Systematics of Himerometra (Echinodermata: Crinoidea: Himerometridae) based on morphology and molecular data

One of the most common genera of feather stars found on tropical Indo-western Pacific reefs, Himerometra A.H.Clark, 1907, has previously included six accepted species, distinguished chiefly by variations in the enlarged proximal pinnules. This study examined new and existing specimens using molecular (mtDNA and nuDNA) techniques and morphological characters to revise the genus. Both approaches support placing H. magnipinna and H. martensi as junior synonyms of H. robustipinna. Sequence data for specimens attributed to H. bartschi also place this species as a junior synonym of H. robustipinna, despite some morphological disparity. Himerometra sol is retained as distinct despite morphological congruence with H. robustipinna, because the two known specimens were collected outside the known range of the latter, with no molecular data currently available. Himerometra persica is herein transferred to Heterometra: the type specimens were incorrectly identified. The species treated as valid are redescribed. This study illustrates the importance of re-examining crinoid species boundaries for established taxa without molecular corroboration and demonstrates that diversity in this particular feather star clade might be lower than previously thought

A Revision of the Deep-Sea Genus Axiokebuita Pocklington and Fournier, 1987 (Annelida: Scalibregmatidae)

[Abstract] The deep-sea genus Axiokebuita (Annelida, Scalibregmatidae) has hitherto been considered to contain two species, Axiokebuita minuta (Hartman, 1967) and Axiokebuita millsi Pocklington and Fournier, 1987, each rarely recorded in the literature and both supposedly having bipolar distributions. From the study of some types, other museum collection material, plus newly collected specimens from the slope depths of the Bellingshausen Sea and off the Antarctic Peninsula (Antarctica), Iceland and Iberian Peninsula, as well as from hydrothermal vents of the southeastern Pacific Ocean, the taxonomic history of the genus is revisited. Based on the results of this study, the features traditionally used to distinguish between the two species are actually the same in both. Therefore, A. millsi is proposed to be synonymised with A. minuta, which is redescribed and considered the only valid species of the genus, leaving Axiokebuita monotypic. Two previously unnoticed body sensory structures, i.e. a ciliated neck organ and a prostomial depression, were observed under scanning electron microscopy.United States. National Science Foundation; OCE- 0241613United States. National Science Foundation; OCE-0350554Ministerio de Educación y Ciencia; GLC2004–01856/AN

The Genera and Species of Comatulidae (Comatulida: Crinoidea): Taxonomic Revisions and a Molecular and Morphological Guide

We provide a guide for identification of Comatulidae, a family of crinoid echinoderms, incorporating morphological and molecular evidence. A non-dichotomous key for all genera is included, as well as photographs of species most likely to be encountered in the tropical western Pacific Ocean. Based on sequencing of cytochrome oxidase subunit I (COI), and other genes when necessary, we identified four cases where taxonomic revision was needed. We synonymized Comaster nobilis under Comaster schlegelii, and Clarkcomanthus exilis under Clarkcomanthus comanthipinnus, and re-described Clarkcomanthus albinotus. We also showed the variation of COI sequences within and among species, which varies from lineage to lineage. In some cases, specimens with obvious morphological disparity possessed very little intraspecific molecular diversity (\u3c1%). In others, specimens with nearly identical external appearances exhibited quite divergent COI sequences (up to 6%). These results, combined with the non-dichotomous key herein, offer guidelines for identification and discussion of existing and new species of Comatulidae

Neural reconstruction of bone-eating <i>Osedax</i> spp. (Annelida) and evolution of the siboglinid nervous system

BACKGROUND: Bone-devouring Osedax worms were described over a decade ago from deep-sea whale falls. The gutless females (and in one species also the males) have a unique root system that penetrates the bone and nourishes them via endosymbiotic bacteria. Emerging from the bone is a cylindrical trunk, which is enclosed in a transparent tube, that generally gives rise to a plume of four palps (or tentacles). In most Osedax species, dwarf males gather in harems along the female’s trunk and the nervous system of these microscopic forms has been described in detail. Here, the nervous system of bone-eating Osedax forms are described for the first time, allowing for hypotheses on how the abberant ventral brain and nervous system of Siboglinidae may have evolved from a ganglionated nervous system with a dorsal brain, as seen in most extant annelids. RESULTS: The intraepidermal nervous systems of four female Osedax spp. and the bone-eating O. priapus male were reconstructed in detail by a combination of immunocytochemistry, CLSM, histology and TEM. They all showed a simple nervous system composed of an anterior ventral brain, connected with anteriorly directed paired palp and gonoduct nerves, and four main pairs of posteriorly directed longitudinal nerves (2 ventral, 2 ventrolateral, 2 sets of dorso-lateral, 2 dorsal). Transverse peripheral nerves surround the trunk, ovisac and root system. The nervous system of Osedax resembles that of other siboglinids, though possibly presenting additional lateral and dorsal longitudinal nerves. It differs from most Sedentaria in the presence of an intraepidermal ventral brain, rather than a subepidermal dorsal brain, and by having an intraepidermal nerve cord with several plexi and up to three main commissures along the elongated trunk, which may comprise two indistinct segments. CONCLUSIONS: Osedax shows closer neuroarchitectural resemblance to Vestimentifera + Sclerolinum (= Monilifera) than to Frenulata. The intraepidermal nervous system with widely separated nerve cords, double brain commissures, double palp nerves and other traits found in Osedax can all be traced to represent ancestral states of Siboglinidae. A broader comparison of the nervous system and body regions across Osedax and other siboglinids allows for a reinterpretation of the anterior body region in the group

