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Zoantharians (Cnidaria: Hexacorallia: Zoantharia) of the genus Palythoa are ubiquitous species that occupy reef habitats in every tropical ocean. Disagreements among classifications based on morphology, reproductive traits, and molecular techniques have generated taxonomic challenges within this group. Molecular studies provide limited phylogenetic resolution between species, and discordance is frequently attributed to slow mitochondrial rates and lack of resolution among molecular markers. Here we conducted the first phylogenomic survey of Palythoa, using a reduced representation genomic approach (ezRAD) to resolve relationships among eight described and four putative Palythoa species (N = 22 plus two outgroups) across the Pacific and Atlantic Oceans. We constructed nearly complete mitochondrial genomes and assembled transcriptome loci datasets by reference mapping. A de novo assembly was performed for the holobiont dataset, and we compared a range of filtering strategies from unfiltered data down to 136 unlinked high-quality biallelic SNPs shared by all samples to resolve evolutionary lineages within Palythoa. Across all these datasets, the resulting Bayesian and ML trees revealed six highly concordant and well-supported clades, however, the phylogenomic data were inconclusive in resolving species relationships within the clades. We detected putative species complexes within two well sampled Palythoa clades (clades I and II), but species delimitation results were inconsistent in whether these clades contain multiple nominal species or represent a single variable species. Polyphyly in the broadly distributed species Palythoa tuberculosa and P. mutuki highlight the need for additional study. Consistency among nuclear and mitogenomic datasets points to a lack of biological understanding of species boundaries among these zoantharians rather than limitations of the molecular markers. More complete taxonomic sampling of nominal species across the geographic ranges of distribution is necessary to resolve species boundaries and evolutionary histories among members of this genus.

Benthic cnidarians are suspension feeders that ingest items ranging from particulate organic matter to macrozooplankton. Additionally, many species receive photosynthetic products from associated endosymbiotic microalgae (Symbiodiniaceae). Although benthic cnidarians are ubiquitous to reef ecosystems, variation in their nutrition acquisition strategy across distinct environments is poorly understood. In this study, we evaluated the trophic niche and symbiotic interactions of the widespread species Palythoa tuberculosa (Hexacorallia: Zoantharia) inhabiting depths ranging from the intertidal to 35 m across three Indo-Pacific regions, using carbon and nitrogen stable isotope ratios and isotopic niche metrics. Our results revealed that populations in shallow (0-8 m) and deep zones (down to 35 m) had distinct niche placements and overlap with the endosymbionts’ niches across all regions. Associated Symbiodiniaceae were identified as Cladocopium. Contradicting the paradigm of a more productive endosymbiosis in shallower waters, P. tuberculosa had less isotopic niche overlap with its endosymbionts in shallow reefs (0–9%) but a higher niche overlap in deep waters (up to 70%). Among regions, this was most evident in Dongsha Atoll, South China Sea, which has comparatively high influence of internal waves and, thus, high concentrations of plankton. The low niche overlap with endosymbionts in shallow waters indicated that P. tuberculosa may have a high heterotrophic performance, which partially explains the species’ resilience during bleaching events. Regarding the distinct niche placements across depths, lower δ13C in the shallower zone could be due to light-driven effects on fixation by the endosymbionts. Additional non-exclusive explanations include that water flow regimes and nocturnal feeding behavior could enable P. tuberculosa populations to ingest more/distinct prey items, with lower δ13C, in the shallow compared to the deep zone. The nutritional plasticity of P. tuberculosa likely contributes to its widespread distribution and provides an advantage under a warming climate that will affect cnidarian-endosymbiont relationships.

