Anemonefish are better taxonomists than humans

The symbiosis between giant sea anemones, algae of the family Symbiodiniaceae, and anemonefish is an iconic example of a mutualistic trio1,2. Molecular analyses have shown that giant sea anemones hosting anemonefish belong to three clades: Entacmaea, Stichodactyla, and Heteractis3,4,5 (Figure 1A). Associations among 28 species of anemonefish and 10 species of giant sea anemone hosts are complex. Some fish species are highly specialized to only one anemone species (e.g., Amphiprion frenatus with Entacmaea quadricolor), whereas others are more generalist (e.g., Amphiprion clarkii)1,2,6. Reasons for host preferences are obscured, among other things, by the lack of resolution in the giant sea anemone phylogeny. Here, we generated a transcriptomic dataset from 55 sea anemones collected from southern Japan to reconstruct these phylogenetic relationships. We observed that the bubble-tip sea anemone E. quadricolor, currently considered a single species, can be separated into at least four cryptic lineages (A-D). Surprisingly, these lineages can be precisely distinguished by observing their association with anemonefish: A. frenatus only associates with lineage D, whereas A. clarkii lives in the other three lineages.

Abundance and distribution of marine litter on the beaches of Okinawa Island, Japan

This study evaluated the distribution and abundance of marine litter on 30 beaches around Okinawa Island, Japan. Beach quality indices and multivariate statistical analyses were used to assess the quality of the beaches and their pollution patterns. A total of 11,626 items weighing 513.49 kg with an average density of 0.13 ± 0.10 items/m2 were collected. Litter was dominated by plastics (81.72 %), broken glass (8.38 %), and cigarette butts (7.44 %), and 74.05 % of total litter was from land-based sources. Single-use plastics (SUPs) were present in all surveyed beaches and made up 30.54 % of the total litter. The clean coast index (CCI), plastic abundance index (PAI), and hazardous index (HI) were between 0.1 and 7.6, 0.1-4.0 and 0.01-1.42, respectively, indicating low to moderate levels of pollution of Okinawan beaches. This study should aid in the formation of strategies to deal with marine litter in Okinawa, other areas of Japan and the Asia-Pacific region.

Genome sizes and repeatome evolution in zoantharians (Cnidaria: Hexacorallia: Zoantharia)

Across eukaryotes, large variations of genome sizes have been observed even between closely related species. Transposable elements as part of the repeated DNA have been proposed and confirmed as one of the most important contributors to genome size variation. However, the evolutionary implications of genome size variation and transposable element dynamics are not well understood. Together with phenotypic traits, they are commonly referred to as the "C-value enigma". The order Zoantharia are benthic cnidarians found from intertidal zones to the deep sea, and some species are particularly abundant in coral reefs. Despite their high ecological relevance, zoantharians have yet to be largely studied from the genomic point of view. This study aims at investigating the role of the repeatome (total content of repeated elements) in genome size variations across the order Zoantharia. To this end, whole-genomes of 32 zoantharian species representing five families were sequenced. Genome sizes were estimated and the abundances of different repeat classes were assessed. In addition, the repeat overlap between species was assessed by a sequence clustering method. The genome sizes in the dataset varied up to 2.4 fold magnitude. Significant correlations between genome size, repeated DNA content and transposable elements, respectively (Pearson's correlation test R2 = 0.47, p = 0.0016; R2 = 0.22, p = 0.05) were found, suggesting their involvement in the dynamics of genome expansion and reduction. In all species, long interspersed nuclear elements and DNA transposons were the most abundant identified elements. These transposable elements also appeared to have had a recent expansion event. This was in contrast to the comparative clustering analysis which revealed species-specific patterns of satellite elements' amplification. In summary, the genome sizes of zoantharians likely result from the complex dynamics of repeated elements. Finally, the majority of repeated elements (up to 70%) could not be annotated to a known repeat class, highlighting the need to further investigate non-model cnidarian genomes. More research is needed to understand how repeated DNA dynamics relate to zoantharian evolution and their biology.

Macroalgae exhibit diverse responses to human disturbances on coral reefs

Scientists and managers rely on indicator taxa such as coral and macroalgal cover to evaluate the effects of human disturbance on coral reefs, often assuming a universally positive relationship between local human disturbance and macroalgae. Despite evidence that macroalgae respond to local stressors in diverse ways, there have been few efforts to evaluate relationships between specific macroalgae taxa and local human-driven disturbance. Using genus-level monitoring data from 1205 sites in the Indian and Pacific Oceans, we assess whether macroalgae percent cover correlates with local human disturbance while accounting for factors that could obscure or confound relationships. Assessing macroalgae at genus level revealed that no genera were positively correlated with all human disturbance metrics. Instead, we found relationships between the division or genera of algae and specific human disturbances that were not detectable when pooling taxa into a single functional category, which is common to many analyses. The convention to use percent cover of macroalgae as an indication of local human disturbance therefore likely obscures signatures of local anthropogenic threats to reefs. Our limited understanding of relationships between human disturbance, macroalgae taxa, and their responses to human disturbances impedes the ability to diagnose and respond appropriately to these threats.

Review of microplastics in museum specimens: An under-utilized tool to better understand the Plasticene

This study summarises the status of microplastic research in marine and freshwater specimens in natural museum collections around the world. Abundances, distributions, and types of microplastics in the archived collections are discussed. Museum collections can fill knowledge gaps on evolution of microplastic pollution before and during the Plasticene era. The specimens in these studies, ranging from plankton to vertebrates, were collected and archived between 1900 and 2019, and are dominated by specimens from marine ecosystems. All the specimens included in this review were preserved by freezing or in ethanol/formaldehyde except for specimens in one study that were preserved via cryomilling. Microfibers were the most common microplastics in the reviewed studies. We recommend more microplastic studies over a wider taxonomic range of species and across a longer span of years utilizing archival specimen collections around the world in order to establish reference points and develop temporal trends for microplastic pollution of the environment.

