A taxonomic review of the genus Asterostegus (Echinodermata: Ophiuroidea) : with the description of a new species

A revision of the genus Asterostegus Mortensen, 1933 (Echinodermata: Ophiuroidea: Euryalidae) is based on seven specimens, including the holotype of Asterostegus maini McKnight, 2003. A new species, Asterostegus sabineae sp. nov., is described from off Reunion Island and two other species, A. tuberculatus Mortensen, 1933 and A. maini, are redescribed. A tabular key to the three species of the genus Asterostegus is provided. Some terminology of the taxonomy of euryalid ophiuroids is revised

Development of two new sets of PCR primers for eDNA metabarcoding of brittle stars (Echinodermata, Ophiuroidea)

汲んだ水から深海生物の種類を判別 --世界初「クモヒトデメタバーコーティング」技術を開発--. 京都大学プレスリリース.Brittle stars (class Ophiuroidea) are marine invertebrates comprising approximately 2, 100 extant species, and are considered to constitute the most diverse taxon of the phylum Echinodermata. As a non-invasive method for monitoring biodiversity, we developed two new sets of PCR primers for metabarcoding environmental DNA (eDNA) from brittle stars. The new primer sets were designed to amplify 2 short regions of the mitochondrial 16S rRNA gene, comprising a conserved region (111–115 bp, 112 bp on average; named “16SOph1”) and a hyper-variable region (180–195 bp, 185 bp on average; named “16SOph2”) displaying interspecific variation. The performance of the primers was tested using eDNA obtained from two sources: a) rearing water of an 2.5 or 170 L aquarium tanks containing 15 brittle star species and b) from natural seawater collected around Misaki, the Pacific coast of central Japan, at depths ranging from shallow (2 m) to deep (> 200 m) sea. To build a reference library, we obtained 16S rRNA sequences of brittle star specimens collected from around Misaki and from similar depths in Japan, and sequences registered in International Nucleotide Sequence Database Collaboration. As a result of comparison of the obtained eDNA sequences with the reference library 37 (including cryptic species) and 26 brittle star species were detected with certain identities by 16SOph1 and 16SOph2 analyses, respectively. In shallow water, the number of species and reads other than the brittle stars detected with 16SOph1 was less than 10% of the total number. On the other hand, the number of brittle star species and reads detected with 16SOph2 was less than half of the total number, and the number of detected non-brittle star metazoan species ranged from 20 to 46 species across 6 to 8 phyla (only the reads at the “Tank” were less than 0.001%). The number of non-brittle star species and reads at 80 m was less than 10% with both of the primer sets. These findings suggest that 16SOph1 is specific to the brittle star and 16SOph2 is suitable for a variety of marine metazoans. It appears, however, that further optimization of primer sequences would still be necessary to avoid possible PCR dropouts from eDNA extracts. Moreover, a detailed elucidation of the brittle star fauna in the examined area, and the accurate identification of brittle star species in the current DNA databank is required

Molecular Phylogeny of the Genus Nipponnemertes (Nemertea: Monostilifera: Cratenemertidae) and Descriptions of 10 New Species, With Notes on Small Body Size in a Newly Discovered Clade

Nemerteans, or ribbon worms, have been reported from intertidal to hadal depths, often showing bathymetrically wide distribution in genus levels. Although current nemertean systematics practices require to provide DNA sequences and infer phylogenetic relationships with suitable molecular markers, previous molecular systematics on nemerteans are mostly biased toward shallow-water species. Members in the genus Nipponnemertes occur worldwide, from tropical to polar waters and intertidal to bathyal waters. Molecular phylogenetic studies are scarce for the genus; only six shallow-water species of 18 species in the genus were subject to molecular phylogeny. Thus, Nipponnemertes is one candidate that needs to be assessed by genetic approaches. In this study, we performed molecular phylogenetic analyses using 59 specimens in 23 species based on partial sequences of two mitochondrial (16S rRNA and cytochrome c oxidase subunit I) and three nuclear gene markers (18S rRNA, 28S rRNA, and histone H3). Our extensive sampling from intertidal to bathyal waters in the Northwest Pacific significantly updated the fauna of Nipponnemertes in this region from four to 17 species. We herein establish 10 new species and provide an updated species list concisely summarizing all the congeners known from the world. Our phylogenetic tree indicated three major lineages within the genus (herein referred to as “Clade A, B, and C”), each presumably characterized by the combination of morphological characters in the head region. Members in Clade A are: Nipponnemertes pulchra (Johnston, 1837), Nipponnemertes ogumai (Yamaoka, 1947), and several unidentified congeners, characterized by having demarcated head without cephalic patches; members in Clade B are: Nipponnemertes crypta sp. nov., Nipponnemertes jambio sp. nov., Nipponnemertes neonilae sp. nov., and Nipponnemertes ojimaorum sp. nov., species having demarcated head with cephalic patches; members in Clade C are: Nipponnemertes ganahai sp. nov., Nipponnemertes kozaensis sp. nov., Nipponnemertes lactea sp. nov., Nipponnemertes notoensis sp. nov., Nipponnemertes ornata sp. nov., Nipponnemertes sugashimaensis sp. nov., and two unidentified forms collected off Jogashima (Japan) and Guam (USA), species with non-demarcated head lacking cephalic patches. Furthermore, we discuss the evolution of remarkably small body size retained among Clade C