In the Southwestern Atlantic reefs (SWA), some species of massive scleractinians and zoantharians are adapted to turbid waters, periodic desiccation, and sediment resuspension events. Moreover, phase shifts in this region have mostly been characterized by the emergence of algae and, less typically, zoantharians. However, nutrient excess and organic pollution are key drivers of the hard coral habitat degradation and may, thus, favor the emergence of novel zoantharian-dominated habitats. Many zoantharian species, particularly those from the genera Palythoa and Zoanthus, have traits that could help them thrive under conditions detrimental to reef-building corals, including rapid growth, several asexual reproduction strategies, high morphological plasticity, and generalist nutrient acquisition strategies. Thus, in a near future, stress-tolerant zoantharians may thrive in nutrient-enriched subtidal SWA locations under low heat stress, such as, upwelling. Overall, coral-zoantharian phase shifts in the SWA may decrease the species richness of fish and benthic communities, ultimately influencing ecosystem functioning and services, such as the provision of nursery habitats, fish biomass production, and coastline protection. However, zoantharians will also be threatened at intertidal zones, which are expected to experience higher heat stress, solar radiation, and sea-level rise. Although zoantharians appear to cope well with some local stressors (e.g., decreasing water quality), they are vulnerable to climate change (e.g., heatwaves), invasive species (Tubastraea spp.), microplastics, diseases, and mostly restricted to a narrow depth range (0–15 m depth) in SWA reefs. This shallow zone is particularly affected by climate change, compressing the three-dimensional habitat and limiting depth refugia in deeper SWA reefs. As mesophotic ecosystems have been hypothesized as short-term refuges to disturbances for some species, the narrow depth limit of zoantharians seems to be a potential factor that might increase their vulnerability to growing climate change pressures in SWA shallow-water reefs. Together, these could lead to both range expansions in some locations and loss of suitable reef habitats in other sites. Additional research is needed to better understand the systemic responses of these novel SWA reefs to the concert of increasing and interactive local and global stressors, and their implications for ecosystem functioning and service provisions.

Hexactinellid sponges are important members of deep-sea benthic ecosystems because they provide available hard substrate habitats for filter-feeding invertebrates. However, symbioses between hexactinellid sponges and their symbionts are poorly known. Zoantharians associated with hexactinellid sponges have been reported widely from deep-sea marine ecosystems, either on the bodies or stalks of hexactinellid sponges. Despite these records, there has been a lack of research on their diversity and phylogenetic relationships. In this study, 20 specimens associated with amphidiscophoran and hexasterophoran sponges were collected from the waters of Australia and Japan in the Pacific, and from Curaçao in the southern Caribbean, and these were examined in addition to museum specimens. Based on molecular phylogenetic analyses and morphological observations, we formally describe two new genera and three new species of Zoantharia and report several previously described species. The results suggest at least two independent origins for the symbioses between hexactinellid sponges and zoantharians. Our results demonstrate that the diversity of hexactinellid sponge-associated zoantharians is much higher than has been previously thought. The new taxa described in this work further reconfirm that the deep-sea harbours high levels of undescribed zoantharian diversity.

Symbioses between invertebrates are common in the ocean although usually the diversity and specificity of their interactions are not well understood. Parazoanthidae (Cnidaria: Anthozoa: Zoantharia) is one of the most diverse zoantharian families in terms of numbers of genera and species. Species in this family are commonly associated with various other invertebrates that they utilize as their substrate. Previous studies have re-organized the taxonomy of Parazoanthidae and revealed a strong specificity between many parazoanthid species and genera and their substrates. However, our understanding of the species diversity of Parazoanthidae is far from complete, as parazoanthids are often overlooked in sampling surveys. In this study, we establish three subgenera under the genus Umimayanthus Montenegro, Sinniger, and Reimer, 2015; the nominotypical Umimayanthus, Paraumimayanthus subgen nov., and Gorgoniazoanthus subgen. nov., based on the finding of a new species, Umimayanthus (Gorgoniazoanthus) kanabou sp. nov., associated with the sea-whip gorgonian Ellisella sp. from approximately 30 m depth in shallow mesophotic coral reef communities in Oura Bay on Okinawajima Island and in Oshima Strait near Amami-Oshima Island, in the Ryukyu Islands, southern Japan. We additionally report on gastropods and crustaceans observed in association with U. kanabou, and these species are thought to potentially prey upon the zoantharians or on gorgonian polyps. Umimayanthus kanabou is phylogenetically closely related to congeneric sponge-associated Umimayanthus spp., further supporting the recent hypothesis that substrate preferences may change during the evolutionary history of zoantharians.

The recently erected macrocnemic family Hydrozoanthidae comprises relatively few species recorded from tropical and subtropical regions. In the Atlantic Ocean, this family has been reported only fr...