Evolutionary patterns of host switching, lifestyle mode, and the diversification history in symbiotic zoantharians

Symbioses play important roles in forming the structural and distributional patterns of marine diversity. Understanding how interspecies interactions through symbioses contribute to biodiversity is an essential topic. Host switching has been considered as one of the main drivers of diversification in symbiotic systems. However, its process and patterns remain poorly investigated in the marine realm. Hexacoral species of the order Zoantharia (=zoantharians) are often epizoic on other marine invertebrates and generally use specific taxa as hosts. The present study investigates the patterns of host switching and the diversification history of zoantharians based on the most comprehensive molecular phylogenetic analyses to date, using sequences from three mitochondrial and three nuclear markers from representatives of 27 of 29 genera. Our results indicate that symbiotic zoantharians, in particular those within suborder Macrocnemina, diversified through repeated host switching. In addition, colonization of new host taxa appears to have driven morphological and ecological specialization in zoantharians. These findings have important implications for understanding the role of symbioses in the morphological and ecological evolution of marine invertebrates.

The Complete Genome Sequences of 7 Species of Epizoanthus (Epizoanthidae, Zoantharia, Hexacorallia, Cnidaria)

We present the complete genome sequences of 7 species of the zoantharian genus Epizoanthus. Illumina sequencing was performed on genetic material from single wild-collected individuals. The reads were assembled using a de novo method followed by a finishing step. The raw and assembled data are publicly available via GenBank.

The Complete Genome Sequences of 13 Species of Brachycnemina (Cnidaria, Hexacorallia, Anthozoa, Zoantharia)

We present the complete genome sequences of 13 species of the zoantharian suborder Brachycnemina (Haddon, and Shackleton, 1891; Poliseno et al., 2020). Genome sequencing was performed on genetic material from single wild-collected individuals. For each species the sequence reads were assembled using a de novo method followed by a finishing step. The raw and assembled data are publicly available via GenBank.

Building consensus around the assessment and interpretation of Symbiodiniaceae diversity

Within microeukaryotes, genetic variation and functional variation sometimes accumulate more quickly than morphological differences. To understand the evolutionary history and ecology of such lineages, it is key to examine diversity at multiple levels of organization. In the dinoflagellate family Symbiodiniaceae, which can form endosymbioses with cnidarians (e.g., corals, octocorals, sea anemones, jellyfish), other marine invertebrates (e.g., sponges, molluscs, flatworms), and protists (e.g., foraminifera), molecular data have been used extensively over the past three decades to describe phenotypes and to make evolutionary and ecological inferences. Despite advances in Symbiodiniaceae genomics, a lack of consensus among researchers with respect to interpreting genetic data has slowed progress in the field and acted as a barrier to reconciling observations. Here, we identify key challenges regarding the assessment and interpretation of Symbiodiniaceae genetic diversity across three levels: species, populations, and communities. We summarize areas of agreement and highlight techniques and approaches that are broadly accepted. In areas where debate remains, we identify unresolved issues and discuss technologies and approaches that can help to fill knowledge gaps related to genetic and phenotypic diversity. We also discuss ways to stimulate progress, in particular by fostering a more inclusive and collaborative research community. We hope that this perspective will inspire and accelerate coral reef science by serving as a resource to those designing experiments, publishing research, and applying for funding related to Symbiodiniaceae and their symbiotic partnerships.

A Draft Genome Sequence of Dorometra sesokonis (Antedonidae, Comatulida, Crinoidea, Echinodermata)

We present the complete genome sequence of Dorometra sesokonis. Genome sequencing was performed on genetic material from a single wild-collected individual. The sequence reads were assembled using a de novo method followed by a finishing step. The raw and assembled data are publicly available via GenBank.

Colour patterns influence symbiosis and competition in the anemonefish-host anemone symbiosis system

Colour patterns in fish are often used as an important medium for communication. Anemonefish, characterized by specific patterns of white bars, inhabit host anemones and defend the area around an anemone as their territory. The host anemone is used not only by the anemonefish, but also by other fish species that use anemones as temporary shelters. Anemonefish may be able to identify potential competitors by their colour patterns. We first examined the colour patterns of fish using host anemones inhabited by Amphiprion ocellaris as shelter and compared them with the patterns of fish using surrounding scleractinian corals. There were no fish with bars sheltering in host anemones, although many fish with bars were found in surrounding corals. Next, two fish models, one with white bars and the other with white stripes on a black background, were presented to an A. ocellaris colony. The duration of aggressive behaviour towards the bar model was significantly longer than that towards the stripe model. We conclude that differences in aggressive behaviour by the anemonefish possibly select the colour patterns of cohabiting fish. This study indicates that colour patterns may influence not only intraspecific interactions but also interspecific interactions in coral reef ecosystems.

Shallow epifaunal sea cucumber densities and their relationship with the benthic community in the Okinawa Islands

Sea cucumbers are important ecological engineers in marine ecosystems. However, the fishery demand of some species, especially large-epifaunal and commercially used (LEC) sea cucumbers, has risen drastically, resulting in serious depletion of local populations for many species. Despite this problem, basic ecological data on sea cucumbers, such as population densities and preferred habitats, are often still insufficient. Here, we report on the population densities of multiple LEC sea cucumber species, and their ambient benthic communities at eight sites around Okinawa Islands. Further, we discuss the correspondence between sea cucumber densities and the surrounding coral communities. Our results show two sites within national or quasi-national parks, Aka and Manza, where stricter rules have been placed on fisheries and land reclamation compared to other areas, had the highest and third highest sea cucumber population densities among sites, respectively. Holothuria atra was observed at all survey sites and made up the majority of sea cucumber populations at all sites except for Chatan and Sesoko, where Holothuria leucospilota and Stichopus chloronotus were most abundant, respectively. Regarding the relationships between benthic composition and LEC sea cucumber species, S. chloronotus was significantly correlated with dead corals, scleractinian corals, and coralline algae. As well, H. leucospilota had significant correlations with rubble. Although there were no significant correlations between any specific scleractinian coral genus and sea cucumber densities, S. chloronotus was marginally insignificant with Platygyra and Psammocora. Notably, medium- to highly valued species were sparse in our surveys, and most of them appeared at only one site. Additionally, at one site (Odo), only three LEC sea cucumber individuals were observed. Combining these facts with relatively low population densities around the Okinawa Islands compared to densities reported in previous research from the Indo-West Pacific Ocean region, we conclude that Okinawan LEC sea cucumber populations have been and are being impacted by high levels of direct (e.g., overexploitation, as well as coastal development) and indirect anthropogenic pressure (e.g., decreasing water quality). To address the current situation, repeated monitoring and more detailed investigations to reveal the drivers that determine LEC sea cucumber species aggregations and population densities are urgently needed, along with more robust management of remaining LEC sea cucumber populations.

