mixture of cultured phytoplankton indicated that L. virgulata and T. nivea fed on zooplankton and not phytoplankton. Stable isotope values for all three species are consistent with distinct trophic niches, with M. pendula occupying a lower trophic level. Thesea nivea was found to have significantly larger polyp surface area and tentacle length; however, this did not appear to explain observed trophic differences. The results of this study provide evidence for niche partitioning, but future work is required to better understand the mechanism behind this divergence. [ABSTRACT FROM AUTHOR]

Abstract Background In octocorals (Cnidaria Octocorallia), the functional relationship between host health and its symbiotic consortium has yet to be determined. Here, we employed comparative metagenomics to uncover the distinct functional and phylogenetic features of the microbiomes of healthy Eunicella gazella, Eunicella verrucosa, and Leptogorgia sarmentosa tissues, in contrast with the microbiomes found in seawater and sediments. We further explored how the octocoral microbiome shifts to a pathobiome state in E. gazella. Results Multivariate analyses based on 16S rRNA genes, Clusters of Orthologous Groups of proteins (COGs), Protein families (Pfams), and secondary metabolite-biosynthetic gene clusters annotated from 20 Illumina-sequenced metagenomes each revealed separate clustering of the prokaryotic communities of healthy tissue samples of the three octocoral species from those of necrotic E. gazella tissue and surrounding environments. While the healthy octocoral microbiome was distinguished by so-far uncultivated Endozoicomonadaceae, Oceanospirillales, and Alteromonadales phylotypes in all host species, a pronounced increase of Flavobacteriaceae and Alphaproteobacteria, originating from seawater, was observed in necrotic E. gazella tissue. Increased abundances of eukaryotic-like proteins, exonucleases, restriction endonucleases, CRISPR/Cas proteins, and genes encoding for heat-shock proteins, inorganic ion transport, and iron storage distinguished the prokaryotic communities of healthy octocoral tissue regardless of the host species. An increase of arginase and nitric oxide reductase genes, observed in necrotic E. gazella tissues, suggests the existence of a mechanism for suppression of nitrite oxide production by which octocoral pathogens may overcome the host’s immune system. Conclusions This is the first study to employ primer-less, shotgun metagenome sequencing to unveil the taxonomic, functional, and secondary metabolism features of prokaryotic communities in octocorals. Our analyses reveal that the octocoral microbiome is distinct from those of the environmental surroundings, is host genus (but not species) specific, and undergoes large, complex structural changes in the transition to the dysbiotic state. Host-symbiont recognition, abiotic-stress response, micronutrient acquisition, and an antiviral defense arsenal comprising multiple restriction endonucleases, CRISPR/Cas systems, and phage lysogenization regulators are signatures of prokaryotic communities in octocorals. We argue that these features collectively contribute to the stabilization of symbiosis in the octocoral holobiont and constitute beneficial traits that can guide future studies on coral reef conservation and microbiome therapy. Video Abstract

Among Mediterranean habitat-forming alcyonaceans, the sea fan Eunicella verrucosa is known to form dense forests at circalittoral depths, providing seascape complexity and sustaining a rich associated fauna. Its occurrence in the Tavolara–Punta Coda Cavallo Marine Protected Area (NE Sardinia) has never been deeply investigated despite this area being well known from a biocoenotic point of view. This study provides new information on the size of the colonies settled between 35 and 59 m depth on granitic outcrops and represents a contribution to highlighting the hotspot of megabenthic diversity enclosed in the protected area. The presence of 100 colonies was assessed by photographic samplings performed between 2015 and 2020, in a small area characterized by peculiar ecological conditions. The morphometric descriptions and age estimation showed a persistently isolated population probably derived from a stochastic event of settling of larvae presumably coming from the Tuscany Archipelago. A richly associated epibiotic community, composed of 18 species/OTUs, showed how branched bryozoans, particularly Turbicellepora avicularis, and the parasitic octocoral Alcyonium coralloides, affected the colonies' branches, suggesting a putative anthropogenic impact related to fishing activity. This study indicates that proper protection and management strategies are mandatory for the Marine Protected Area, in order to conserve this unique population and the whole associated benthic assemblage. [ABSTRACT FROM AUTHOR]

