Paradoxapseudes shimojiensis sp. nov. (Crustacea: Tanaidacea: Apseudidae) from a submarine limestone cave in Japan, with notes on its chelipedal morphology and sexual system

ABSTRACT

We describe Paradoxapseudes shimojiensis sp. nov. from a submarine limestone cave at Shimoji-jima Island, Ryukyu Islands, southwestern Japan. This species resembles five species (P. basibidens, P. bassoprofundo, P. bermudeus, P. edgari, and P. heroae, among 17 congeners) that bear a long pleotelson, but differs from them in having (i) a naked antennal article 1, (ii) the maxillipedal basis with one inner distal plumose seta, (iii) the chelipedal basis with one dorsodistal and one ventro-subproximal simple setae, (iv) the pereopod-1 basis with four dorsal simple setae longer than the width of the pereopod-1 basis, but without ventrodistal spiniform setae, (v) the pereopod-1 merus with three mid-inner ventral simple setae, and (vi) the pleopodal protopod with two inner plumose setae. We determined partial nucleotide sequences for the cytochrome c oxidase subunit I (COI) and 18S rRNA (18S) genes in P. shimojiensis for future use in DNA barcoding and phylogeny. Paradoxapseudes shimojiensis has serial ridges on the inner surfaces of the left and right chelipedal bases that quite resemble the stridulatory organs in harvestmen (Opiliones); by analogy, we speculate that these ridges may be stridulatory sound-producing organs. Two specimens had both a fully-developed marsupium and genital cone, suggesting that P. shimojiensis is simultaneously hermaphroditic.

http://zoobank.org/urn:lsid:zoobank.org:pub:391C3C0F-8845-4496-A27D-936384F9E59D

KEYWORDS:

• Malacostraca
• Peracarida
• stygophilic
• hermaphrodite
• acoustic
• benthos

Acknowledgements

We thank Masaru Mizuyama, Katrine Worsaae, Peter Rask Møller, Yuji Ise, Hiroki Ichi, Hirotaka Ichi, and Go Tomitani for assistance in scuba sampling in the submarine cave; and Matthew H. Dick for reviewing the manuscript and editing our English.

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Keiichi Kakui http://orcid.org/0000-0003-4630-9065

Additional information

Funding

This study was supported by the Japan Society for the Promotion of Science (JSPS) under KAKENHI grants JP16K18597 and JP19K06800 to KK, and JP16K07490 and JP16H06309 to YF.