A new marine tardigrade genus and species (Arthrotardigrada, Styraconyxidae) with unique pockets on the legs

Shinta Fujimoto,Naoto Jimi

doi:10.3897/zse.96.49676

Abstract

A marine heterotardigrade Cyaegharctus kitamuraigen. et sp. nov. (Arthrotardigrada, Styraconyxidae) is described from Daidokutsu, a submarine cave off Iejima island, Okinawa Islands, Ryukyu Archipelago, Japan. It is easily distinguished from all other styraconyxids by its pocket organs (putative sensory structures) on all legs in addition to the usual leg sensory organs. Its combination of other character states, such as the dorso-ventrally flattened body, ovoid primary clavae, conical secondary clavae, large terminal anus, internal digits with proximal pads and peduncles, external digits with developed peduncles and all digits with three-pointed claws in adult female, supports the erection of a new genus and species.

Highlights

Marine tardigrades, arthrotardigrades, exhibit remarkable morphological diversity (see comprehensive drawings of arthrotardigrade genera in Fontoura et al (2017) and drawings of additional genera in Fujimoto and Yamasaki (2017) and Fujimoto and Ohtsuka (2019))
Fujimoto et al (2017) did not make any remarks on the undescribed genus’ morphology and only provided two voucher micrographs of a specimen used for their molecular phylogenetic study (provided by MorphoBank (O’Leary and Kaufman 2012) at http://doi.org/10.7934/ P2234)
The type material was collected from Daidokutsu, a submarine cave off Iejima island, Okinawa Islands, Ryukyu Archipelago, Japan (26°43'N, 127°50'E) (Yamamoto et al 2009) in 2013 and 2019 by Koshin Yasumura (KY) and the first author (SF)

Summary

Introduction

Arthrotardigrades, exhibit remarkable morphological diversity (see comprehensive drawings of arthrotardigrade genera in Fontoura et al (2017) and drawings of additional genera in Fujimoto and Yamasaki (2017) and Fujimoto and Ohtsuka (2019)). Styraconyxidae Kristensen and Renaud-Mornant, 1983 is one of the arthrotardigrade families and it is comprised of 38 species and subspecies of ten genera: Angursa Pollock, 1979 (eight species), Bathyechiniscus Steiner, 1926 (monotypic), Lepoarctus Kristensen and Renaud-Mornant, 1983 (monotypic), Paratanarctus D’Addabbo Gallo et al, 1992 (monotypic), Pleocola Cantacuzène, 1951 (monotypic), Raiarctus Renaud-Mornant, 1981a (five species), Rhomboarctus Renaud-Mornant, 1984 (three species), Styraconyx Thulin, 1942 (15 species and subspecies), Tetrakentron Cuénot, 1892 (monotypic) and Tholoarctus Kristensen and Renaud-Mornant, 1983 (three species and subspecies) (Guidetti and Bertolani 2005; Degma and Guidetti 2007; Degma et al 2019; Pérez-Pech et al 2020) In addition to these ten genera, Fujimoto et al (2017) reported an undescribed genus related to Styraconyx and Tetrakentron from a submarine cave in Japan (for detail of this cave see Yamamoto et al 2009). We describe this taxon as a new genus and species, based on detailed morphological observation of additional material collected from the same cave

Material and methods

Discussion