In this study, a zoantharian specimen was found associated with a gorgonian colony of the genus Nicella (Anthozoa, Octocorallia), representing the first zoantharian-octocoral association reported from the southwestern Atlantic. Unexpectedly, phylogenetic analyses of mitochondrial (COI and mt 16S rDNA) and nuclear (ITS-rDNA) markers assigned the specimen to the widely distributed species Parazoanthus cf. swiftii, known until now to associate exclusively with sponges (Porifera). In the sampled locality (Alcatrazes Archipelago, Sao Paulo State), P. cf. swiftii has been observed to associate with both sponges and octocoral. We review the literature and discuss the specificity of biotic substrate associations in Zoantharia and suggest that many interactions may not be as host-specific as previously thought. Such flexibility in habitat choice may provide the mechanisms that have allowed zoantharians to adapt and associate with a wide range of invertebrate hosts across evolutionary time scales.

The Red Sea was one of the first areas of the Indo-Pacific to be investigated by marine taxonomists, and the literature on suborder Brachycnemina (Anthozoa: Hexacorallia: Zoantharia) for this region dates from the early nineteenth century. However, in the last 100 years there has been only one focused study on this group in the Red Sea. In the present study, specimens collected from the Saudi Arabian coast of the northern half of the Red Sea were phylogenetically analyzed by sequencing nuclear internal transcribed spacer regions of ribosomal DNA (ITS-rDNA), mitochondrial cytochrome oxidase subunit I (COI), and 16S ribosomal DNA (16S–rDNA). The new results were compared with historical data in the literature and recent results from the Persian Gulf and the southeastern coast of Africa. Results show the presence of six to seven potential Brachycnemina species in the Red Sea; five to six Palythoa species (Palythoa mutuki, P. tuberculosa, P. cf. heliodiscus, P. aff. heliodiscus, and one to two species within the P. sp. “sakurajimensis” group) together with Zoanthus sansibaricus. While P. mutuki, P. tuberculosa, and Z. sansibaricus are known to be widely distributed in the Indo-Pacific, P. cf. heliodiscus and P. sp. “sakurajimensis” have not been reported from the Persian Gulf or the southeastern coast of Africa, and the current results represent large range extensions for these two species. Only one of the observed species, P. aff. heliodiscus, is potentially endemic to the Red Sea, further demonstrating the generally wide distributions of most zooxanthellate Brachycnemina species.

Dongsha Atoll is the largest coral atoll in the South China Sea (SCS), and is expected to harbor high levels of biodiversity as the SCS is located adjacent to the recognized center of maximum marine biodiversity in the central Indo-Pacific (CIP). However, due to its relative isolation, the biodiversity of Dongsha Atoll has not yet been well investigated for most marine taxa. In this study, we report on findings from our survey in 2016 that focused on the order Zoantharia, for which only sporadic previous reports exist from the SCS. Our results indicate some species such as Palythoa tuberculosa are very common around Dongsha Atoll, as well as the presence of at least three undescribed species, including one species only found thus far at the atoll. Overall, we recorded 16 species of Zoantharia from Dongsha Atoll, bringing the total number of zoantharian species in the SCS to 22, close to numbers reported from the CIP (=24 spp.) and southern Japan (=28 spp.). These findings demonstrate the importance of protecting the biodiversity of Dongsha Atoll, and also, given the limited survey coverage, the potential for undiscovered biodiversity in the SCS.

Zoantharians (Cnidaria: Hexacorallia: Zoantharia) are sessile animals found from the intertidal zone to the abyssal ocean in a variety of marine ecosystems such as coral reefs and sandy seafloors. Although some Zoantharia species produce toxic secondary metabolites, their colonies serve as food sources and shelter to many organisms. The metabolites produced by zoantharians have shown promising results in the pharmacognosy industry. Additionally, some species are popular in the aquarium hobby or as jewelry. The order Zoantharia, with 9 families and 28 genera, has representatives occurring worldwide. Zoantharia are thought to have unique distribution patterns for marine anthozoans. For example, the group appears to have relatively low rates of endemism, with some species having very wide distributions inside each ocean basin. As well, there are several pairs of sibling species between the Atlantic and Indo-Pacific oceans. Due to the importance of the order Zoantharia, additional research in the systematics and distribution of species will help achieve a better understanding of evolution in marine ecosystems. In this article we provide an overview of the group and comment on possible future research trends.

