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

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. [ABSTRACT FROM AUTHOR]