Seadragons are charismatic fishes endemic to Australia’s Great Southern Reef and are flagships for marine biodiversity. Due to their unique appearances and behaviors, seadragons are of interest for both scientific research and broader conservation purposes. However, studies on wild seadragon populations are challenging to implement, and peer-reviewed data on population demographics, life histories, and other aspects of seadragon biology and ecology are currently limited. Seadragon habitats, including kelp-covered reefs and seagrass meadows, have declined in various areas of the southern Australian coast, spurring concerns that seadragon abundances may also be contracting. The lack of range-wide baseline data on seadragon populations has precluded a robust understanding of their vulnerability to extinction, and further conservation-focused research has been recommended by past studies. Here, we summarize existing research on the three known seadragon species: common, leafy, and ruby seadragons, with the aim of improving future conservation outcomes for seadragons. Range-wide population size estimates and trends in abundance data are key knowledge gaps preventing accurate extinction risk assessments. Lack of data about basic ecological and biological factors such as longevity and reproduction further hinder effective conservation actions. We describe developing research methodologies including citizen science, machine learning, habitat mapping, and molecular methods that show promise for improving outcomes for these iconic fishes and the habitats they rely on.

This study provides an updated molecular phylogeny of Iphitime Marenzeller, 1902 (Annelida: Dorvilleidae), a group of symbiotic dorvilleid polychaetes, including a topotypic specimen of the type species, Iphitime doederleini Marenzeller, 1902. Also, a new species, Iphitime nubila sp. nov., was found associated with hermit crab hosts during a faunal survey off Shirahama, Wakayama, Japan, and is described here. Specimens of Iphitime were also found from southern California that were from the gill chambers of two different hosts of brachyuran crabs and are referrable to Iphitime loxorhynchi Hartman, 1952. The study includes morphological descriptions, ecological observations, molecular phylogenetic analyses, and ancestral state reconstruction highlighting at least two independent host switching in Iphitime. Additionally, we present the first mitochondrial genome for Iphitime, comparing its protein-coding gene order with Ophryotrocha Claparède & Mecznikow, 1869 and Veneriserva Rossi, 1984, revealing a conserved gene order within the Iphitime + Veneriserva clade. The conserved order between these two symbiotic genera contrasts with the high variation observed among several dorvilleid species. ZooBank: urn:lsid:zoobank.org:pub:8F472388-4B75-4F6F-A8B9-EE25B69CAFAC

Phylogenetic clock models translate inferred amounts of evolutionary change (calculated from either genotypes or phenotypes) into estimates of elapsed time, providing a mechanism for time scaling phylogenetic trees. Relaxed clock models, which accommodate variation in evolutionary rates across branches, are one of the main components of Bayesian dating, yet their consequences for total-evidence phylogenetics have not been thoroughly explored. Here, we combine morphological, molecular (both transcriptomic and Sanger-sequenced), and stratigraphic datasets for all major lineages of echinoids (sea urchins, heart urchins, sand dollars). We then perform total-evidence dated inference under the fossilized birth-death prior, varying two analytical conditions: the choice between autocorrelated and uncorrelated relaxed clocks, which enforce (or not) evolutionary rate inheritance; and the ability to recover ancestor-descendant relationships. Our results show that the latter has no impact on either topology or node ages and highlight a previously unnoticed interaction between the tree and clock models, with analyses implementing an autocorrelated clock precluding the recovery of direct ancestry. On the other hand, tree topology, fossil placement, divergence times, and downstream macroevolutionary inferences (e.g., ancestral state reconstructions) in sea urchins are all strongly affected by the type of relaxed clock implemented. In regions of the tree where molecular rate variation is pervasive and morphological signal relatively uninformative, fossil tips seem to play little to no role in informing divergence times, and instead passively move in and out of clades depending on the ages imposed upon them by molecular data. Our results highlight the extent to which the phylogenetic and macroevolutionary conclusions of total-evidence dated analyses are contingent on the choice of relaxed clock model, highlighting the need for either careful methodological validation or a thorough assessment of sensitivity. Our efforts continue to illuminate the echinoid tree of life, supporting the erection of the order-level clade Apatopygoida to include three living species last sharing a common ancestor with other extant lineages in the Jurassic. Furthermore, they also illustrate how the phylogenetic placement of extinct clades hinges upon the modelling of molecular data, evidencing the extent to which the fossil record remains subservient to phylogenomics. ### Competing Interest Statement The authors have declared no competing interest.