Exploring the trends of adaptation and evolution of sclerites with regards to habitat depth in sea pens

Octocorals possess sclerites, small elements comprised of calcium carbonate (CaCO₃) that are important diagnostic characters in octocoral taxonomy. Among octocorals, sea pens comprise a unique order (Pennatulacea) that live in a wide range of depths. Habitat depth is considered to be important in the diversification of octocoral species, but a lack of information on sea pens has limited studies on their adaptation and evolution across depth. Here, we aimed to reveal trends of adaptation and evolution of sclerite shapes in sea pens with regards to habitat depth via phylogenetic analyses and ancestral reconstruction analyses. Colony form of sea pens is suggested to have undergone convergent evolution and the loss of axis has occurred independently across the evolution of sea pens. Divergences of sea pen taxa and of sclerite forms are suggested to depend on habitat depths. In addition, their sclerite forms may be related to evolutionary history of the sclerite and the surrounding chemical environment as well as water temperature. Three-flanged sclerites may possess the tolerance towards the environment of the deep sea, while plate sclerites are suggested to be adapted towards shallower waters, and have evolved independently multiple times. The common ancestor form of sea pens was predicted to be deep-sea and similar to family Pseudumbellulidae in form, possessing sclerites intermediate in form to those of alcyonaceans and modern sea pens such as spindles, rods with spines, and three-flanged sclerites with serrated edges sclerites, as well as having an axis and bilateral traits.

Diversity and distribution of air-breathing sea slug genus Peronia Fleming, 1822 (Gastropoda: Onchidiidae) in southern Japanese waters

Species of the genus Peronia Fleming, 1822, are air-breathing onchidiid sea slugs that inhabit intertidal reef flats of temperate to tropical zones. In the Ryukyu Islands of southern subtropical Japan, Peronia species are a traditional food source for local people. To date, there have been three species recorded around Okinawajima Island; P. verruculata and P. peronii, along with recently described P. okinawensis, which was described as possibly endemic to Okinawajima Island. This study aimed to map the distribution ranges of these three Peronia species within the Ryukyu Islands using molecular analyses in order to understand the specific distribution of each species. Since Peronia species are generally indistinguishable by gross external morphology, a DNA barcoding approach was employed to identify specimens. The molecular data showed that there are four species present in the Ryukyu Islands. P. verruculata (unit #1 sensu Dayrat et al., 2020) was dominant at almost all locations, while P. peronii was present in much lower numbers than P. verruculata, but found across a relatively wide range in the Ryukyu Islands. We newly record P. okinawensis and P. setoensis from Amami Oshima Island and from several places around Okinawajima Island, and also identified high levels of genetic variation within P. setoensis. Peronia okinawensis and P. setoensis have been thought to be endemic to Okinawajima Island and to Honshu, mainland Japan, respectively. However, as both species were observed around Okinawajima and Amami Oshima islands, other islands of the Ryukyus are also likely to harbor these species, and their distribution ranges are wider than previously thought. Based on the results from molecular analyses, we provide general descriptions of each species. Sizes of specimens were consistently smaller for P. setoensis and relatively larger for P. peronii specimens. On the other hand, P. verruculata and P. okinawensis had similar size ranges, but P. okinawensis had comparatively much more distinct papillae. This study revealed that the Ryukyu Islands are the only region currently known with four sympatric Peronia species, and this work provides a basis for future research on these Peronia species throughout the northwest Pacific Ocean, representing the first step in more effective management of the local Peronia fisheries in the Ryukyu Islands.

Population genetics and demography of the coral-killing cyanobacteriosponge, Terpios hoshinota, in the Indo-West Pacific

The first occurrence of the cyanobacteriosponge Terpios hoshinota was reported from coral reefs in Guam in 1973, but was only formally described in 1993. Since then, the invasive behavior of this encrusting, coral-killing sponge has been observed in many coral reefs in the West Pacific. From 2015, its occurrence has expanded westward to the Indian Ocean. Although many studies have investigated the morphology, ecology, and symbiotic cyanobacteria of this sponge, little is known of its population genetics and demography. In this study, a mitochondrial cytochrome oxidase I (COI) fragment and nuclear ribosomal internal transcribed spacer 2 (ITS2) were sequenced to reveal the genetic variation of T. hoshinota collected from 11 marine ecoregions throughout the Indo-West Pacific. Both of the statistical parsimony networks based on the COI and nuclear ITS2 were dominated by a common haplotype. Pairwise F _ST and Isolation-by-distance by Mantel test of ITS2 showed moderate gene flow existed among most populations in the marine ecoregions of West Pacific, Coral Triangle, and Eastern Indian Ocean, but with a restricted gene flow between these regions and Maldives in the Central Indian Ocean. Demographic analyses of most T. hoshinota populations were consistent with the mutation-drift equilibrium, except for the Sulawesi Sea and Maldives, which showed bottlenecks following recent expansion. Our results suggest that while long-range dispersal might explain the capability of T. hoshinota to spread in the IWP, stable population demography might account for the long-term persistence of T. hoshinota outbreaks on local reefs.

A community and functional comparison of coral and reef fish assemblages between four decades of coastal urbanisation and thermal stress

Urbanized coral reefs experience anthropogenic disturbances caused by coastal development, pollution, and nutrient runoff, resulting in turbid, marginal conditions in which only certain species can persist. Mortality effects are exacerbated by increasingly regular thermal stress events, leading to shifts towards novel communities dominated by habitat generalists and species with low structural complexity.

There is limited data on the turnover processes that occur due to this convergence of anthropogenic stressors, and how novel urban ecosystems are structured both at the community and functional levels. As such, it is unclear how they will respond to future disturbance events.

Here, we examine the patterns of coral reef community change and determine whether ecosystem functions provided by specialist species are lost post‐disturbance. We present a comparison of community and functional trait‐based changes for scleractinian coral genera and reef fish species assemblages subject to coastal development, coastal modification, and mass bleaching between two time periods, 1975–1976 and 2018, in Nakagusuku Bay, Okinawa, Japan.

We observed an increase in fish habitat generalists, a dominance shift from branching to massive/sub‐massive corals and increasing site‐based coral genera richness between years. Fish and coral communities significantly reassembled, but functional trait‐based multivariate space remained constant, indicating a turnover of species with similar traits. A compression of coral habitat occurred, with shallow (<5 m) and deep (>8 m) coral genera shifting towards the mid‐depths (5–8 m).

