New Taxa and Occurrences of Mesophotic and Deep-sea Goniasteridae (Valvatida, Asteroidea) from Okinawa and adjacent regions.

Thirteen new records of Goniasteridae showing mesophotic occurrence are presented, including a new species of Pseudoceramaster doto n. sp. from southern Japan and a new genus and species, Churaumiastra hoshi nov. gen. nov. sp. which occurs in southern Japan, the Philippines and Western Australia.

Two new species of the bathyal holothurian genus Pannychia (Elasipodida, Laetmogonidae) from Japanese waters.

Sea cucumbers are one of the most common large animals in the deep-sea benthic communities, and those of the genus Pannychia are particularly abundant in the bathyal North Pacific Ocean. In Japanese waters, three species of Pannychia have been reported, mainly from the northern and eastern parts of the country. Here, we describe two new species from the western part of Japan. These two new species were placed in Pannychia by the presence of dorsal papillae on the ventrolateral radii and the presence of large wheel ossicles with rim teeth. They are distinguished from all other nominal species of Pannychia on the basis of the morphological characteristics of their body wheel ossicles. Pannychia nagasakimaruae sp. nov. has a unique ossicle composition in its dorsal and ventral body walls: four forms of wheel ossicles. Pannychia rinkaimaruae sp. nov. differs from other congeners in its small wheel ossicles in the dorsal and ventral body walls, which have conical rim teeth. We barcoded partial COI gene sequences from holotypes and paratypes of two new Japanese species. Our molecular phylogenetic analysis showed that these two new morphologically recognized Japanese species form distinct clades separated from other Pacific Pannychia species, so that the two new Japanese species were also supported by genetic results. In addition, we describe and visualize the poorly calcified calcareous rings of the two new species using X-ray µCT system, a useful method for observing such structures, which are important structures in holothurian anatomy.

Complete mitochondrial genome of a sea cucumber, Euapta godeffroyi (Echinodermata, Holothuroidea, Apodida, Synaptidae).

We determined the complete mitochondrial genome sequence of a holothurian Euapta godeffroyi belonging to the order Apodida. The complete mitogenome of E. godeffroyi was 16,410 bp in length and consisted of 13 protein-coding genes (PCGs), two ribosomal RNA genes, and 22 transfer RNA genes. The orders of PCGs and rRNAs did not match those of any recorded holothurian mitogenomes. The maximum likelihood (ML) phylogenetic tree placed E. godeffroyi as the sister group to chiridotid species and supported the monophyly of the order Apodida.

Complete mitochondrial genome of the Pacific limpet Cellana nigrolineata (Gastropoda: Patellogastropoda) determined by shotgun sequencing using the Illumina NGS platform.

The Pacific limpet Cellana nigrolineata is one of the most commonly found limpets in the intertidal shores of Japan. Here, we report the full mitogenome sequence of an individual specimen of the species, which was collected from the intertidal rocky beach in the Nada beach of Gobo City, Wakayama, Japan (33.8316 N, 135.1751 E), in 2018. The sequence was determined by the shotgun sequencing method using the NGS Illumina MiSeq platform. The genomic structure of C. nigrolineata is the same as the previously reported congener, C. radiata, which shows a representative Nacellidae and metazoan mitogenomic structures. The mitogenome has all of its 37 genes included in its 16,153 bp, with one control region located between the tRNA-Cys and tRNA-Gly genes. In order to clarify the phylogenetic position of C. nigrolineata in Gastropoda, a data set including the mitogenomes of 10 patellogastropods, 10 non-patellogastropod gastropods, and four outgroups were used in maximum likelihood inferences. Although with some exceptions, the resulting phylogeny supported the monophylies of traditionally accepted gastropod subclasses, and thus confirms the position of C. nigrolineata in Patellogastropoda.

The first complete mitochondrial genome of the Northern Pacific deep-sea goniasterid sea star Ceramaster japonicus (Sladen, 1889) determined using NGS-based shotgun sequencing.

The full mitogenome of an ethanol-preserved museum specimen of Ceramaster japonicus was determined using the NGS Illumina MiSeq platform. The specimen was collected from Tosa Bay, Japan, facing the Pacific Ocean (33.0781 N 134.0601 E), at 700 m depth in 2011. The mitogenome shows a typical metazoan genomic structure, with all of the 37 genes included in its 16,370 base-long mitogenome. We conducted phylogenetic analyses using a data set including 18 publicly available asteroids rooted against five ophiuroids as outgroups. The result confirms the position of C. japonicus in the order Valvatida. The complete mitogenome of C. japonicus reported here is the first reported for the family Goniasteridae Forbes, 1841.

Two new deep-sea species of the genus Henricia (Asteroidea: Spinulosida: Echinasteridae) from Japanese waters.