Octocorals are relatively understudied than other coral reef organisms despite their ecological and economic values. The Philippines is known to have high marine biodiversity, but information on octocorals is lacking. This study investigated spatial and temporal variations in the assemblage of octocorals in selected reef sites in the West Philippine Sea (WPS)- the Kalayaan Island Group (i.e., Pag-asa, Sabina, Lawak, and Northeast Investigator) and Ulugan in 2017 and 2019. Results showed high octocoral taxonomic richness (at least 10 families) in the study sites. Mean percent octocoral cover in WPS was 5.35% SE ± 0.55, with Sabina having the highest octocoral cover in both years. Significant differences in octocoral cover were observed among sites in both years, but among-station differences were only observed in 2017. Octocoral assemblage also differed among sites in both years (ANOSIM: R > 0.5, p < 0.05), wherein different octocoral taxa dominated in different sites. In particular, variations were driven by high cover of holaxonians, nephtheids, and coelogorgiids in Sabina, and clavulariids, tubiporiids, and xeniids in Northeast Investigator in 2017. In 2019, significant variations were driven by high cover of helioporiids in Pag-asa, while Sabina had higher abundance of holaxonians, nephtheids, alcyoniids, and xeniids. Short-term temporal variation on octocoral cover in monitoring stations in Pag-asa was not observed (Kruskal-Wallis, p > 0.05), although the overall mean octocoral cover increased from 1.23% ± SE 0.47 in 2017 to 2.09% SE ± 0.37 in 2019. Further, there was no significant change in the octocoral assemblage in Pag-asa between years (ANOSIM, R = 0.11, p = 0.07). This study highlights high octocoral taxonomic richness in the WPS relative to other sites in the Indo-Pacific Region and provides baseline information on the octocoral assemblages, which can be useful for future ecological studies and marine biodiversity conservation efforts.

Understanding the resilience of temperate reefs to climate change requires exploring the recovery capacity of their habitat-forming species from recurrent marine heatwaves (MHWs). Here, we show that, in a Mediterranean highly enforced marine protected area established more than 40 years ago, habitat-forming octocoral populations that were first affected by a severe MHW in 2003 have not recovered after 15 years. Contrarily, they have followed collapse trajectories that have brought them to the brink of local ecological extinction. Since 2003, impacted populations of the red gorgonian Paramuricea clavata (Risso, 1826) and the red coral Corallium rubrum (Linnaeus, 1758) have followed different trends in terms of size structure, but a similar progressive reduction in density and biomass. Concurrently, recurrent MHWs were observed in the area during the 2003–2018 study period, which may have hindered populations recovery. The studied octocorals play a unique habitat-forming role in the coralligenous assemblages (i.e. reefs endemic to the Mediterranean Sea home to approximately 10% of its species). Therefore, our results underpin the great risk that recurrent MHWs pose for the long-term integrity and functioning of these emblematic temperate reefs. [ABSTRACT FROM AUTHOR]

The current knowledge on the diversity of the genus Plexaurella is based on a series of dated revisions, often with no examination of types. Although being common octocorals in western Atlantic reefs, there is no consensus on an exact number of valid species. Furthermore, phylogenetic reconstructions do not support the current classification of Plexaurella within the family Plexauridae. Thus, this study reviews the genus based on examination of available types and assesses monophyly using mitochondrial (COI+igr , mtMutS) and nuclear (28S) markers, mostly from available molecular data. Until now, up to six species were considered valid. Our results show that the group is composed of at least seven previously described species: P. dichotoma , P. nutans , P. grisea , P. teres , P. grandiflora , P. regia and P. obesa ; and one new species: Plexaurella rastrera sp. nov. An illustrated key to the valid species and a list of all available names are provided and the current classification of the genus is discussed. Based on congruent phylogenetic reconstructions and genetic distances, we propose the elevation of the former plexaurid subfamily Plexaurellinae to family level. Finally, based on examination of types, we propose the synonymy between Pseudoplexaura crucis and Plexaurella tenuis under Pseudoplexaura tenuis new comb. Corals of the genus Plexaurella are conspicuous sea fans from Caribbean and Brazilian reefs. Although known for more than a century, there was an uncertainty regarding on how many species comprised the group or in which family they should be placed. Herein, based on morphological and molecular evidence, we review the species of the genus and reconstruct the recent evolutionary history, concluding that eight species are valid, one of which is new. Our analyses also illustrate the need to establish a family for these corals, called Plexaurellidae. [ABSTRACT FROM AUTHOR]