We show that although reef species assemblages altered post disturbance, new communities retained similar ecosystem functions. This result could be linked to the stressors experienced by urban reefs, which reflect those that will occur at an increasing frequency globally in the near future. Yet, even after shifts to disturbed communities, these fully functioning reef systems may maintain high conservation value.

Large host anemones can be shelters of a diverse assemblage of fish species, not just anemonefish

The mutualistic relationships between anemonefish (Amphiprion; Pomacentridae) and host sea anemones are well known, but host anemones are also used as shelter by damselfish (Pomacentridae), wrasses (Labridae) and cardinalfish (Apogonidae). The threespot dascyllus Dascyllus trimaculatus (Pomacentridae) is known to live on or near host anemones in their immature phase. Nonetheless, detailed studies on the use of host anemones by other fish species have not yet been conducted. To understand the factors that influence the use of host anemones by other fish species, this study investigated the fish biota around host anemones in the Ryukyu Archipelago. Other than Amphiprion spp. and D. trimaculatus, 10 additional species of fish (9 species of damselfish and 1 species of cardinalfish) were confirmed to temporarily use host anemones as shelter, and five species of wrasse including Labroides dimidiatus came to clean anemonefish. Logistic regression analyses (independent variable: presence or absence of other species of fish; dependent variables: anemonefish aggressiveness, size of host anemone, number of D. trimaculatus) indicated that the size of host anemones is important for the presence of fish, both in species using the anemone as temporary shelter and in cleaner species. Large host anemones can provide shelter and food resources for other species of coral reef fish as well as for anemonefish.

Prevalence, complete genome, and metabolic potentials of a phylogenetically novel cyanobacterial symbiont in the coral-killing sponge, Terpios hoshinota

Terpios hoshinota is an aggressive, space‐competing sponge that kills various stony corals. Outbreaks of this species have led to intense damage to coral reefs in many locations. Here, the first large‐scale 16S rRNA gene survey across three oceans revealed that bacteria related to the taxa Prochloron, Endozoicomonas, SAR116, Ruegeria, and unclassified Proteobacteria were prevalent in T. hoshinota. A Prochloron‐related bacterium was the most dominant and prevalent cyanobacterium in T. hoshinota. The complete genome of this uncultivated cyanobacterium and pigment analysis demonstrated that it has phycobiliproteins and lacks chlorophyll b, which is inconsistent with the definition of Prochloron. Furthermore, the cyanobacterium was phylogenetically distinct from Prochloron, strongly suggesting that it should be a sister taxon to Prochloron. Therefore, we proposed this symbiotic cyanobacterium as a novel species under the new genus Candidatus Paraprochloron terpiosi. Comparative genomic analyses revealed that ‘Paraprochloron’ and Prochloron exhibit distinct genomic features and DNA replication machinery. We also characterized the metabolic potentials of ‘Paraprochloron terpiosi’ in carbon and nitrogen cycling and propose a model for interactions between it and T. hoshinota. This study builds a foundation for the study of the T. hoshinota microbiome and paves the way for better understanding of ecosystems involving this coral‐killing sponge.

A New Species of Sea Whip Gorgonian-Associated Zoantharian (Cnidaria: Anthozoa: Hexacorallia: Parazoanthidae) from the Ryukyu Islands, Japan, with Subgeneric Subdivision of Genus Umimayanthus

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.

Higher Genetic Diversity of the Common Sea Cucumber Holothuria (Halodeima) atra in Marine Protected Areas of the Central and Southern Ryukyu Islands

Recently, sea cucumbers (Echinodermata: Holothuroidea) have been over-exploited in many areas of the world, including in the Ryukyu Islands, southern Japan, due to increases in their economic importance. Nevertheless, management and protection of sea cucumbers are insufficient worldwide. The black sea cucumber Holothuria (Halodeima) atra Jaeger, 1833, inhabits a large range across the Indo-West Pacific Ocean and is a widely harvested species. Here we conducted population genetic analyses on H. atra using partial mitochondrial DNA sequences of cytochrome c oxidase subunit I (COI) and 16S ribosomal RNA (16S) to examine 11 different populations around three island groups in the middle Ryukyus; Okinawajima Island, the Kerama Islands, and the Sakishima Islands, all within Okinawa Prefecture. We found 27 haplotypes for COI and 16 haplotypes for 16S. Locations within national and quasi-national parks (Zamami Island, Keramas, and Manza, Okinawajima; managed by the national Ministry of Environment and Okinawa Prefecture, respectively) had the highest number of haplotypes, whereas locations with less management and more anthropogenic pressure had lower numbers The mean of all samples' genetic diversity indices was moderate with regards to both haplotype and nucleotide diversity. According to our results, Zamami Ama was the most genetically diverse location based on both markers used, likely because it is located within Kerama-Shoto National Park with comparatively stricter regulations than most other locations. Based on our COI sequences, three-quarters of the locations with the highest haplotype diversity were found to be distant from Okinawajima Island, indicating that the genetic diversity of H. atra was reduced around Okinawajima Island. Our results possibly reflect negative impacts from anthropogenic pressures such as over-harvesting and coastal development, although future comprehensive research including sequences of nuclear loci is needed to confirm this hypothesis.

Two new species of threadlike blood flukes (Aporocotylidae), with a molecular revision of the genera Ankistromeces Nolan & Cribb, 2004 and Phthinomita Nolan & Cribb, 2006

Ankistromeces Nolan & Cribb, 2004 and Phthinomita Nolan & Cribb, 2006 are sister genera of threadlike blood flukes (Trematoda: Aporocotylidae) infecting teleost fishes of the tropical Indo-west Pacific. Here, we report new collections of these genera from Australia, Indonesia, and Japan. A new species of Ankistromeces, Ankistromeces kawamurai n. sp., is described from Siganus spinus (Linnaeus) off Okinawa, Japan, and a new species of Phthinomita, Phthinomita abdita n. sp., from Choerodon cephalotes (Castelnau), in Moreton Bay, Australia; the new species are morphologically cryptic within their respective genera and are delineated by molecular and ecological data. Ankistromeces olsoni Nolan & Cribb, 2006 is reported from Siganus fuscescens (Houttuyn) off Heron Island (southern Great Barrier Reef), Lizard Island (northern Great Barrier Reef), and Okinawa and Wakayama Prefectures, Japan and from Siganus spinus (Linnaeus) from off Bali, Indonesia. Ankistromeces mariae Nolan & Cribb, 2004 is re-reported from the type-host, Meuschenia freycineti (Quoy & Gaimard), from a new location, Gypsy Bay, Tasmania. Phthinomita poulini Nolan & Cribb, 2006 is re-reported from its type-locality, Lizard Island, from a range of mullids, including five new host species, and its range is extended to include Moreton Bay. Phthinomita symplocos Nolan & Cribb, 2006 is reported from Bali and P. hallae Nolan & Cribb, 2006, P. jonesi Nolan & Cribb, 2006, P. littlewoodi Nolan & Cribb, 2006, and P. munozae Nolan & Cribb, 2006 are each re-reported from their type-host and type-localities. New cox1 mtDNA data were generated for all known species of these two genera from new and archival material. Analyses of these data enabled an evaluation of all known Phthinomita species; P. robertsthomsoni Nolan & Cribb, 2006 is synonymised with P. adlardi Nolan & Cribb, 2006, and P. brooksi Nolan & Cribb, 2006 is synonymised with P. sasali Nolan & Cribb, 2006. We highlight the failure of ITS2 data to delineate closely related aporocotylid species. In contrast, cox1 sequence data are proving reliable and effective in this context and we recommend their incorporation in future studies of blood fluke taxonomy.