Two new deep-sea Henricia species, Henricia margarethae n. sp. and Henricia fragilis n. sp. are described from Sagami Bay and the Ogasawara Islands in Japan. The two new species show an affinity with eight congeners in having multiple furrow spines and abactinal papular areas which are larger than surrounding plates. The two species described herein are characterized by the arrangement of abactinal pseudopaxillae, the arrangement of abactinal papulae, the shape and arrangement of abactinal spines, the length of intermarginal and ventrolateral series, and the armament of superomarginal, inferomarginal, and adambulacral plates.

A New Species of the Genus Ophiomonas Djakonov (Echinodermata: Ophiuroidea: Amphilepididae) from the Deep-Sea of Japan.

A new species, Ophiomonas shinseimaruae, is described based on five specimens collected from deep water settings, southeast of Cape Erimo, Hokkaido, Japan. Ophiomonas shinseimaruae sp. n. is distinguished from other congeners based on the following characters: elongate semi-circular and separated radial shields; triangular oral shields; flat and broad tentacle scales on the second tentacle pore; octagonal dorsal arm plates, approximately three times wider than long on proximal portion of the arm; and three arm spines present proximally on the arm. This is the first record of the genus Ophiomonas from Japanese waters. The COI nucleotide sequence for Ophiomonas shinseimaruae sp. n. is provided.

A taxonomic review of the genus Astrocladus (Echinodermata, Ophiuroidea, Euryalida, Gorgonocephalidae) from Japanese coastal waters.

Japanese species of the genus Astrocladus (Echinodermata, Ophiuroidea, Euryalida, Gorgonocephalidae) are reviewed. Astrocladus coniferus recently has two junior synonyms, A. dofleini Döderlein and A. pardalis Döderlein, however, status of these species has long been questioned. These species concepts have not been reviewed in recent years and no molecular phylogenetic analyses have been performed. Observations of the lectotype of A. coniferus, as well as the lectotype and four paralectotypes of A. dofleini and the holotype of A. pardalis have revealed that A. coniferus and A. pardalis are conspecific and morphologically distinguishable from A. dofleini. Astrocladus coniferus and A. dofleini are supported as distinct species by our molecular data. Additionally, we re-describe A. exiguus and A. annulatus, based on recently collected specimens and the holotype. We conclude that four species, A. annulatus, A. coniferus, A. dofleini, and A. exiguus are present in Japanese waters.

Two new species of the genus Chironephthya (Octocorallia, Alcyonacea, Nidaliidae, Siphonogorgiinae) from the Gulf of Thailand.

Two new species of the genus Chironephthya, C. sirindhornae sp. nov. and C. cornigera sp. nov., are described based on three specimens collected from the Gulf of Thailand. Both species are well distinguished from the previously described species of the genus Chironephthya by their colonies consisting of multiple stems that stand upright from a common base, and by a significantly thinner canal wall without large spindles. As a result of phylogenetic analyses using COI, mtMutS, and 28S rDNA sequences of these two species, these three specimens constituted an independent small clade within a large mixed clade of Siphonogorgia and Chironephthya, with the two species slightly different from each other. The discrepancy in the morphology suggested the erection of a new genus to accommodate these species, however, as the subclade was included in a large mixed clade of Siphonogorgia and Chironephthya, we place these species within genus Chironephthya. Our results further highlight the continuing confusion between Siphonogorgia and Chironephthya, and demonstrate the need for taxonomic revision of these genera.

New species and occurrence records of Japanese Solasteridae and Ganeriidae including a new species of Paralophaster from the North Pacific with an overview of Hyalinothrix.

Japanese waters contain a highly diverse echinoderm fauna including many undiscovered species, especially in deeper-water settings. Molecular phylogenetic data has shown a close relationship between three established families of asteroids, the Asterinidae, the Solasteridae and the Ganeriidae, which are three groups that are well-represented in the region. We present two undescribed species of solasterids, Lophaster cactorum n. sp. and Paralophaster gomo n. sp., the latter represents a genus which had previously been known primarily from Antarctic settings. New occurrence records of the tropical deep-sea Pacific solasterid Rhipidaster vannipes Sladen, 1889 has led to synonymy of Xenorias polyctenius Fisher, 1913. Three undescribed species of Hyalinothrix, Hyalinothrix diversus n. sp., Hyaliothrix enoki n. sp. and Hyalinothrix virtrispinum n. sp. are described. Nepanthia grangei McKnight, 2001 is transferred to Hyalinothrix. A new subfamily, the Hyalinothricinae is established within the Asterinidae, including Tarachaster and Seriaster, which was formerly assigned to the Solasteridae. Knightaster is reassigned to the Asterinidae from the Ganeriidae.

Redescription of Synactinernus flavus for the First Time after a Century and Description of Synactinernus churaumi sp. nov. (Cnidaria: Anthozoa: Actiniaria).

