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Isopods on isopods: integrative taxonomy of Cabiropidae (Isopoda: Epicaridea: Cryptoniscoidea) parasitic on anthuroid isopods, with descriptions of a new genus and three new species from Japan

Shoki Shiraki , Keiichi Kakui

Abstract

Species in the parasitic isopod family Cabiropidae are known to utilize various isopods as hosts but there are no records of its members parasitizing anthuroid hosts to date. We describe Anthuroniscus gen. nov. for three new cabiropid species, Anthuroniscus shimomurai sp. nov., Anthuroniscus dentatus sp. nov., and Anthuroniscus latus sp. nov., all of which are parasitic on anthuroid isopods. Anthuroniscus gen. nov. differs from the other 14 cabiropid genera and 10 genera treated as family incertae sedis in females having an elongate, dorsally compressed, posteriorly tapering body with six pairs of lateral bulges; and in cryptoniscus larvae by the following combination of characters: (1) eyes lacking, (2) antennular article 1 with eight teeth on the posterior margin, (3) uropodal exopod and endopod rectangular rather than tapering, and endopod longer than exopod, and (4) pleotelson trapezoidal, with the width twice the length. Anthuroniscus shimomurai sp. nov. was parasitic on Mesanthura sp. from Kaichu Doro, Uruma, Okinawa, southwestern Japan; A. dentatus sp. nov. on Accalathura sp. from Irabu Island, Miyako Islands, Okinawa; and A. latus sp. nov. on Colanthura nigra from Kanagawa, central Japan. In pairwise comparisons, the three new species showed p-distances of 0.6–1.3% for the 18S rRNA gene (1440 positions); A. shimomurai sp. nov. and A. latus sp. nov. showed a p-distance of 36.2% for the 16S rRNA gene (412 positions). In an 18S-based maximum-likelihood tree, an Anthuroniscus gen. nov. clade was the sister group to Cryptoniscoidea sp., parasitic on an ostracod species. This is the first study reporting Cabiropidae from Japan and anthuroids as hosts for Cryptoniscoidea.

IS24013  Accepted 10 July 2024

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