The feather star Capillaster AH Clark, 1909 (Crinoidea, Comatulidae) is a common feather star on coral reefs of the entire Indo-West Pacific region ranging from the Red Sea in the west to reefs of the central Pacific. Extensive studies of crinoids from the 1970s to 2000s by SCUBA diving encountered Capillaster, identified as C. multiradiatus (L., 1758) on reefs in the Palau Islands, Micronesia, and around Lizard Island (northern Great Barrier Reef [GBR], central GBR reefs (Rib Reef, John Brewer Reef, Davies Reef), reefs at Heron Island (southern GBR), and other sites within the Coral Triangle of the Ind-West Pacific. At Lizard Island and some other GBR reefs, two morphotypes co-occur in close proximity, both identified as C. multiradiatus using existing taxonomic keys, one collected by SCUBA during daytime dives when the crinoids were fully exposed and forming feeding postures and the other emergent and forming a filtration fan only at night on the same reefs where the other form occurred. The Palau form was collected exclusively when emergent at night and forming a feeding fan. Molecular genetic analysis using cytochrome oxidase c subunit I (COI) shows that the Palau crinoids cluster with the nocturnally emergent Capillaster at GBR. Diurnally emergent Capillaster at GBR sites are distinct in COI analysis from sympatric nocturnally emergent specimens and also in newly recognized skeletal morphologic characters and distinct color variation. We utilize molecular genetic data, traditional skeletal morphology, coloration, along with differences in emergence and feeding habits to describe a new species, Capillaster crypticus sp. nov.,which is currently known from Palau reefs and GBR reefs. A single specimen collected in daytime at Raja Ampat, Indonesia, clustered with C. crypticus on COI yet we could not confirm whether it lacks the indentation in the center of the centrodorsal. This new species represents another example of “hidden diversity” among the species-rich feather star crinoid faunas of the Indo-West Pacific region. Our data emphasize the importance of utilizing all available data: genetic, skeletal morphologic, color and pattern, ecologic, behavioral, and reproductive in distinction of crinoid species.

Introductions of non-native species threaten global biodiversity, particularly in freshwater ecosystems. Ballast water from ships is a significant pathway for them, impacting regions like the La Plata River basin. This study documents the newly reported presence of the invasive brackish/freshwater sabellid polychaetes Laonome xeprovala in the Paraná River. The Paraná River, South America’s second-largest river, features a primary channel and numerous secondary channels, with about 40

The genus Typhlonida Macpherson & Baba in Machordom et al. 2022 is a group of munidid squat lobsters typically found in deep waters. This study describes and illustrates a new species, Typhlonida cocoensis sp. nov. , from a seamount area in the eastern Pacific. Typhlonida cocoensis sp. nov. is closely related to T. sanctipauli (Henderson, 1885) but can be readily distinguished from the latter by its relatively small eyes, narrow anterior margin of the thoracic sternite 4, lack of granules on the lateral surfaces of sternite 7, and unarmed anterior branchial regions dorsally. In addition to morphological comparisons, genetic distance and phylogenetic analyses were used to support the recognition of this new species. The phylogenetic positions of the Typhlonida and Antillimunida species from the eastern Pacific are discussed.

Mitochondrial genomes of Scotoplanes clarki and Protelpidia murrayi are presented, each with 13 protein coding genes, two rRNA genes, and 22 tRNA genes. That of Scotoplanes clarki has 15,909 base pairs and that of Protelpidia murrayi is 15,896 base pairs. There is a suspected tandem repeat region of undetermined length in the assemblies of both Scotoplanes clarki and Protelpidia murrayi. The gene order of both mitogenomes is identical to that of other Elasipodida. Phylogenetic analysis revealed that Protelpidia murrayi lies within the Scotoplanes clade, suggesting that Scotoplanes is paraphyletic. Sequencing of the type species, Scotoplanes globosa, is needed to confirm if Protelpidia murrayi should be renamed as Scotoplanes murrayi.

Industrial waste barrels were discarded from 1947 to 1961 at a DDT dumpsite in the San Pedro Basin (SPB) in southern California, USA at -890 m. The barrels were studied for effects on sediment concentrations of DDX, PCBs, PAHs and sediment properties, and on benthic macrofaunal assemblages, including metazoan meiofaunal taxa >0.3 mm. DDX concentration was highest in the 2-6 cm fraction of the 10-cm deep cores studied but exhibited no correlation with macrofaunal density, composition or diversity. Macrofaunal diversity was lowest and distinct in sediments within discolored halos surrounding the barrels. Low macrobenthos density and diversity, high dominance by Entoprocta, and numerical prevalence of large nematodes may result from the very low oxygen concentrations in bottom waters (< 4.4 mu M). There is potential for macrofauna to remobilize DDX into the water column and ultimately the food web in the SPB.