Microplastics (MPs) are an environmental problem of growing concern, and several studies have defined the Bay of Biscay (BoB) as a marine litter accumulation area. To address the abundance of MPs in this region, a critical overview is presented compiling the research performed to date on the different water bodies, sediments and biota. The comparative assessment highlights high spatial and temporal variability in MP distribution. MPs appear in at least 50% of the samples in waters and sediments. Polypropylene, polyethylene, polyester and polystyrene are the most frequent polymers, with a significant predominance of fragments and fibres. The BoB can be considered a region with medium concentration of MPs. However, monitoring programmes are needed to compile data over time and thus evaluate the historical trends of MP pollution. The difficulty of comparing studies is highlighted, due to the use of different methodologies. Hence, the harmonisation of monitoring methods is urgently required.

Diversity surveys in isolated sites, such as oceanic islands, provide biogeographic data that can improve our analyses and knowledge of evolutionary processes in the oceans. Zoantharians (Cnidaria: Anthozoa) are common and widespread components of shallow-water reefs, but distributional analyses are scarce for this group. In this study, we collected Zoantharia specimens from around Saint Helena Island (STH) in the mid-Atlantic and identified species using external morphology and molecular data. Moreover, we compiled and analysed the most comprehensive distributional data for zoantharian species in the subtropical and tropical Atlantic Ocean to date. Our results show eight zoantharian species in STH, which includes seven new records for STH waters. Furthermore, all families and genera of the suborder Brachycnemina recorded are widespread in the Atlantic Ocean, including at least four amphi-Atlantic species. The Caribbean is the richness centre in the Atlantic Ocean for zoantharian species, a pattern similar to that observed for many other subtropical/tropical marine taxa. However, Zoantharia may have a lower endemism rate in some areas than other common reef animals, for example zooxanthellate scleractinian corals and reef fishes. Moreover, zoantharian species have a more extensive distribution than close-related taxa such as zooxanthellate scleractinian corals and hydrocorals in the Atlantic Ocean. Japanese Government (MEXT)Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT) JSPSMinistry of Education, Culture, Sports, Science and Technology, Japan (MEXT)Japan Society for the Promotion of Science

Marine recreational fisheries and fish communities have been mostly studied separately, severely hampering the detection of possible interactions. Here we monitored recreational fishery landings (angling and spearfishing) and assessed the reef fish community through underwater visual censuses in Trindade, an isolated oceanic island in the southwestern Atlantic Ocean. The study was conducted in zones of high and low fishing effort, along three different years spread over a seven-year period. We found high catch per unit effort (CPUE; kg*fisher−1*hour−1) associated with high fishing intensity. However, the biomass of the targeted species in the natural environment decreased by 58% over time, while fishing effort increased about 270%, and CPUE decreased by 40%. Inverse relationships between effort and CPUE, and effort and biomass in the environment, were stronger in zones of high fishing effort. We conclude that the recreational fishery activity quickly responded to overfishing, creating a harvesting process that negatively impacted reef fish communities in this isolated oceanic island. Thus, conservation strategies should incorporate long-term recreational catch and fish community monitoring programs. Here we discuss options for the sustainability of the recreational fisheries and reinforce the importance of dialogue among scientists, managers and users for the achievement of conservation goals.

Marine biodiversity and derived ecosystem services are critical to the healthy functioning of marine ecosystems, and to human economic and societal well-being. Thus, an understanding of marine biodiversity in different ecosystems is necessary for their conservation and management. Coral reefs in particular are noted for their high levels of biodiversity, and among the world’s coral reefs, the subtropical Ryukyu Islands (RYS; also known as the Nansei Islands) in Japan have been shown to harbor very high levels of marine biodiversity. This study provides an overview of the state of marine biodiversity research in the RYS. First, we examined the amount of English language scientific literature in the Web of Science (WoS; 1995–2017) on six selected representative taxa spanning protists to vertebrates across six geographic sub-regions in the RYS. Our results show clear taxonomic and sub-region bias, with research on Pisces, Cnidaria, and Crustacea to be much more common than on Dinoflagellata, Echinodermata, and Mollusca. Such research was more commonly conducted in sub-regions with larger human populations (Okinawa, Yaeyama). Additional analyses with the Ocean Biogeographic Information System (OBIS) records show that within sub-regions, records are concentrated in areas directly around marine research stations and institutes (if present), further showing geographical bias within sub-regions. While not surprising, the results indicate a need to address ‘understudied’ taxa in ‘understudied sub-regions’ (Tokara, Miyako, Yakutane, Amami Oshima), particularly sub-regions away from marine research stations. Second, we compared the numbers of English language scientific papers on eight ecological topics for the RYS with numbers from selected major coral reef regions of the world; the Caribbean (CAR), Great Barrier Reef (GBR), and the Red Sea (RES). As expected, the numbers for all topics in the RYS were well below numbers from all other regions, yet within this disparity, research in the RYS on ‘marine protected areas’ and ‘herbivory’ was an order of magnitude lower than numbers in other regions. Additionally, while manuscript numbers on the RYS have increased from 1995 to 2016, the rate of increase (4.0 times) was seen to be lower than those in the CAR, RES, and GBR (4.6–8.4 times). Coral reefs in the RYS feature high levels of both endemism and anthropogenic threats, and subsequently they contain a concentration of some of the world’s most critically endangered marine species. To protect these threatened species and coral reef ecosystems, more data are needed to fill the research gaps identified in this study.