Foundation species (FS) regulate ecological processes within communities often facilitating biodiversity and habitat complexity. Typically FS are dominant structure-forming taxa; but less dominant taxa having disproportionate ecological impacts to the community can also be FS. Mesophotic coral ecosystems (MCEs) are deep coral reef (∼30–150 m) communities, often dominated by emergent sponges in the Caribbean Basin. Despite the potential competitive advantage of sponges on MCEs, gorgonians are also common constituents of these reefs. Data from the Bahamas demonstrate increased biodiversity and densities of sponges on mesophotic reefs with gorgonians relative to reefs without these species. Drawing upon fifteen years of field surveys at five sites in the Caribbean Basin we assessed in situ interactions between gorgonians and sponges to quantify outcomes consistent with competition (i.e., tissue necrosis and overgrowth). Gorgonians were effective competitors against a variety of sponges, and two allelochemicals produced by Ellisella elongata were mechanistically important in interactions with Agelas clathrodes. We also examined invertebrate recruitment patterns near gorgonians to assess their role in facilitating MCE biodiversity. Our results indicate that live gorgonians, Antillogorgia bipinnata and E. elongata, facilitate biodiverse recruitment into MCEs, indicating that this process is governed by more than passive hydrodynamics. Collectively, these data indicate that these gorgonians exhibit both positive and negative ecological interactions (i.e., facilitation and competition, respectively) with sponges, and other taxa. Thus, these gorgonians are FS of MCE communities within the Caribbean Basin that display several traits contributing to the ecological structure of these understudied communities.

Studies concerning octocoral species from the Persian Gulf coral reefs are few. This study documents the diversity and abundance of octocoral communities from three islands in the north Persian Gulf, namely, Larak Island, Hengam Island and Qeshm Island. Belt transects were used to survey the octocoral communities at these islands. We used a rapid ecological assessment technique (REA) to assess the status and abundance of octocorals. Also, K Independent sample analysis was conducted on abundance and Shannon Diversity index data to determine if octocoral abundance and species diversity varied between islands. A total of 22 morphospecies, belonging to seven alcyonacean families, including Plexauridae, Ellisellidae, Alcyoniidae, Nephtheidae, Briareidae, Acanthogorgiidae and Subergorgiidae, were identified in this study. Statistical analysis indicated octocoral abundance and diversity at Larak Island reefs were higher than those around Hengam and Qeshm islands. The primary data presented in this study could serve as the baseline data for long-term biomonitoring programmes to estimate the status of octocorals in the Persian Gulf. [ABSTRACT FROM AUTHOR]

Since about the turn of the millennium, octocorals have been increasing in abundance on Caribbean reefs. The mechanisms underlying this trend have not been resolved, but the emergent species assemblage appears to be more resilient than the scleractinians they are replacing. The sea fan Gorgonia ventalina is an iconic species in the contemporary octocoral fauna, and here its population dynamics are described from St. John, US Virgin Islands, from 2013 to 2019. Mean densities of G. ventalina at Yawzi Point (9-m depth) varied from 1.4–1.5 colonies m−2, and their mean heights from 24–30 cm; nearby at Tektite (14-m depth), they varied from 0.6–0.8 colonies m−2 and from 25–33 cm. These reefs were impacted by two Category 5 hurricanes in 2017, but neither the density of G. ventalina, the density of their recruits (< 5-cm tall), nor the height of colonies, differed among years, although growth was depressed after the hurricanes. Nevertheless, at Tektite, colony height trended upwards over time, in part because colonies 10.1–20 cm tall were reduced in abundance after the hurricanes. These trends were sustained without density-associated effects mediating recruitment or self-thinning of adults. The dynamics of G. ventalina over seven years reveals the high resilience of this species that will contribute to the persistence of octocorals as a dominant state on Caribbean reefs.