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

Okanishi, Masanori, Fujita, Toshihiko (2018): A taxonomic review of the genus Astrodendrum (Echinodermata, Ophiuroidea, Euryalida, Gorgonocephalidae) with description of a new species from Japan. Zootaxa 4392 (2): 289-310, DOI: https://doi.org/10.11646/zootaxa.4392.2.

The widely occurring brittlestar Ophiactis savignyi (Amphilepidida: Ophiactidae) as an epibiont on loggerhead sea turtle, Caretta caretta

Hayashi, Ryota, Okanishi, Masanori (2019): The widely occurring brittlestar Ophiactis savignyi (Amphilepidida: Ophiactidae) as an epibiont on loggerhead sea turtle, Caretta caretta. Zootaxa 4695 (5): 497-500, DOI: https://doi.org/10.11646/zootaxa.4695.5.

First finding of anchialine and submarine cave dwelling brittle stars from the Pacific Ocean, with descriptions of new species of Ophiolepis and Ophiozonella (Echinodermata: Ophiuroidea: Amphilepidida)

Okanishi, Masanori, Fujita, Yoshihisa (2018): First finding of anchialine and submarine cave dwelling brittle stars from the Pacific Ocean, with descriptions of new species of Ophiolepis and Ophiozonella (Echinodermata: Ophiuroidea: Amphilepidida). Zootaxa 4377 (1): 1-20, DOI: https://doi.org/10.11646/zootaxa.4377.1.

A comprehensive taxonomic list of brittle stars (Echinodermata: Ophiuroidea) from submarine caves of the Ryukyu Islands, southwestern Japan, with a description of a rare species, Dougaloplus echinatus (Amphiuridae)

Okanishi, Masanori, Fujita, Yoshihisa (2019): A comprehensive taxonomic list of brittle stars (Echinodermata: Ophiuroidea) from submarine caves of the Ryukyu Islands, southwestern Japan, with a description of a rare species, Dougaloplus echinatus (Amphiuridae). Zootaxa 4571 (1): 73-98, DOI: https://doi.org/10.11646/zootaxa.4571.1.

Growth in two deep-sea associates: the octocoral Pseudogorgia bellona and the euryalid snake star Asteroschema ajax

International audiencethe deep-sea octocoral Pseudochrysogorgia bellona was recently described from specimens sampled on the Chesterfield Plateau, off New Caledonia. It is morphologically and genetically similar to the con-familial Metallogorgia melanotrichos, which is known to closely associate with a species of brittle star, Ophiocreas oedipus. these latter two species have never been observed separately and are thought to grow synchronously. the morphological similarity between M. melanotrichos and P. bellona makes the latter another possible host for ophiuroids. however, no brittle star was associated with P. bellona specimens from the type collection. In 2017, 130 P. bellona colonies were sampled near the type locality, and 98% were associated with Asteroschema ajax, a species closely related to O. oedipus. Mitochondrial DNA analysis confirmed the morphological identifications of both P. bellona and A. ajax. Uni-and multivariate statistical analyses were used to characterize the morphological space of both species to test if larger ophiuroids are associated with larger corals. two variables were measured to estimate the size of the coral (total height and diameter of the skeletal axis at its base) and 9 variables were used to characterize the brittle star (disc and arm morphology). Morphological variables representing the size for both species were significantly correlated (Spearman rank correlation coefficient: 50%, p < 0.001), suggesting that larger ophiuroids indeed associate with larger corals. this is one of the rare studies that allowed comparison of growth in associated deep-sea invertebrates