A new Antipathozoanthus species (Cnidaria, Hexacorallia, Zoantharia) from the northwest Pacific Ocean

A new species of zoantharian within the genus Antipathozoanthus is described based on specimens collected from the coast of mainland Japan, northwest Pacific Ocean. Antipathozoanthustubussp. nov. is characterized by its substrate (epibiotic on polychaete tube) and habitat (exposed rock). As well, the results of molecular phylogenetic analyses using concatenated multiple genetic markers also support the distinction between A.tubussp. nov. and its congenerics. Antipathozoanthustubussp. nov. is the first species of Antipathozoanthus species reported to be epibiotic on polychaete tubes, and is the second species in the genus that is not associated with antipatharians.

Investigating Sources of Conflict in Deep Phylogenomics of Vetigastropod Snails

Phylogenetic analyses may suffer from multiple sources of error leading to conflict between genes and methods of inference. The evolutionary history of the mollusc clade Vetigastropoda makes them susceptible to these conflicts, their higher level phylogeny remaining largely unresolved. Originating over 350 Ma, vetigastropods were the dominant marine snails in the Paleozoic. Multiple extinction events and new radiations have resulted in both very long and very short branches and a large extant diversity of over 4000 species. This is the perfect setting of a hard phylogenetic question in which sources of conflict can be explored. We present 41 new transcriptomes across the diversity of vetigastropods (62 terminals total), and provide the first genomic-scale phylogeny for the group. We find that deep divergences differ from previous studies in which long branch attraction was likely pervasive. Robust results leading to changes in taxonomy include the paraphyly of the order Lepetellida and the family Tegulidae. Tectinae subfam. nov. is designated for the clade comprising Tectus, Cittarium, and Rochia. For two early divergences, topologies disagreed between concatenated analyses using site heterogeneous models versus concatenated partitioned analyses and summary coalescent methods. We investigated rate and composition heterogeneity among genes, as well as missing data by locus and by taxon, none of which had an impact on the inferred topologies. We also found no evidence for ancient introgression throughout the phylogeny. We further tested whether uninformative genes and over-partitioning were responsible for this discordance by evaluating the phylogenetic signal of individual genes using likelihood mapping, and by analyzing the most informative genes with a full multispecies coalescent (MSC) model. We find that most genes are not informative at the two conflicting nodes, but neither this nor gene-wise partitioning are the cause of discordant results. New method implementations that simultaneously integrate amino acid profile mixture models and the MSC might be necessary to resolve these and other recalcitrant nodes in the Tree of Life. [Fissurellidae; Haliotidae; likelihood mapping; multispecies coalescent; phylogenetic signal; phylogenomic conflict; site heterogeneity; Trochoidea.]

Variation on a theme: pigmentation variants and mutants of anemonefish

Pigmentation patterning systems are of great interest to understand how changes in developmental mechanisms can lead to a wide variety of patterns. These patterns are often conspicuous, but their origins remain elusive for many marine fish species. Dismantling a biological system allows a better understanding of the required components and the deciphering of how such complex systems are established and function. Valuable information can be obtained from detailed analyses and comparisons of pigmentation patterns of mutants and/or variants from normal patterns. Anemonefishes have been popular marine fish in aquaculture for many years, which has led to the isolation of several mutant lines, and in particular color alterations, that have become very popular in the pet trade. Additionally, scattered information about naturally occurring aberrant anemonefish is available on various websites and image platforms. In this review, the available information on anemonefish color pattern alterations has been gathered and compiled in order to characterize and compare different mutations. With the global picture of anemonefish mutants and variants emerging from this, such as presence or absence of certain phenotypes, information on the patterning system itself can be gained.

Zoantharian Endosymbiont Community Dynamics During a Stress Event

Coral reefs are complex ecosystems composed of many interacting species. One ecologically important group consists of zoantharians, which are closely related to reef-building corals. Like corals, zoantharians form mutualistic symbioses with dinoflagellate micro-algae (family Symbiodiniaceae), but their associations remain underexplored. To examine the degree to which zoantharians exhibit altered symbiont dynamics under changing environmental conditions, we reciprocally transplanted colonies of Zoanthus sansibaricus between intertidal (2 m) and subtidal (26 m) depths within a reef in Okinawa, Japan. At this location, Z. sansibaricus can associate with three Symbiodiniaceae species from two genera distributed along a light and depth gradient. We developed species-specific molecular assays and sampled colonies pre- and post-transplantation to analyze symbiont community diversity. Despite large environmental differences across depths, we detected few symbiont compositional changes resulting from transplantation stress. Colonies sourced from the intertidal zone associated with mixtures of a "shallow" Symbiodinium sp. and a "shallow" Cladocopium sp. independent of whether they were transplanted to shallow or deep waters. Colonies sourced from the subtidal zone were dominated by a "deep" Cladocopium sp. regardless of transplant depth. Subtidal colonies brought to shallow depths did not transition to the presumably high-light adapted shallow symbionts present in the new environment, but rather bleached and died. These patterns mirror observations of highly stable coral-algal associations subjected to depth transplantation. Our results indicate that Zoanthus-Symbiodiniaceae symbioses remain stable despite stress, suggesting these important reef community members have relatively low capacity to shuffle to more stress-tolerant micro-algae in response to ongoing climate change.