Members of Scleraxonia Studer, 1887 are one of the most dominant megafaunal taxa on seamounts, but their diversity and spatial distribution are poorly known in the tropical Western Pacific. Among this group, the family Victorgorgiidae Moore et al., 2017 is typically characterized by josephinae clubs in their polyp tentacles and a remarkable purple color but remains one of the most poorly known scleraxonian taxa currently. Victorgorgiidae contains only the genus VictorgorgiaLópez-González and Briand, 2002 and six species. Here we describe three new species of Victorgorgia, V. fasciculata sp. nov., V. iocasica sp. nov., V. flabellata sp. nov., and re-describe V. eminensMoore et al., 2017, based on samples collected from four seamounts in the tropical Western Pacific, and evaluate their phylogenetic position using sequence data of mtMutS and COI genes. These new species are distinguished from each other and congeners by the sclerite forms and sizes, colony characters and polyp arrangement, and particularly the sclerites in the polyps and medulla are found to be most informative. Phylogenetic analyses indicate that V. flabellata sp. nov. is the sister group of V. iocasica sp. nov., and V. eminensMoore et al., 2017 showed a close relationship with Victorgorgia sp. GU563313. However, genetic divergence at the species level was found to be inadequate for differentiation of some close species. Each of the four species was found only from a single seamount, suggesting limited biological connectivity among the four seamount gorgoniians. Our study increases our understanding of the species diversity of Victorgorgiidae, and highlights the need for further research on the diversity and zoogeography of the deep-sea gorgonians.V. fasciculata sp. nov. urn:lsid:zoobank.org:act: 6CDEECC5-B96D-4DDF-95D2-32BEC3DBC938.V. iocasica sp. nov. urn:lsid:zoobank.org:act: BB11D217-C298-401F-8E13-849C33B03905.V. flabellata sp. nov. urn:lsid:zoobank.org:act: 2C0FCCF2-33B1-4C2D-AC8E-6737079422F4.urn:lsid:zoobank.org:pub: 39AF43F8-C0C2-4670-BBA0-DC1A7F1FA01B.

Three new sea fan species of Leptogorgia were discovered during multiple scuba diving expeditions along the Gulf of California coast and islands. Leptogorgia iridis sp. nov. is distributed in the southern region of the gulf (Mexican Province), inhabiting tropical rocky reefs of the Islas Marías Archipelago (Nayarit) and Bahía Banderas (Jalisco). This species has small colonies (< 7 cm height) with at least five clearly distinct chromotypes. Leptogorgia martirensis sp. nov. was found exclusively on the rocky reefs of San Pedro Mártir and San Esteban Islands located in the northern region of the Gulf of California (northern region of Cortez Province). Leptogorgia enrici sp. nov. is distributed from the south to the northern region of the Gulf of California (Cortez Province), inhabiting substrates of rocky reefs, sandy and pebbly sea floors. Comprehensive ecological diving expeditions to identify and classify octocorals in the Mexican Pacific (1995-2019) indicate that L. iridis sp. nov. and L. martirensis sp. nov. are likely to be micro-endemics and L. enrici sp. nov. is endemic to the Gulf of California, which defines their currently known biogeographic distribution ranges. [ABSTRACT FROM AUTHOR]

