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Gastropods of the genus Mucronalia (Eulimidae) are known ectoparasites of brittle stars (Ophiuroidea). However, the identities of host species are only known for three of some ten described species in the genus. Here, we report associations of Mucronalia snails, including one new species, with ophiuroid hosts from Japan and New Caledonia: M. spp. aff. alba with Ophiomastix annulosa, Ophiomastix mixta, and Ophiocoma cynthiae; M. sp. cf. exquisita with Amphioplus (Amphioplus) sp.; Mucronalia ryukyuensis n. sp. with Ophionereis porrecta; and Mucronalia sp. with Amphiura velox. Mucronalia ryukyuensis n. sp. is described from Okinawa, southwestern Japan. The new species is characterized by its slender shell with a large body whorl and aperture compared with other species of the genus. Among Japanese congeners, the shell of the new species is most similar to that of M. exilis, but differs in having a teleoconch with less-convex whorls, regularly increasing in diameter. The present study corroborates Warén's (1983) general rule that eulimids in a single genus parasitize hosts of the same echinoderm class, and our records suggest that closely related species of Mucronalia tend to exploit hosts of a more restricted lineage. We also briefly discuss the divergence processes of Mucronalia snails, which likely involve host shifts and geographic isolation. [ABSTRACT FROM AUTHOR]

Echinoderms, including sea urchins and starfish, have played important roles in cell, developmental and evolutionary biology research for more than a century. However, since most of them take a long time to mature sexually and their breeding seasons are limited, it has been difficult to obtain subsequent generations in the laboratory, resulting in them not being recognized as model organisms in recent genetics research. To overcome this issue, we maintained and obtained gametes from several nonmodel sea urchins in Japan and finally identified Temnopleurus reevesii as a suitable model for sea urchin genetics. Genomic and transcriptomic information was obtained for this model, and the DNA database TrBase was made publicly available. In this review, we describe how we found this species useful for biological research and show an example of CRISPR/Cas9 based knockout sea urchin. [ABSTRACT FROM AUTHOR]

The starfish Asterias amurensis is a marine pest native to the northwestern Pacific and has successfully invaded southern Australia. Asterias amurensis have caused substantial environmental and economic impacts in both native and non-native regions. However, little information is available about the genetic features of its native populations, especially for those in North China. Here we sequenced the complete mitochondrial genomes of five individuals from different locations in China and compared their characteristics with three mitogenomes available from Japan. Multiple analyses and comparisons revealed little difference in the gene composition, gene order, codon usage, and nucleotide content among the eight mitogenomes. However, intraspecific phylogenetic reconstruction unveiled two divergent lineages between specimens from North China plus Ushimado (Seto Inland Sea, Japan) and northern Japan (Asamushi and Onagawa). This conclusion was backed by an analysis of pairwise genetic distances, which showed that individuals from different lineages had relatively higher values (all above 2%). Based on knowledge of paleoenvironmental and tectonic activity in the northwestern Pacific, the two lineages might have originated during the Early Pliocene due to the isolation of the East China Sea from the Japan Sea/East Sea during that time, while the present-day distribution of these lineages have likely been influenced by the ocean current system. [ABSTRACT FROM AUTHOR]

More than 100 individuals of sea cucumber larvae were collected in the Japanese coastal sea of Moroiso, Sagami Bay, Kanagawa Prefecture, central-eastern Japan, in January 2018. Based on an obtained sequence of mitochondrial 16S rRNA gene region of one juvenile, it was identified as Sclerodactyla multipes by BLAST search with 0.3% genetic distance. The developmental process of the S. multipes was observed for three months, in which time, they grew from 250 μm to about 4 mm in length; here they showed distinct tentacles and dermal ossicles. Detailed morphological features of this species were described based on stereomicroscopic, fluorescence and SEM observations for the first time. This is the first description of life history through planktonic larva to juveniles in the family Sclerodactylidae. [ABSTRACT FROM AUTHOR]