Pilargidae is a family of free-living and burrowing marine annelids. A lack of available molecular data for most of these species has precluded a molecular assessment of their phylogenetic relationships and has left uncertain the placement of Antonbruunia, which is hypothesized to be either a member of Pilargidae or its sister clade, the monotypic family Antonbruunidae. In this study, we describe the new species Antonbruunia milenae sp. nov., found at 845 m of depth off the coast of San Diego, California, USA, and we address the phylogeny of these organisms using 15 novel mitogenomes and multiple Sanger-sequenced loci. Our results show that Antonbruunia falls within Pilargidae, making Antonbruunidae a junior synonym of Pilargidae. Glyphohesione was transferred from Pilarginae to Synelminae, the previously unassigned genera Otopsis and Antonbruunia were shown to belong within Synelminae, and Hermundura was assigned to Phyllodocida incertae sedis. Sigambra was found to be non-monophyletic. Four different mitogenome gene orders were found among Pilargidae. Changes between the gene orders and the ancestral state gene order of the family were inferred. Two species have introns within the COI gene. These efforts represent a significant expansion of the available molecular resources for pilargids, as well as the basis for a more stable taxonomy.

We present the mitochondrial genome of the deep-sea, epibenthic, irregular echinoid Echinocrepis rostrata, representing the first sequenced mitogenome of the order Holasteroida. The length of the complete E. rostrata mitochondrial genome is 15,716 base pairs, and its GC content is 34.87%. It contains 13 protein-coding genes, two rRNA genes, and 22 tRNA genes, whose order is identical to that of all other available echinoid mitogenomes. Phylogenetic analysis of available mitochondrial genomes, based on all coding loci, places E. rostrata as the sister group to spatangoids (heart urchins).

We describe a new species of Loimia, from shallow waters off Northern Papua New Guinea and compare morphologically to other species recorded from the region and a key is provided. We provide a Maximum likelihood tree for species of Loimia for which we have data and it forms a distinct clade from other species. Finally, we discuss characters that we consider as useful specific characters in this large genus, which includes many poorly described species.

We present the mitochondrial genome of the deep-sea, epibenthic, irregular echinoid Echinocrepis rostrata, representing the first sequenced mitogenome of the order Holasteroida. The length of the complete E. rostrata mitochondrial genome is 15,716 base pairs, and its GC content is 34.87%. It contains 13 protein-coding genes, two rRNA genes, and 22 tRNA genes, whose order is identical to that of all other available echinoid mitogenomes. Phylogenetic analysis of available mitochondrial genomes, based on all coding loci, places E. rostrata as the sister group to spatangoids (heart urchins).

Osedax is now known to be distributed around the world with more than 30 named and undescribed species. Here we report the discovery of four new species from two localities: Osedax bozoi n. sp. and Osedax craigmcclaini n. sp. from the Gulf of Mexico and Osedax estcourti n. sp. and Osedax traceyae n. sp. from off New Zealand. Osedax bozoi n. sp., Osedax estcourti n. sp., and Osedax traceyae n. sp. belong to Clade II within Osedax, one of the nude palp or apinnulate clades. Osedax craigmcclaini n. sp. belongs to the pinnulate palp Clade V. This study relies primarily on phylogenetic analysis, with some morphological analysis. Genetic data clearly show that the four new species are distinctive from their closest Osedax relatives. Two of the new species were found from less than 400 m depth, and incidences of shallower water Osedax in Clade II are shown here for the first time.

This study presents a comprehensive taxonomic revision of the family Suberitidae (Porifera: Demospongiae) for California, USA. We include the three species previously known from the region, document two additional species previously known from other regions, and formally describe four new species as Pseudosuberites latke sp. nov., Suberites californiana sp. nov., Suberites kumeyaay sp. nov., and Suberites agaricus sp. nov. Multi-locus DNA sequence data is presented for seven of the nine species, and was combined with all publicly available data to produce the most comprehensive global phylogeny for the family to date. By integrating morphological and genetic data, we show that morphological characters may be sufficient for regional species identification but are likely inadequate for global classification into genera that reflect the evolutionary history of the family. We therefore propose that DNA sequencing is a critical component to support future taxonomic revisions.