Coral reefs throughout the tropics have experienced large declines in the abundance of scleractinian corals over the last few decades, and some reefs are becoming functionally dominated by animal taxa other than scleractinians. This phenomenon is striking on many shallow reefs in the tropical western Atlantic, where arborescent octocorals now are numerically and functionally dominant. Octocorals are one of several taxa that have been overlooked for decades in analyses of coral reef community dynamics, and our understanding of why octocorals are favoured (whereas scleractinians are not) on some modern reefs, and how they will affect the function of future reef communities, is not commensurate with the task of scientifically responding to the coral reef crisis. We summarize the biological and ecological features predisposing octocorals for success under contemporary conditions, and focus on those features that could have generated resistance and resilience of octocoral populations to environmental change on modern reefs. There is a rich set of opportunities for rapid advancement in understanding the factors driving the success of octocorals on modern reefs, but we underscore three lines of inquiry: (1) the functional implications of strongly mixotrophic, polytrophic, and plastic nutrition, (2) the capacity to recruit at high densities and maintain rapid initial rates of vertical growth, and (3) the emergent properties associated with dense animal forests at high colony densities. [ABSTRACT FROM AUTHOR]

The species of the genus Psammogorgia Verrill, 1868 from the shallow waters of the tropical eastern Pacific were mainly described from 1846 to 1870. Very few contributions were published subsequently. Recently, the genus was revisited with the addition of two new species. However, a comprehensive generic study is still missing for the eastern Pacific. Psammogorgia is characterised by having axes cores without mineralisation, mainly coarse irregular spindles and thorny, leafy or tuberculate clubs coenenchymal sclerites and the anthocodial armature with distinct collaret and points arrangements. Herein a taxonomic revision of the genus is presented based on type material which was morphologically analysed and illustrated using optical and scanning electron microscopy. Comparative character tables are provided for comparison among species in the genus, along with a taxonomic key. Moreover, the taxonomic status of each species was analysed. The genus Psammogorgia comprises six valid species and two varieties, and three lectotypes and a new combination are proposed to establish the taxonomic status of these species. [ABSTRACT FROM AUTHOR]

Previous studies have demonstrated that gorgonians produce secondary metabolites that act as chemical defenses against predators and pathogens in the reef environment. While there have been investigations of the gorgonacea of the Western Atlantic which have shown that these organisms do contain defensive chemistry, the chemical ecology of Indo-Pacific gorgonians has not been investigated. The goal of this thesis research was to investigate the ecological role of Indo-Pacific gorgonian secondary metabolites in mediating interactions with potential predators and pathogens and to identify and describe the secondary metabolites responsible for observed activity.This dissertation concerns Indo-Pacific gorgonian chemical defenses against predation by the generalist reef fish Thalassoma lunare and Halichoeres melanurus, and against the growth of fungi isolated from gorgonian tissues, including the known gorgonian pathogen Aspergillus sydowii. The identification and characterization of novel secondary metabolites from gorgonians is also presented in this dissertation.The information gathered in these surveys led to projects involving gorgonian species of particular interest, with the aim of revealing the compound or compounds responsible for observed activities. Each project is described both biologically and chemically. The biological aspects described are the taxonomic identification of gorgonians and fungal strains. and the testing of extracts and pure compounds in assays. The chemical studies involve the isolation and structure elucidation of known and novel gorgonian secondary metabolites. The possible importance of specific compounds,or in some cases a class of compounds. in the chemical ecology of gorgonians is discussed.

There is little scientific information about the epizoic macroalgae that grow on octocorals, which is why they were identified in fore reefs near contaminated river basins off the coast of Havana, Cuba. A sampling was carried out in each station between September 2008 and January 2009 with a quadrat of 1 m side. The quadrats were positioned on the coral-rocky substrate at 10 m depth through a randomsystematic design. Five sites were selected: a site impacted by the discharges of the Bay of Havana (AM), three by the dumping of the Quibú River (ES, CH, IDO) and a site with little impact on the Bajo de Santa Ana (BSA). 59 species of epizoic macroalgae were found on 13 species of octocorals. The most abundant species of macroalgae were Amphiroa fragilissima, Jania adhaerens and Polysiphonia sp. The octocorals with the highest level of epizoism were Pterogorgia citrina, Eunicea flexuosa and Antillogorgia americana. The highest epizoic richness was detected in AM and the lowest in BSA. The analysis of the non-metric multidimensional scaling (nmMDS) showed spatial variations in the composition and abundance of epizoic, where BSA and AM are opposed, while the rest of sites are more similar to AM than to BSA, despite the geographic distances. The discharges from the Bay of Havana and the Quibú River seem to determine the differences in the richness and distribution of epizoic macroalgae on the Havana coastline. [ABSTRACT FROM AUTHOR]