A new parasitic species of eulimid gastropod, Haliella seisuimaruae sp. nov., is described from bathyal (728-978 m) waters off the Pacific coasts of Japan. It shows the closest resemblance to the type species H. stenostoma from the North Atlantic and Barents Sea in having a tall shell with an almost straight outer lip, but differs in having a junction of the parietal wall and columellar lip at 38% of the aperture height from the suture (33% in H. stenostoma), a slightly wider aperture and a more curved and extended columellar lip. The holotype of H. seisuimaruae sp. nov. was found attached to an irregular sea urchin, Brissopsis sp. cf. luzonica (Spatangoida: Brissidae). This represents the first direct observation of parasitic ecology and echinoderm host for the genus Haliella. A new replacement name, Eulima tsushimensis nom. nov., is proposed here for Eulima stenostoma A. Adams, 1861, which is preoccupied by Eulima stenostoma Jeffreys, 1858 (type of Haliella). [ABSTRACT FROM AUTHOR]

Three new species of the ascothoracidan crustacean genus Dendrogaster Knipovich, 1890 (Dendrogasteridae) are described from goniasterid sea-stars in Japan. Dendrogaster komatsuae sp. nov. and D. tobasuii sp. nov. were found respectively in the coelomic cavities of Lithosoma japonica Hayashi, 1952 and two species of Mediaster: M. arcuatus (Sladen, 1889) and M. brachiatus Goto, 1914 from the Kumano-nada Sea. Dendrogaster nagasakimaruae sp. nov. was similarly found in Nymphaster euryplax Fisher, 1913 from the East China Sea. Partial DNA sequences of the cytochrome c oxidase subunit I and 16S ribosomal RNA genes were determined for D. tobasuii sp. nov. These findings represent the first records of Dendrogaster from the host family Goniasteridae in Japan. [ABSTRACT FROM AUTHOR]

In 2011, a tropical holothurian was found off the temperate coast of Kagoshima, Kyushu, Japan. This holothurian was identified as Stichopus naso Semper, 1867, which was first described in the Philippines, and is known to be distributed within the tropical Indo-West Pacific region. Herein, we examined its morphological characteristics and compared it with pre-described examples and discuss its origin from the perspective of climate change and artificial transfer. We considered that both perspectives are plausible because sea water temperature has recently risen around Japan, creating the possibility of eggs and larval transfer from southern regions and the consequent establishment of adult S. naso populations. Accidental introduction via ballast water from vessels and other pathways may not be implausible. In any case, ocean warming caused by global climate change is considered as a key factor in the survival and settlement of adult S. naso populations. [ABSTRACT FROM AUTHOR]

Two new species and two new occurrence records of the genus Ophiambix Lyman, 1880 (Echinodermata: Ophiuroidea), were found on hydrothermal vents at the Pacific coast of Japan. Ophiambix kagutsuchi, new species, is distinguished from other congeners in having small granules separated from each other on aboral surface of disc, flat teeth, second from oral-most arm spines being cylindrical and spiniform in shape, and one small and spiniform tentacle scale on each tentacle pore. Ophiambix macrodonta, new species, is distinguished from the other congeners in having small granules circularly arranged surrounding the periphery of disc scales on aboral surface of disc, flat teeth, second from oral-most arm spines being flat and leaf-like in shape, and one small and spiniform tentacle scale on each tentacle pore. Furthermore, Ophiambix epicopus Paterson & Baker, 1988, was recorded from Japan for the first time and another congener, Ophiambix aculeatus Lyman, 1880, was also collected. Ophiambix kagutsuchi, new species, and Ophiambix macrodonta, new species, were collected from deep-sea chemosynthetic environments. A tabular key to all six species of the genus Ophiambix is provided. [ABSTRACT FROM AUTHOR]

The subgenus Setihenricia Chichvarkhin and Chichvarkhina, 2017 currently consists of 32 out of 94 species of sea stars in the genus Henricia Gray, 1840. However, only 10 have been molecularly ascertained as to the phylogenetic position. Based on seven mitochondrial gene markers (16S rRNA, COI, tRNA-Ala, tRNA-Leu, tRNA-Asn, tRNA-Gln, and tRNA-Pro), we performed molecular analyses to assess the monophyly of Setihenricia using 16 species of Henricia from Japanese waters, as well as other congeners for which sequences were available in public databases. The monophyletic Setihenricia was only weakly recovered because the support values were low, but we assume this taxon may be valid in consideration of a morphological key. Henricia kinkasana Hayashi, 1940 is herein identified as a new member of Setihenricia, based on molecular and morphological evidence. Sequences in the public databases previously identified as H. compacta (Sladen, 1889) and H. obesa (Sladen, 1889) were nested in the Setihenricia clade; these two species are also likely members of Setihenricia . Our morphological assessment yielded three findings: (1) the number of the rows of spines on each inferomarginal plate, being three or more, appears to be a useful diagnostic character for Setihenricia, as has been suggested in previous studies, (2) the degree of spine tapering turned out to be less relevant in diagnosing the subgenus than previously supposed, (3) two newly introduced characters--( i ) the width of adambulacral plates and ( ii ) the ratio of two measurements in ambulacral plates to the length of interradius--may be effective to distinguish members of this apparent Henricia subclade from other members of the genus. [ABSTRACT FROM AUTHOR]