Within Polynoidae, a diverse aphroditiform family, the subfamily Macellicephalinae comprises anchialine cave-dwelling and deep-sea scaleworms. In this study, Lepidonotopodinae is synonymized with Macellicephalinae, and the tribe Lepidonotopodini is applied to a well-supported clade inhabiting deep-sea chemosynthetic-based ecosystems. Newly sequenced “genome skimming” data for 30 deep-sea polynoids and the comparatively shallow living Eulagisca gigantea is used to bioinformatically assemble their mitogenomes. When analyzed with existing scaleworm mitogenomes, deep-sea scaleworms exhibit increased gene order rearrangement events compared to shallow-water relatives. Additionally, comparative analyses of shallow-water vs. deep-sea polynoid substitution rates in mitochondrial protein-coding genes show an overall relaxed purifying selection and a positive selection of several amino acid sites in deep-sea species, indicating that polynoid mitogenomes have undergone selective pressure to evolve metabolic adaptations suited to deep-sea environments. Furthermore, the inclusion of skimming data for already known Lepidonotopodini species allowed for an increased coverage of DNA data and a representation of the taxa necessary to create a more robust phylogeny using 18 genes, as opposed to the six genes previously used. The phylogenetic results support the erection of Cladopolynoe gen. nov., Mamiwata gen. nov., Photinopolynoe gen. nov., Stratigos gen. nov., and Themis gen. nov., and emended diagnoses for Branchinotogluma, Branchipolynoe, Lepidonotopodium, and Levensteiniella.

AbstractWe present the mitochondrial genome of the deep-sea, epibenthic, irregular echinoid Echinocrepis rostrata, representing the first sequenced mitogenome of the order Holasteroida. The length of the complete E. rostrata mitochondrial genome is 15,716 base pairs, and its GC content is 34.87%. It contains 13 protein-coding genes, two rRNA genes, and 22 tRNA genes, whose order is identical to that of all other available echinoid mitogenomes. Phylogenetic analysis of available mitochondrial genomes, based on all coding loci, places E. rostrata as the sister group to spatangoids (heart urchins).

Endoparasitic annelids living inside another annelid host are known, particularly with regard to Oenonidae, but in general are poorly studied. The dorvilleid Veneriserva pygoclava is known from southern California, and its genus name (Latin = Venus’s servant) alludes to the close association with the host aphroditid scaleworm Aphrodita longipalpa . Little is known on fundamental questions on the biology of Veneriserva pygoclava . What is its mode of reproduction? How do they feed? How do they penetrate the host? We have studied multiple parasitized hosts and V. pygoclava specimens, using an integrative approach, combining µCT, histology, and electron microscopy. 3D reconstructions from µCT data of a parasitized Aphrodita show the exact position of the parasites in their natural condition within the host’s coelomic cavity. Ultrastructural investigations of the parasites revealed interesting adaptations to their lifestyle such as the complete reduction of their gut, despite the presence of a functional jaw apparatus and a modified epidermis enabling nutrient uptake from the host’s coelomic fluid. In addition to these, we also investigated spermatogenesis and oogenesis in V. pygoclava . Sperm morphology indicates an external fertilization of eggs within the coelomic cavity of the host. Mature male and female parasites living inside the same mature host and the presence of juvenile V. pygoclava within juveniles of Aphrodita suggest an obligate form of parasitism with a very early penetration of the hosts. In addition to our detailed morphological investigation, we conducted a phylogenetic analysis showing the position of Veneriserva within Dorvilleidae and its position was recovered nested among taxa of the Iphitime . Our phylogenetic analyses also show that the taxation Ophryotrocha puerilis siberti should be given full species rank and referred to as Ophryotrocha siberti . Finally, we publish here the full mitochondrial genome of V. pygoclava and discuss its novel gene order with reference to other annelids.

Mitochondrial genomes of Scotoplanes clarki and Protelpidia murrayi are presented, each with 13 protein coding genes, two rRNA genes, and 22 tRNA genes. That of Scotoplanes clarki has 15,909 base pairs and that of Protelpidia murrayi is 15,896 base pairs. There is a suspected tandem repeat region of undetermined length in the assemblies of both Scotoplanes clarki and Protelpidia murrayi. The gene order of both mitogenomes is identical to that of other Elasipodida. Phylogenetic analysis revealed that Protelpidia murrayi lies within the Scotoplanes clade, suggesting that Scotoplanes is paraphyletic. Sequencing of the type species, Scotoplanes globosa, is needed to confirm if Protelpidia murrayi should be renamed as Scotoplanes murrayi.