A massive die-off of benthic suspension feeders (BSF) covered by large amounts of sediments was observed along Prince Islands coasts (north-eastern Sea of Marmara) in August 2015. Alcyonarians, pennatulaceans, bivalves and sponges were severely affected. Many BSF probably died from burial and clogging of their feeding and respiratory apparatus. Of the gorgonian colonies, 66 ± 34% (mean ± SD) were dead, while 15 ± 16% (mean ± SD) displayed recent necrosis on the colony surface. In addition, histopathological and microbial examinations of the affected gorgonians and gold corals (Savalia savaglia) suggest that stress caused by sedimentation made them vulnerable to exploitation by consistently isolated opportunistic microorganisms. We isolated Vibrio splendidus and Vibrio neptunius from diseased gold coral colonies, but the bacterial isolates obtained from gorgonians could only be identified to genus Vibrio level. The presumably artificially introduced fungus Mucor circinelloides was common on both gold coral and gorgonians. This mould and opportunistic bacteria may have colonized BSF by taking advantage of low oxygen levels leading to impaired coral immune responses and thereby exacerbated the BSF mortality. Construction and landfill operations at Yassıada seem to be the greatest contributor to the observed sedimentation, as shown by silicate concentrations in nearby waters. These observations imply that preventive measures are necessary when construction operations take place in the vicinity of sensitive marine habitats. [ABSTRACT FROM AUTHOR]

In this work, the consequences of a local gorgonian coral mortality on the whole coralligenous assemblage were studied. A Before/After-Control/Impact sampling design was used: the structure of the coralligenous assemblage was compared before and after the gorgonian mortality event at the mortality site and two control sites. At the mortality site, a relevant decrease in alpha and beta diversity occurred, with a shift from a stratified assemblage characterized by gorgonians and other invertebrates to an assemblage dominated by algal turfs; conversely, neither significant variations of the structure nor decrease in biodiversity were observed at the control sites. The assemblage shift involved the main taxa in different times: in autumn 2018, a large proportion of the plexaurid coral Paramuricea clavata died, but no significant changes were observed in the structure of the remaining assemblage. Then, in autumn 2019, algal turfs increased significantly and, one year later, the abundance of the gorgonian Eunicella cavolini and bryozoans collapsed. Although the mechanisms of the assemblage shift following gorgonian loss will remain uncertain and a cause-effect relationship cannot be derived, results suggest the need for detecting signs of gorgonian forests stress in monitoring programs, which should be considered early indicators of their condition. in the coralligenous monitoring programs for detecting any sign of gorgonian forests stress which should be considered an early indicator of the assemblage condition.