Two species of Synactinernus sea anemones were found in Japanese waters. Synactinernus flavus Carlgren, 1918, the only described species of this genus, is rediscovered from off the Goto Islands a century after the original description. Synactinernus flavus was once synonymized with Isactinernus quadrilobatus Carlgren, 1918; however, we show that, based on morphological (including examination of type specimens) and molecular (using nuclear 18S rDNA) evidence, these species are completely different. The other species, Synactinernus churaumi sp. nov., was found off Ishigaki Island and Okinawa Island by a remotely operated vehicle (ROV), and had been kept for 15 years in a tank at the Okinawa Churaumi Aquarium. There are clear differences between these two species; therefore, we describe the second species and revise the diagnosis of Synactinernus.

Two species of Edwardsia having gigantic nematocysts, E. aff. tuberculata br />and E. alternobomen sp. nov. (Cnidaria; Anthozoa; Actiniaria; Edwardsiidae) from Japan.

The genus Edwardsia de Quatrefages, 1842 is the group of worm-like sea anemones of the family Edwardsiidae, characterized by having nemathybomes on their body wall and physa at their aboral end. This genus accommodates a lot of species, but only three have been known from Japanese waters. In this study, we report Edwardsia aff. tuberculata Duben and Koren, 1847 and describe a new species E. alternobomen sp. nov. from seas around Japan. Both are characterized by prominent, papillae-like nemathybomes which contain unusually large nematocysts. Some nematocysts of E. alternobomen sp. nov. are over 200 µm in length, which are the largest reported for a member of Edwardsiidae.

First record of Hamacantha (Porifera, Demospongiae, Merliida, Hamacanthidae) from Japan, with description of two new species.

Two new species of thinly encrusting sponge Hamacantha (Demospongiae, Merliida, Hamacanthidae) are described from Japan. Hamacantha (Vomerula) mamoi sp. nov. was collected from Sagami Bay, and Hamacantha (Vomerula) umisachii sp. nov. from off Hachijo Island. This is the first record of Hamacantha and the Hamacanthidae from Japan. H. (V.) mamoi sp. nov. is characterized by having styles, two types of diancistras and one of sigmas. Only two known species have the same spicule composition: H. (V.) acerata Lévi, 1993 and H. (V.) esperioides Ridley Dendy, 1886, described from New Caledonia, and south-west Africa and south-east South America, respectively. H. (V.) acerata has larger diancistras and much smaller sigmas compared with those of H. (V.) mamoi sp. nov. H. (V.) esperioides can be separated by having larger styles and smaller sigmas than those of H. (V.) mamoi sp. nov. H. (V.) umisachii sp. nov is characterized by having styles, diancistras, cyrtancistra-like diancistras and sigmas. Hamacantha (V.) carteri Topsent, 1904 seems to have similar spicule composition, however the size of all spicule types is different.

A new species of Fibularia from Japanese waters with a redescription of F. japonica and F. ovulum (Echinodermata: Echinoidea: Clypeasteroida).

A new species, Fibularia coffea sp. nov., occurs from shallow waters in Japan. This new species is distinguished from the other species of Fibularia by the following characters: test height is low, oral surface is slightly depressed toward the peristome, number of pores of petal III continues to increase with the test growth, reaching over 30 at TL > 7.5 mm, and black pigments form symmetric pentaradial on aboral surface in living animals. Two further Japanese species, Fibularia japonica and F. ovulum, are redescribed based on the type specimens (F. japonica) and additional specimens (F. ovulum), respectively. A tabular key to the extant species of Fibularia is also provided. A partial fragment of the mitochondrial gene cytochrome oxidase subunit I (COI) of the type specimens of F. coffea sp. nov. and the additional specimen of F. japonica was sequenced for barcoding in future works.

Description of three new species of Scolanthus (Cnidaria, Anthozoa, Actiniaria, Edwardsiidae): first records of the genus from Japan.

Scolanthus is one genus of Edwardsiidae, a speciose family of burrowing worm-like sea anemones characterized by lacking a physa-like aboral end and by possessing nemathybomes on the whole body except at the distal end. This genus has been recorded worldwide, but there have been no specimens collected from Japan. In this study, we discovered four Scolanthus species in Japan for the first time: Scolanthusarmatus (Carlgren, 1931) and Scolanthuskopepe sp. n. from the Ogasawara Islands, Scolanthusena sp. n. from Ena Bay, Kanagawa, and Scolanthusisei sp. n. from Sugashima Island, Mie.

A taxonomic review of the genus Astrodendrum (Echinodermata, Ophiuroidea, Euryalida, Gorgonocephalidae) with description of a new species from Japan.