A remarkable diversity of bone-eating worms (Osedax; Siboglinidae; Annelida)

<p>Abstract</p> <p>Background</p> <p>Bone-eating <it>Osedax </it>worms have proved to be surprisingly diverse and widespread. Including the initial description of this genus in 2004, five species that live at depths between 25 and 3,000 m in the eastern and western Pacific and in the north Atlantic have been named to date. Here, we provide molecular and morphological evidence for 12 additional evolutionary lineages from Monterey Bay, California. To assess their phylogenetic relationships and possible status as new undescribed species, we examined DNA sequences from two mitochondrial (<it>COI </it>and <it>16S </it>rRNA) and three nuclear genes (<it>H3</it>, <it>18S </it>and <it>28S </it>rRNA).</p> <p>Results</p> <p>Phylogenetic analyses identified 17 distinct evolutionary lineages. Levels of sequence divergence among the undescribed lineages were similar to those found among the named species. The 17 lineages clustered into five well-supported clades that also differed for a number of key morphological traits. Attempts to determine the evolutionary age of <it>Osedax </it>depended on prior assumptions about nucleotide substitution rates. According to one scenario involving a molecular clock calibrated for shallow marine invertebrates, <it>Osedax </it>split from its siboglinid relatives about 45 million years ago when archeocete cetaceans first appeared and then diversified during the late Oligocene and early Miocene when toothed and baleen whales appeared. Alternatively, the use of a slower clock calibrated for deep-sea annelids suggested that <it>Osedax </it>split from its siboglinid relatives during the Cretaceous and began to diversify during the Early Paleocene, at least 20 million years before the origin of large marine mammals.</p> <p>Conclusion</p> <p>To help resolve uncertainties about the evolutionary age of <it>Osedax</it>, we suggest that the fossilized bones from Cretaceous marine reptiles and late Oligocene cetaceans be examined for possible trace fossils left by <it>Osedax </it>roots. Regardless of the outcome, the present molecular evidence for strong phylogenetic concordance across five separate genes suggests that the undescribed <it>Osedax </it>lineages comprise evolutionarily significant units that have been separate from one another for many millions of years. These data coupled with ongoing morphological analyses provide a solid foundation for their future descriptions as new species.</p

A newly discovered radiation of endoparasitic gastropods and their coevolution with asteroid hosts in Antarctica

Funding Funding for this research comes from the Antarctic Circumnavigation Expedition, The University of Western Australia, and the National Science Foundation (USA) ANT-1043749. KKSL was supported by a University Postgraduate Award for International Students (UPAIS) and an RTP International Fees Offset scholarship (RTPFI) administered by The University of Western Australia, as well as a postgraduate doctoral scholarship from the Natural Sciences and Engineering Research Council of Canada (NSERC). These funding bodies did not have a role in the design of the study, the collection, analysis, and interpretation of data, or in writing the manuscript. Availability of data and materials The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request and GenBank accessions appear in the manuscript.Peer reviewedPublisher PD

Spaghetti to a Tree:A Robust Phylogeny for Terebelliformia (Annelida) Based on Transcriptomes, Molecular and Morphological Data

Terebelliformia&mdash;&ldquo;spaghetti worms&rdquo; and their allies&mdash;are speciose and ubiquitous marine annelids but our understanding of how their morphological and ecological diversity evolved is hampered by an uncertain delineation of lineages and their phylogenetic relationships. Here, we analyzed transcriptomes of 20 terebelliforms and an outgroup to build a robust phylogeny of the main lineages grounded on 12,674 orthologous genes. We then supplemented this backbone phylogeny with a denser sampling of 121 species using five genes and 90 morphological characters to elucidate fine-scale relationships. The monophyly of six major taxa was supported: Pectinariidae, Ampharetinae, Alvinellidae, Trichobranchidae, Terebellidae and Melinninae. The latter, traditionally a subfamily of Ampharetidae, was unexpectedly the sister to Terebellidae, and hence becomes Melinnidae, and Ampharetinae becomes Ampharetidae. We found no support for the recently proposed separation of Telothelepodidae, Polycirridae and Thelepodidae from Terebellidae. Telothelepodidae was nested within Thelepodinae and is accordingly made its junior synonym. Terebellidae contained the subfamily-ranked taxa Terebellinae and Thelepodinae. The placement of the simplified Polycirridae within Terebellinae differed from previous hypotheses, warranting the division of Terebellinae into Lanicini, Procleini, Terebellini and Polycirrini. Ampharetidae (excluding Melinnidae) were well-supported as the sister group to Alvinellidae and we recognize three clades: Ampharetinae, Amaginae and Amphicteinae. Our analysis found several paraphyletic genera and undescribed species. Morphological transformations on the phylogeny supported the hypothesis of an ancestor that possessed both branchiae and chaetae, which is at odds with proposals of a &ldquo;naked&rdquo; ancestor. Our study demonstrates how a robust backbone phylogeny can be combined with dense taxon coverage and morphological traits to give insights into the evolutionary history and transformation of traits

