Apseudes ranma sp. nov. (Tanaidacea: Apseudidae) found in a public aquarium, with notes on phylogeny and a presumptive stridulatory organ

Abstract

We describe Apseudes ranma sp. nov. from the Port of Nagoya Public Aquarium, Nagoya, Japan. It resembles two congeners, Apseudes curtiramus (Guţu, 2007) and Apseudes orghidani Guţu and Iliffe, 1989, in having the rostrum triangular, wider than long, the carapace without lateral spines, distinct and round eye lobes, pereonites 3–6 with a pair of tongue-shaped anterolateral projections, and the pleotelson with two pairs of lateral projections, but differs from them in having lateral setae on the anterolateral margin of the carapace and a ventro-subproximal spine on the pereopod-1 basis, and in the number of spiniform setae on articles of pereopods 2–4. We determined partial nucleotide sequences for the cytochrome c oxidase subunit I (COI) and 18S rRNA (18S) genes in A. ranma sp. nov. for future DNA barcoding and phylogeny reconstruction. In an 18S tree, A. ranma sp. nov. was the sister taxon to Apseudes nipponicus Shiino, 1937, and this clade was the sister group to moderately supported Carpoapseudes clade. We discovered a presumptive stridulatory organ in A. ranma sp. nov. consisting of a cylindrical protrusion and knobbly area on the inner surface of each of the left and right chelipedal bases. The location of the protrusion and knobbly area suggests that these may be a plectrum and pars stridens, respectively.