A revision of the genus Astrodendrum Döderlein (Ophiuroidea, Euryalida, Gorgonocephalidae) is based on 14 specimens, including the holotypes of Astrodendrum galapagense A. H. Clark and Astroconus capense Mortensen and a syntype of Gorgonocephalus sagaminus Döderlein. A new species Astrodendrum spinulosum is described from the Pacific coast of Japan. It is distinguished from its congeners in having conical external ossicles on aboral side of the disc; bulges on lateral edges of proximal arms; 1 terminal projection on each arm spine of proximal portion of the arm; 2 or 3 secondary teeth on each hook-shaped arm spine of distal portion of the arm. A taxonomic key to all six species of the genus Astrodendrum is provided.

Description of a New Subfamily, Astrocloninae (Ophiuroidea: Euryalida: Gorgonocephalidae), Based on Molecular Phylogeny and Morphological Observations.

Previous phylogenetic studies of the family Gorgonocephalidae (brittle stars and basket stars) have identified three subfamilies, Astrotominae, Astrothamninae, and Gorgonocephalinae. The genus Astroclon was tentatively assigned to the subfamily Astrothamninae in previous studies, but its morphology is enigmatic and molecular data of the genus was insufficient. Therefore, the systematic position of Astroclon required confirmation to reconstruct the accurate systematics of the Euryalida. In the present study, we sought to clarify the subfamilial classification in the family Gorgonocephalidae (Echinodermata: Ophiuroidea: Euryalida). We revisited molecular phylogenetics of the Gorgonocephalidae including Astroclon and the major taxa in the family. The molecular analysis supported monophyly of the two species of Astroclon and its clear separation from Astrothamninae. The two Astroclon species were also distinguished from the other two subfamilies, Astrotominae and Gorgonocephalinae. Astroclon and three other subfamilies were divided in the basal position of the Gorgonocephalidae, and were assigned to subfamilies. A new subfamily, Astrocloninae was monotypically established for Astroclon in addition to the previous three subfamilies. Morphology of the first ventral arm plates and tentacle pores also supported distinctiveness of the new subfamily.

A taxonomic revision of the genus Apostichopus (Holothuroidea: Stichopodidae) from Japan.

Complete redescriptions of sea cucumbers in the genus Apostichopus Liao, 1980 are provided using the type specimens and specimens deposited in the National Museum of Nature and Science, Tsukuba, Japan. The genus consists of A. armatus (Selenka, 1867) and A. japonicus (Selenka, 1867), which can be distinguished by some spicules in the dorsal body wall; the rim of reduced table spicules in A. armatus is spinous, while that in A. japonicus is smooth. Spicules from the tentacles, papillae, tube feet, and cloaca are similar for both species.

Non-destructive morphological observations of the fleshy brittle star, Asteronyx loveni using micro-computed tomography (Echinodermata, Ophiuroidea, Euryalida).

The first morphological observation of a euryalid brittle star, Asteronyx loveni, using non-destructive X-ray micro-computed tomography (µCT) was performed. The body of euryalids is covered by thick skin, and it is very difficult to observe the ossicles without dissolving the skin. Computed tomography with micrometer resolution (approximately 4.5-15.4 µm) was used to construct 3D images of skeletal ossicles and soft tissues in the ophiuroid's body. Shape and positional arrangement of taxonomically important ossicles were clearly observed without any damage to the body. Detailed pathways inside the vertebral ossicles, lateral arm plates, and arm spines for passage of nerves and water vascular structures were observed. Inter-vertebral muscles were also observed. Forms and 3D arrangements of many important taxonomical characters of the euryalids were scrutinized by µCT in high enough resolution for taxonomic description of ophiuroids.

The 'Antenna Balloon Anemone' Found in the Seto Inland Sea: New Genus and Species of Sea Anemone, Antennapeachia setouchi (Cnidaria, Actinaria, Haloclavidae).

In the present study, we report the identification of a sea anemone, Antennapeachia setouchi, collected in the Seto Inland Sea, which represents a new genus and new species. This new species has unusual tentacle and mesenterial arrangements that have not been observed in other species of Haloclavidae. There are 12 regular marginal tentacles and two 'antenna tentacles,' with the latter always rising upward and located on the oral disk near the mouth; the species is also characterized by its peculiar mesenterial pairs, consisting of a macrocneme and a microcneme. Furthermore, this species shows an interesting behavior: it can inflate its body like a balloon, lift above the seafloor, and drift with the sea current. The presence of a single, strong siphonoglyph, physa-like aboral end, and the lack of sphincter muscle classify this sea anemone within Haloclavidae. It resembles Peachia species, but cannot be classified in this genus as the new species has two pairs of mesenteries, consisting of a macrocneme and a microcneme, and irregular antenna tentacles. Therefore, we propose a new genus Antennapeachia to accommodate this species.