Zoantharians are a group of cnidarians that are often found in association with marine invertebrates, including corals, in shallow and deep-sea environments. However, little is known about deep-sea zoantharian taxonomy, specificity and nature of their associations with their coral hosts. In this study, analyses of molecular data (mtDNA COI, 16S, and 12S rDNA) coupled with ecological and morphological characteristics were used to examine zoantharian specimens associated with cold-water corals (CWC) at depths between 110 and 800 m from seamounts and island slopes in the Azores region. The zoantharians examined were found living in association with stylasterids, antipatharians and octocorals. From the collected specimens, four new species were identified: (1) Epizoanthus martinsae sp. n. associated with the antipatharian Leiopathes sp.; (2) Parazoanthus aliceae sp. n. associated with the stylasterid Errina dabneyi (Pourtalès, 1871); (3) Zibrowius alberti sp. n. associated with octocorals of the family Primnoidae [Paracalyptrophora josephinae (Lindström, 1877)] and the family Plexauridae (Dentomuricea aff. meteor Grasshoff, 1977); (4) Hurlizoanthus hirondelleae sp. n. associated with the primnoid octocoral Candidella imbricata (Johnson, 1862). In addition, based on newly collected material, morphological and molecular data and phylogenic reconstruction, the zoantharian Isozoanthus primnoidus Carreiro-Silva, Braga-Henriques, Sampaio, de Matos, Porteiro & Ocaña, 2011, associated with the primnoid octocoral Callogorgia verticillata (Pallas, 1766), was reclassified as Zibrowius primnoidus comb. nov. The zoantharians, Z. primnoidus comb. nov., Z. alberti sp. n., and H. hirondelleae sp. n. associated with octocorals showed evidence of a parasitic relationship, where the zoantharian progressively eliminates gorgonian tissue and uses the gorgonian axis for structure and support, and coral sclerites for protection. In contrast, the zoantharian P. aliceae sp. n. associated with the stylasterid E. dabneyi and the zoantharian E. martinsae sp. n. associated with the antipatharian Leiopathes sp., appear to use the coral host only as support with no visible damage to the host. The monophyly of octocoral-associated zoantharians suggests that substrate specificity is tightly linked to the evolution of zoantharians.Zibrowius alberti sp. n. urn:lsid:zoobank.org:act:8E186AD4-CA6E-419B-B46A-4C8D11C757DDHurlizoanthus hirondelleae sp. n. urn:lsid:zoobank.org:act:6737B10E-9E87-4BA0-9559-C22D49863732Parazoanthus aliceae sp.n. urn:lsid:zoobank.org:act:3D3AA61D-E5CC-47DF-94F1-A4A2FF59ABEAEpizoanthus martinsae sp. n. urn:lsid: zoobank.org:act:04686BB5-03D7-4132-B52B-CC89DF8EBFA8urn:lsid:zoobank.org:pub:FED88229-30F9-481F-9155-FF481790AE5C

In this study, the demography of the common demospongeIrcinia felixwas examined at Tamarindo, a coral reef located in the island municipality of Culebra, Puerto Rico. A preliminary study comparing the size structure of two subpopulations within the reef, Tamarindo Norte (TN) and Tamarindo Sur (TS), indicated that sponges at TN are significantly larger than sponges at TS. This result served as a baseline for the present comparative study in which we aimed to determine whether the spatial differences in population size structure can be explained either by a difference in rates of survival, growth, or recruitment, or a combination of these. To accomplish our goal, we followed the growth, survival and recruitment ofI. felixat the two localities for one year. Growth was the only demographic parameter that differed significantly between localities. Because the most obvious distinction between the study sites was the absence of the octocoralGorgonia ventalinaat TS, we hypothesized that the faster overall growth rate of sponges at TN was related to the presence of the octocoral. To test this hypothesis, we compared growth rates between sponges associated with the octocoral and those individuals not associated. We found that sponges growing nearG. ventalinagrew significantly faster than non-associated sponges. This result suggests that the octocoral facilitates the growth ofI. felixand therefore may account, at least in part, for the spatial differences in population size structure. [ABSTRACT FROM AUTHOR]

The clingfish Lecanogaster gorgoniphila new species, an unusual species associated with gorgonians, is described on the basis of 7 specimens and colour photographs from São Tomé Island, São Tomé and Principe, eastern Atlantic Ocean. The species is small, probably not exceeding 28 mm total length; it is characterized by having 4-5 dorsal-fin rays, 3-4 anal-fin rays, 21-23 pectoral-fin rays, and 11-14 principal caudal-fin rays; 12-14 rakers on third gill arch, very small, partially fused; papillae in centre of pelvic disk forming a round patch; pelvic disc region B with 5-6 rows of papillae; head relatively short, its length 2.4- 3.4 in SL, and relatively narrow, its width 4.5-7.4 in SL; colouration of head and body variable in life, usually dorsally reddish white, ventrally rose, with eight bright red bars with scattered white spots. The new species is compared with other species of the eastern Atlantic genera Lecanogaster and Diplecogaster; a key to the species of the genus Lecanogaster Briggs, 1957 is presented. [ABSTRACT FROM AUTHOR]