Coral cover and rubble cryptofauna abundance and diversity at outplanted reefs in Okinawa, Japan

Global climate change is leading to damage and loss of coral reef ecosystems. On subtropical Okinawa Island in southwestern Japan, the prefectural government is working on coral reef restoration by outplanting coral colonies from family Acroporidae back to reefs after initially farming colonies inside protected nurseries. In order to establish a baseline for future comparisons, in this study we documented the current status of reefs undergoing outplanting at Okinawa Island, and nearby locations where no human manipulation has occurred. We examined three sites on the coast of Onna Village on the west coast of the island; each site included an outplanted and control location. We used (1) coral rubble sampling to measure and compare abundance and diversity of rubble cryptofauna; and (2) coral reef monitoring using Line Intercept Transects to track live coral coverage. Results showed that rubble shape had a positive correlation with the numbers of animals found within rubble themselves and may therefore constitute a reliable abundance predictor. Each outplanted location did not show differences with the corresponding control location in terms of rubble cryptofauna abundance, but outplanted locations had significantly lower coral coverage. Overall, differences between sites (Maeganeku1, Maeganeku2 and Manza, each including both outplanted and control locations) were significant, for both rubble cryptofauna and coral coverage. We recommend (1) to outplant colonies from more stress-resistant genera in place of Acropora, and (2) to conduct regular surveys to monitor the situation closely. With a lack of baseline data preceding impacts, rigorous monitoring over time can highlight trends towards increases or decreases in evaluated variables, allowing to obtain a clearer idea of the effects of transplants and on the trajectory of impacts due to climate change and local stressors . Finally, we also recommend (3) to establish conservation and sustainable practices that could aid the ongoing restoration efforts such as installing anchoring buoys to reduce impacts from anchoring, which could reduce coral mortality of both outplanted and native coral colonies.

Comparison of Symbiodiniaceae diversities in different members of a Palythoa species complex (Cnidaria: Anthozoa: Zoantharia)-implications for ecological adaptations to different microhabitats

In this study we compared genotypes of zoantharian host-associating algal symbionts among Palythoa species, which are among the dominant benthic reef organisms in the Ryukyu Archipelago, Japan, and evaluated Symbiodiniaceae diversities of closely related congeneric Palythoa species. We targeted a species complex of the zoantharian genus Palythoa (P. tuberculosa, P. sp. yoron, P. mutuki) living among different microhabitats in a narrow reef area of Tokunoshima Island. For phylogenetic analyses, we used two DNA marker regions; nuclear internal transcribed spacer (ITS) and plastid mini-circle non-coding region (psbA^ncr), both of which have previously been used to determine Symbiodiniaceae genotypes of zoantharian species. Our results showed that all Palythoa species hosted symbionts of the genus Cladocopium, with genotypic compositions of this genus showing some variations among the three different Palythoa species. Additionally, we found that the Cladocopium genotypic composition was statistically different among Palythoa species, and among P. tuberculosa specimens in different microhabitats. Our results suggest that ecological divergence among these three Palythoa species may be related to differing Symbiodiniaceae diversities that may in turn contribute to eco-physiological adaptation into different microhabitats on coral reefs.

Knock knock, who's there?: marine invertebrates in tubes of Ceriantharia (Cnidaria: Anthozoa)

This study reports on the fauna found in/on tubes of 10 species of Ceriantharia and discusses the characteristics of these occurrences, as well as the use of mollusc shells in ceriantharian tube construction. A total of 22 tubes of Ceriantharia from Argentina, Brazil, Japan, Norway, Portugal and the United States were analysed, revealing 58 species of marine invertebrates using them as alternative substrates. Based on a literature review and analyses of the sampled material, we report new occurrences for Photissarae (Crustacea), Microgazarotella (Mollusca), Brada sp., Dipolydora spp., Notocirrus spp., and Syllisgarciai (Annelida). The use of mollusc shells in tube construction increases the tubes’ structural resistance and strength. Ceriantharian tubes are suitable alternative substrates for the dwelling of numerous tubicolous and infaunal species that usually burrow into sediments or anchor on fixed or mobile habitats seeking shelter, thus playing a relevant role as local biodiversity hotspots.

Global marine biodiversity in the context of achieving the Aichi Targets: ways forward and addressing data gaps

In 2010, the Conference of the Parties of the Convention on Biological Diversity agreed on the Strategic Plan for Biodiversity 2011–2020 in Aichi Prefecture, Japan. As this plan approaches its end, we discussed whether marine biodiversity and prediction studies were nearing the Aichi Targets during the 4th World Conference on Marine Biodiversity held in Montreal, Canada in June 2018. This article summarises the outcome of a five-day group discussion on how global marine biodiversity studies should be focused further to better understand the patterns of biodiversity. We discussed and reviewed seven fundamental biodiversity priorities related to nine Aichi Targets focusing on global biodiversity discovery and predictions to improve and enhance biodiversity data standards (quantity and quality), tools and techniques, spatial and temporal scale framing, and stewardship and dissemination. We discuss how identifying biodiversity knowledge gaps and promoting efforts have and will reduce such gaps, including via the use of new databases, tools and technology, and how these resources could be improved in the future. The group recognised significant progress toward Target 19 in relation to scientific knowledge, but negligible progress with regard to Targets 6 to 13 which aimed to safeguard and reduce human impacts on biodiversity.

Morphological and phylogenetic diversity of Waminoa and similar flatworms (Acoelomorpha) in the western Pacific Ocean

The genus Waminoa currently contains two described species, which each contains two types of endosymbiotic algae. Waminoa individuals are basically brown in body color, derived from these algal symbionts, and their body shape has been described as "discoid to obcordate". They have been found as associates of various anthozoans (Cnidaria) in the Indo-Pacific Ocean and the Red Sea. In order to reveal the diversity of the genus Waminoa and their hosts, we conducted phylogenetic and morphological analyses on acoelomate flatworms specimens collected from Japan, Palau and Indonesia. At least 18 Waminoa morphotypes were found on at least 20 anthozoan host species, and two specimens were found on species of two sea stars. Overall, there were two main body shapes of specimens; obcordate, as seen in W. litus and W. brickneri, and the other molar-like with an elongated body. These two body shapes each represented a separate clade in 18S rDNA and mitochondrial cytochrome c oxidase subunit 1 (COI) phylogenetic trees, with W. brickneri included in the obcordate subclade. Automatic Barcode Gap Discovery (ABGD) analyses on COI sequences of our specimens revealed the presence of at least five operational taxonomic units (OTUs). These five OTUs consisted of one large group of all obcordate animals, three OTUs consisting of one specimen each within the molar-like clade, and one large group of the remaining molar-like specimens. Both clades contain numerous morphotypes and were associated with a variety of hosts. Finally, based on genetic distances, the molar-like specimens are considered as an unnamed genus group separate from Waminoa, which needs to be clarified in future studies.