The increasing availability of human-made structure in the oceans coupled with climate changes may lead to the range expansion of species able to disperse by rafting. In this study, we report on zoantharian species of genera Isaurus, Palythoa, Umimayanthus and Zoanthus covering artificial substrates in locations in both the Atlantic and Pacific oceans. Moreover, we reviewed observations of additional zoantharians as macrofouling organisms, and discuss the possible role of rafting in the dispersal of this cosmopolitan group. Traits reported to some zoantharian species, such as hermaphroditism and resistance to desiccation, support their dispersal potential by drifting attached to floating objects. Further reports of zoantharian species covering floating artificial structures and natural debris are needed to increase our knowledge of dispersal mechanisms in the oceans. Additionally, this information is essential to monitor and manage possible exotic species invasions, especially for zoantharian species that are common in the aquarium trade.

The recently described aragonite skeleton-forming octocoral species Nanipora kamurai (Cnidaria: Anthozoa: Octocorallia: Helioporacea) is known from only one locality in Okinawa, Japan. This locality, Ama Beach on Zamami Island, is a shallow (1 to 1.5 m deep) sandy reef moat popular with recreational swimmers and snorkelers during summer months. Additionally, the species has been reported to be rare at this site, although no concrete survey data existed. This study quantitatively investigated the rarity of N. kamurai at this site via examining all rocks and rubble within a transect survey (n = 6) of 2400 m2. Our results show that N. kamurai is indeed low in number, with only eight colonies found over the entire survey area. Of coral rubble and rocks examined, only slightly more than 1 % of rocks had N. kamurai colonies (8/739 rocks), for a density of 0.003 colonies per m2. As this species is low in abundance and known from only Ama Beach, local management to ensure the designated recreational swimming area at this location should be undertaken.

Zoantharia (Hexacorallia) is an order of benthic cnidarians, which are known to play an important ecological role in many marine ecosystems. Although the order has a cosmopolitan distribution, including the tropical southwestern Atlantic, research on Brazilian zoantharian species diversity and distribution patterns is lacking. In order to start addressing this gap, we conducted shallow-water coastal and oceanic island sampling in parallel with an extensive literature review to summarize the knowledge of the order Zoantharia from Brazil. Additionally, mitochondrial 16S ribosomal DNA and cytochrome oxidase subunit I (COI) sequences from specimens were determined to confirm their identity and phylogenetic position within the order. Our results show the presence of at least 13 zoantharian species in Brazilian waters, including first records of Palythoa aff. clavata and Zoanthus aff. pulchellus. Moreover, range extensions were confirmed for Palythoa caribaeorum, P. grandiflora, P. variabilis, Zoanthus pulchellus, and Parazoanthus swiftii. We also present the first report on the distribution patterns for all studied species in Brazil. The current study is expected to provide a baseline for further surveys in the tropical southwestern Atlantic, where Zoantharia species richness is still understudied and therefore very likely underestimated.

Based on literature review, recent surveys, and specimens’ identification, we examined benthic cnidarian species richness across the oceanic Trindade and Martin Vaz Archipelago (TMA), Southwestern Atlantic Ocean. A total of 37 species (three Hydrozoa and 34 Anthozoa) are reported, including seven new records. The zooxanthellate scleractinian corals Montastraea cavernosa, Mussismilia hispida, Mussismilia leptophylla and Siderastrea stellata were the most commonly found species, while some species, such as the azooxanthellate coral Polycyahtus sp., were only found at one site. Although Martin Vaz Island has a lower diversity (11 species) compared to Trindade Island (37 species), fewer studies have been conducted in the former. Likewise, research in the TMA has focused on shallow water communities (