A new dendrochirotid sea cucumber collected in the intertidal zone of western Japan, Lipotrapeza littoralis sp. nov., is described. This species has a medium body size (approximately 30-80 mm), brownish body color, 20 tentacles arranged in a double circle (15+5), a long calcareous ring, ten anal papillae and five anal scales, and numerous pedicels covering the entire body at an even density. For comparison, we also examined the syntype specimens of Lipotrapeza japonica Heding and Panning, 1954 and provide illustrations of the general appearance of its body, calcareous ring, and ossicles. The calcareous rings of both species are very similar in appearance, but the new species is readily distinguishable from L. japonica by the number of anal papillae. The appearance of the rosette ossicles also differs in the two species. [ABSTRACT FROM AUTHOR]

Well preserved, articulated brittle star skeletons from the early Carnian (early Late Triassic)HalobiaShales of Yamaguchi, Japan, are described as a new genus and species of the family Ophiacanthidae:Leadagmara gracilispina. The new form constitutes the oldest unequivocal representative of this extant ophiuroid family, significantly extending its stratigraphical range. The first cladistic analysis of the Ophiacanthidae including all extant genera suggestsL. gracilispinaholds a basal, but not the basalmost, position within the family, forming a sister group with the extantOphiomedeaandOphioprististo the other ophiacanthids except forOphiologimus, which itself is sister to all other ophiacanthids. These results imply that ophiacanthids originated in the pre-Carnian. A critical re-evaluation of the ophiacanthid fossil record reveals that the vast majority of records consist of dissociated lateral arm plates, which provide no insights into divergence times of the lineages. Among the few records of articulated specimens, onlyInexpectacantha acrobaticafrom the Pliensbachian of France proved sufficiently well-known to yield phylogenetically relevant information. Its position within the ophiacanthid clade indicates that more than half of the extant ophiacanthid lineages, in particular the former ophiacanthinids and ophiotominids, must have diverged by the Pliensbachian. http://zoobank.org/urn:lsid:zoobank.org:pub:F64E44C3-7275-4EC8-B048-4C7B2C6D57EF [ABSTRACT FROM AUTHOR]

Reproduction and larval/post-larval development of the one of the smallest known comatulid Dorometra sesokonis were studied on the coral reefs of Sesoko-jima Island, Okinawa, Japan. Breeding individuals were found every month from May 2003 to April 2004 indicating continuous reproduction. Individuals possessed both mature ovaries and testes, and were therefore characterized as simultaneous hermaphrodites. This species was observed to be an external brooder in which the embryos developed on the surface of parental genital pinnules until the doliolaria larval stage, and subsequently released doliolariae settled on substrata within 4 days after hatching. Larvae then metamorphosed into the post-larval cystidean stage, which lasted for more than a month. The reproductive features of this species are unique among crinoids, and, together with juvenile morphological features observed in adults, can be interpreted as adaptations to their cryptic habitat, which is subject to frequent natural disturbances. [ABSTRACT FROM AUTHOR]

The specimens of Paralepas maculata on a sea urchin, Prionocidaris sp. were collected in Okinawa, southern Japan. This species has not been reported since its original description. This represents the first observation of this species from Okinawa and the first instance found on this sea urchin species. In this paper, the morphology of the new P. maculata specimens is reported, and compared with the type series of this species. Small individuals were found on the holotype. The probable androdioecious sexual system of the species, which includes dwarf-male like individuals and hermaphrodites, is discussed. This study was facilitated by the collaboration of scientists and aquarium staff, suggesting the potential of such collaborations in biodiversity studies. [ABSTRACT FROM AUTHOR]