A New Epizoanthus Species (Cnidaria: Anthozoa: Epizoanthidae) Associated with the Gastropod Mollusk Guildfordia triumphans from Southern Japan

From previous research, it is known that hermit crabs predominantly dwell in vacated gastropod shells. Several epibiotic taxa are known to live on gastropod shells inhabited by hermit crabs, including some species of the zoantharian genus Epizoanthus. Although many previous taxonomic studies have focused on hermit-crab-associated Epizoanthus species, and have resulted in the description of several species, gastropod-associated species have received comparatively much less attention. At least five Epizoanthus species associated with gastropods have been formally described, but some species have not been found or examined since their original description. In Japan, specimens on the gastropod mollusk Guildfordia triumphans have been found and examined in previous studies, but no formal taxonomic conclusions were made. In this study, we formally describe Epizoanthus rinbou sp. n. from southern Japan based on molecular phylogenetic analyses combined with morphological observations. Epizoanthus rinbou sp. n. is located within an Epizoanthus clade consisting of species associated with gastropods, hermit crabs, sea urchins, and barnacles, as well as non-associated Epizoanthus species. The present study highlights the utility of molecular phylogeny for understanding the diversity and relationships of gastropod-associated Epizoanthus species.

Population Connectivity in the Common Reef Zoantharian Zoanthus sansibaricus (Anthozoa: Hexacorallia) in Southern Japan

Tropical and subtropical shallow benthic marine communities are highly diverse and balanced systems that constitute an important natural resource. Knowledge of the genetic diversity, connectivity and reproduction mode of each population is critical to understanding the fate of whole assemblages in times of disturbances. Importantly, the capability of populations to adapt to environmental challenges will be crucial to determining their survival. Here, we report on the population structure of the common reef zoantharian Zoanthus sansibaricus in the northwestern Pacific, by examining populations at three different locations in southern Japan using five highly variable microsatellite markers. Analyses of a population at the species' northern distribution limit combined with analyses of two subtropical populations suggest that habitat characteristics and ocean currents influence the connectivity and genetic diversity of this species. Our findings emphasize the adaptive ability of Z. sansibaricus to different environmental conditions and may help explain the wide distribution and generalist nature of this species.

Marine biodiversity research in the Ryukyu Islands, Japan: current status and trends

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.

Molecular phylogeny and diversity of sea pens (Cnidaria: Octocorallia: Pennatulacea) with a focus on shallow water species of the northwestern Pacific Ocean

The order Pennatulacea, commonly known as sea pens, are colony-forming benthos belonging within subclass Octocorallia (Anthozoa, Cnidaria). Sea pens are found worldwide from shallow to deep waters, and they are important components in sandy and muddy environments. Thus far, there has been only one molecular study focusing on the phylogenetic relationships within the order Pennatulacea, which mainly treated deep-sea species, and thus information on shallow water species is still lacking. On a regional scale, the diversity of sea pens in the northwestern Pacific, including Japan and Palau, has not been well investigated. In this research, we aimed to: (1) more accurately resolve the phylogenetic relationships of sea pens with the inclusion of shallow water species, and (2) obtain a better understanding of the diversity of sea pens in Japan and Palau. Specimens were collected by SCUBA and dredging from the Ryukyu Islands in southern Japan, and from mainland Japan and Palau, and identified to at least the genus level by their morphological traits. Construction of phylogenetic trees with concatenated sequences including the mitochondrial mutS-like protein DNA mismatch repair gene mtMutS and the NADH dehydrogenase subunit 2 ND2 region were performed. The p-distances of mtMutS were calculated for estimation of species number following McFadden et al. (2011). Molecular data for 12 families and 20 genera of sea pens were used in this study. This most comprehensive study including shallow water taxa provided us with more knowledge of phylogenetic relationships. The resulting phylogenetic trees showed a topology distinguished by four large clades (clades 1-4). Families Veretillidae and Echinoptilidae are shown as not the earliest-diverging taxa. Virgulariidae and Scleroptilidae are shown as polyphyletic groups, and our results reconfirm that families Pennatulidae, Kophobelemnidae and Umbellulidae are not monophyletic groups. Overall, we collected and examined an estimated 18 species from the Ryukyu Islands, 16 species from mainland Japan, and five species from Palau. Some of these specimens represented new records from Ryukyu Islands and Palau. Previous records of these sea pens did not exist likely due to a lack of diversity research in sandy and muddy areas. These results demonstrate that many sea pens discoveries likely remain in shallow waters of the Pacific.

Appearance of an anomalous black band disease at upper mesophotic depths after coral bleaching

In the summer of 2016, extensive coral bleaching occurred on the coral reefs of Okinawa, Japan, which was often lethal in shallow waters. In November 2016, after the coral bleaching event, an anomalous black band disease (ABBD) was noticed during regular monitoring of the Pachyseris-dominated upper mesophotic Ryugu Reef in Okinawa. We subsequently conducted 10 × 1 m belt transects in deeper (30-35 m depth, n = 5) and shallower areas (27-29 m, n = 7) of the reef and obtained data on coral percentage coverage, Pachyseris percentage coverage, occurrence (numbers of lesions) of ABBD, and ABBD percentage coverage on Pachyseris. Both depths showed high live coral coverage (>90%), indicating little mortality from the summer 2016 bleaching event, and Pachyseris percentage coverage was significantly higher in the deeper area (mean ± SD = 48.6 ± 45.0%) compared to the shallower area (5.1 ± 5.0%). Additionally, although numbers of ABBD occurrences (= lesions) were significantly higher in the deeper area (81.0 ± 52.8 as opposed to 8.3 ± 6.7 at shallower depths), total ABBD percentage coverage on Pachyseris was not significantly different between shallow and deep areas (7.0 ± 3.2% versus 4.7 ± 3.6%). ABBD was observed to be Pachyseris-specific at Ryugu Reef. These results indicate that similar to shallower reefs, mesophotic reefs can experience increased disease occurrences subsequent to non-lethal coral bleaching events.