Molecular analyses of the ecologically important gorgonian octocoral genus Leptogorgia are scant and mostly deal with few species from restricted geographical regions. Here we explore the phylogenetic relationships and the evolutionary history of Leptogorgia using the complete mitochondrial genomes of six Leptogorgia species from different localities in the Atlantic, Mediterranean and eastern Pacific as well as four other genera of Gorgoniidae and Plexauridae. Our mitogenomic analyses showed high inter-specific diversity, variable nucleotide substitution rates and, for some species, novel genomic features such as ORFs of unknown function. The phylogenetic analyses using complete mitogenomes and an extended mtMutS dataset recovered Leptogorgia as polyphyletic, and the species considered in the analyses were split into two defined groups corresponding to different geographic regions, namely the eastern Pacific and the Atlantic-Mediterranean. Our phylogenetic analysis based on mtMutS also showed a clear separation between the eastern Atlantic and South African Leptogorgia , suggesting the need of a taxonomic revision for these forms. A time-calibrated phylogeny showed that the separation of eastern Pacific and western Atlantic species started ca. 20 Mya and suggested a recent divergence for eastern Pacific species and for L. sarmentosa-L. capverdensis . Our results also revealed high inter-specific diversity among eastern Atlantic and South African species, highlighting a potential role of the geographical diversification processes and geological events occurring during the last 30 Ma in the Atlantic on the evolutionary history of these organisms. [ABSTRACT FROM AUTHOR]

Octocorals (Cnidaria, Anthozoa Octocorallia) are magnificent repositories of natural products with fascinating and unusual chemical structures and bioactivities of interest to medicine and biotechnology. However, mechanistic understanding of the contribution of microbial symbionts to the chemical diversity of octocorals is yet to be achieved. This review inventories the natural products so-far described for octocoral-derived bacteria and fungi, uncovering a true chemical arsenal of terpenes, steroids, alkaloids, and polyketides with antibacterial, antifungal, antiviral, antifouling, anticancer, anti-inflammatory, and antimalarial activities of enormous potential for blue growth. Genome mining of 15 bacterial associates (spanning 12 genera) cultivated from Eunicella spp. resulted in the identification of 440 putative and classifiable secondary metabolite biosynthetic gene clusters (BGCs), encompassing varied terpene-, polyketide-, bacteriocin-, and nonribosomal peptide-synthase BGCs. This points towards a widespread yet uncharted capacity of octocoral-associated bacteria to synthetize a broad range of natural products. However, to extend our knowledge and foster the near-future laboratory production of bioactive compounds from (cultivatable and currently uncultivatable) octocoral symbionts, optimal blending between targeted metagenomics, DNA recombinant technologies, improved symbiont cultivation, functional genomics, and analytical chemistry are required. Such a multidisciplinary undertaking is key to achieving a sustainable response to the urgent industrial demand for novel drugs and enzyme varieties.

The Nazaré submarine canyon extends ~ 210 km westward from the coast of Portugal, down to a water depth of > 4300 m. The considerable habitat heterogeneity found throughout the canyon is affected by strong currents and high turbidity, especially in the upper parts of the canyon. The canyon morphology comprises steep slopes, scarps, terraces, and overhangs, and a deeply incised thalweg is found in the lower part of the canyon. The seabed within the canyon is composed of varying proportions of rock and sediments that range from sand to fine mud. This great variation in physical environment is reflected by the varied fauna inhabiting the canyon. Diversity tends to decrease with depth, but there is also continual replacement of species with increasing water depth. Certain groups, such as the gorgonians and sea lilies, tend to be found on rocky surfaces, while large protozoans dominate the sediments at 3400-m depth. In addition to describing the fauna of Nazaré Canyon, we discuss experiments undertaken as part of the HERMES project to elucidate the ecosystem function processes operating in the deeper parts of the canyon.