Description and Relationships of Chaetopterus pugaporcinus, an Unusual Pelagic Polychaete (Annelida, Chaetopteridae)

An extraordinary new species, Chaetopterus pugaporcinus, is described from eight specimens collected from deep mesopelagic waters off Monterey Bay, California, by remotely operated vehicles. All specimens exhibit a consistent combination of both adult and larval characteristics, leaving in question the maturity of the specimens. All specimens lack ciliated larval bands and the stout, modified chaetae (cutting spines) typically found in segment A4 of chaetopterids. If the specimens described here are larvae, they are remarkable for their size, which ranged from 10 to 21 mm total length, nearly twice the length of the largest polychaete larvae previously reported and 5 to 10 times larger than known chaetopterid larvae. Then too, their lack of segment addition prior to settlement would be atypical. If adult, they are particularly unusual in their habitat choice and body form. Morphology of the uncini and comparison to larval morphology indicated a close relationship to either Chaetopterus or Mesochaetopterus. However, the lack of cutting spines and typical adult morphology made it impossible to determine to what genus this species should be allied. Thus, we carried out the first molecular phylogenetic analysis of the Chaetopteridae in order to appropriately place and name the new species. Three partial genes were sequenced for 21 annelid species. The sequencing also provides the first molecular evidence that Chaetopterus variopedatus sensu Hartman (1959) is not a single cosmopolitan species. The question of C. pugaporcinus being a delayed larva or a genuine holopelagic chaetopterid is discussed

Using a Combined Approach to Explain the Morphological and Ecological Diversity in Phanogenia gracilis Harlaub, 1893 (Echinodermata: Crinoidea) sensu lato: Two Species or Intraspecific Variation?

Phanogenia gracilis sensu lato is a shallow-water crinoid distributed throughout the Indo-western Pacific. The taxonomy of P. gracilis s.l. is clouded by the presence of two distinct morphotypes, each differing in morphology and ecology. The goal was to determine the taxonomic status of P. gracilis s.l. using partial gene sequences of two mitochondrial DNA genes, cytochrome oxidase c subunit I and NADH dehydrogenase subunit II, in conjunction with morphological and ecological data. The molecular phylogenies revealed three lineages separated by 5.0–6.6% corrected genetic distance, which is consistent with the genetic distances among other echinoderm species. Neither morphotype was monophyletic, nor was any examined morphological character exclusive to any one lineage. Discriminant function analysis (DFA) of the morphological and ecological data yielded significant results when grouping P. gracilis by morphotype and by clades recovered in the phylogenetic analyses, but grouping by sample locality was rejected. Although DFA results of grouping by clade were significant, jackknife support was weak, while only correctly grouping specimens by their respective clades 65% of the time. The results suggest the possibility of cryptic species, but additional molecular and morphological data are needed to confirm this. This study demonstrates the need to reevaluate the taxonomy of crinoid species and their respective diagnostic characters

Two new meiofaunal species of Trilobodrilus (Dinophilidae, Annelida) from California, USA

We describe two new species of the annelid genus Trilobodrilus Remane, 1925 (Dinophilidae Verill, 1892) from an intertidal and a subtidal location in San Diego, California. These two species show morphological and molecular divergences between each other and the previously described, geographically distant species. Intertidal T. windansea sp. nov. differs from subtidal T. ellenscrippsae sp. nov. most remarkably in the number and pattern of ciliary tufts and bands on the prostomium and along the body length, besides showing ca 15% difference in gene fragments of COI and CytB. Trilobodrilus windansea sp. nov., though nesting with T. ellenscrippsae sp. nov. in the molecular phylogenetic analyses, morphologically resembles the Japanese T. itoi Kajihara, Ikoma, Yamasaki & Hiruta, 2015 most closely, but still differs from this species in the higher number of apical ciliary tufts, an additional ciliary row posterior to the second ciliary band, and by lacking a forth ciliary band and segmentally arranged lateral ciliary tufts. Trilobodrilus ellenscrippsae sp. nov. is morphologically most similar to the Japanese T. nipponicus Uchida & Okuda, 1943, but is much shorter, has more apical ciliary tufts, and less regularly arranged lateral ciliary tufts along the body. All species differ significantly in all compared gene fragments, and no obvious correlation was found between habitat and the species morphology or relationships