A phylogeny and the evolution of epizoism within the family Hydrozoanthidae with description of a new genus and two new species

The Family Hydrozoanthidae are macrocnemic zoantharians, however their phylogenetic position is closer to brachycnemic zoantharians than to other macrocnemic zoantharians. Previous studies have indicated the presence of undescribed Hydrozoanthidae species from various locations in the Indo-Pacific Ocean. In this study, two new Hydrozoanthidae species, Aenigmanthus segoi gen. n., sp. n. and Hydrozoanthus sils sp. n., are described from Japanese and Palauan waters based on combined morphological and molecular phylogenetic analyses utilizing multiple genetic markers. Additionally, Hydrozoanthidae consists of species with an obligate epizoic relationship with hydroids (Hydrozoanthus) and of species with facultative epizoic relationships (Aenigmanthus gen. n. and Terrazoanthus). Results of ancestral state reconstruction analyses indicate that Hydrozoanthus gained obligate epizoic relationships in their evolutionary history perhaps due to structural differences of host invertebrates.

Stolonifera from shallow waters in the north-western Pacific: a description of a new genus and two new species within the Arulidae (Anthozoa, Octocorallia)

A new genus and two new species of stoloniferous octocorals (Alcyonacea) within the family Arulidae are described based on specimens collected from Okinawa (Japan), Palau and Dongsha Atoll (Taiwan). Hana gen. n. is erected within Arulidae. Hanahanagasa sp. n. is characterised by large spindle-like table-radiates and Hanahanataba sp. n. is characterised by having ornamented rods. The distinction of these new taxa is also supported by molecular phylogenetic analyses. The support values resulting from maximum likelihood and Bayesian inference analyses for the genus Hana and new species H.hanagasa and H.hanataba are 82/1.0, 97/1.0 and 61/0.98, respectively. Hanahanagasa sp. n. and Hanahanataba sp. n. are the first arulid records for Okinawa, Palau, and Dongsha Atoll, and represent species of the second genus within the family Arulidae.

Systematic Revision of Symbiodiniaceae Highlights the Antiquity and Diversity of Coral Endosymbionts

The advent of molecular data has transformed the science of organizing and studying life on Earth. Genetics-based evidence provides fundamental insights into the diversity, ecology, and origins of many biological systems, including the mutualisms between metazoan hosts and their micro-algal partners. A well-known example is the dinoflagellate endosymbionts ("zooxanthellae") that power the growth of stony corals and coral reef ecosystems. Once assumed to encompass a single panmictic species, genetic evidence has revealed a divergent and rich diversity within the zooxanthella genus Symbiodinium. Despite decades of reporting on the significance of this diversity, the formal systematics of these eukaryotic microbes have not kept pace, and a major revision is long overdue. With the consideration of molecular, morphological, physiological, and ecological data, we propose that evolutionarily divergent Symbiodinium "clades" are equivalent to genera in the family Symbiodiniaceae, and we provide formal descriptions for seven of them. Additionally, we recalibrate the molecular clock for the group and amend the date for the earliest diversification of this family to the middle of the Mesozoic Era (∼160 mya). This timing corresponds with the adaptive radiation of analogs to modern shallow-water stony corals during the Jurassic Period and connects the rise of these symbiotic dinoflagellates with the emergence and evolutionary success of reef-building corals. This improved framework acknowledges the Symbiodiniaceae's long evolutionary history while filling a pronounced taxonomic gap. Its adoption will facilitate scientific dialog and future research on the physiology, ecology, and evolution of these important micro-algae.

Rafting in Zoantharia: a hitchhiker's guide to dispersal?

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.

Three new species and the molecular phylogeny of Antipathozoanthus from the Indo-Pacific Ocean (Anthozoa, Hexacorallia, Zoantharia)

In this study, three new species of macrocnemic zoantharians (Hexacorallia, Zoantharia) are described from localities in the Indo-Pacific Ocean including the Red Sea, the Maldives, Palau, and southern Japan: Antipathozoanthus obscurussp. n., A. remengesauisp. n., and A. cavernussp. n. Although the genus Antipathozoanthus is currently restricted to species living on antipatharians, A. obscurussp. n. is not associated with any living substrate and instead is found on coral reef carbonate substrate within narrow caves or cracks. The two new species that have association with antipatharians, A. remengesauisp. n. and A. cavernussp. n., can be distinguished by their relative coenenchyme development and the antipatharian species that each uses as substrate. Additionally, all new species described in this study have unique nuclear internal transcribed spacer region of ribosomal DNA (ITS-rDNA) sequences. Our results indicate that more phylogenetic studies focusing on increasing the numbers of species examined within each of the genera of Parazoanthidae are required in order to better understand the evolutionary history of substrate specificity within the family Parazoanthidae.

A preliminary survey of zoantharian endosymbionts shows high genetic variation over small geographic scales on Okinawa-jima Island, Japan

Symbiotic dinoflagellates (genus Symbiodinium) shape the responses of their host reef organisms to environmental variability and climate change. To date, the biogeography of Symbiodinium has been investigated primarily through phylogenetic analyses of the ribosomal internal transcribed spacer 2 region. Although the marker can approximate species-level diversity, recent work has demonstrated that faster-evolving genes can resolve otherwise hidden species and population lineages, and that this diversity is often distributed over much finer geographical and environmental scales than previously recognized. Here, we use the noncoding region of the chloroplast psbA gene (psbA^ncr) to examine genetic diversity among clade C Symbiodinium associating with the common reef zoantharian Palythoa tuberculosa on Okinawa-jima Island, Japan. We identify four closely related Symbiodinium psbA^ncr lineages including one common generalist and two potential specialists that appear to be associated with particular microhabitats. The sea surface temperature differences that distinguish these habitats are smaller than those usually investigated, suggesting that future biogeographic surveys of Symbiodinium should incorporate fine scale environmental information as well as fine scale molecular data to accurately determine species diversity and their distributions.

The order Zoantharia Rafinesque, 1815 (Cnidaria, Anthozoa: Hexacorallia): supraspecific classification and nomenclature

Many supraspecific zoantharian names have long and complicated histories. The present list is provided to advise researchers on the current state of supraspecific nomenclature of the zoantharians, particularly given the recent attention paid to the taxonomy, phylogeny, and biodiversity of this order. At the same time, several taxonomic issues brought to light by recent research are resolved. Details on the taxonomic and nomenclatural history of most groups are provided, along with appendices of invalid supraspecific names.