Polycopsis higejii sp. nov. (Crustacea: Ostracoda) from a Sandy Beach in Central Japan

Abstract

A new species of the ostracod genus Polycopsis G. W. Müller, 1894 (Myodocopa: Halocyprida: Polycopidae), P. higejii sp. nov., is described from the interstitial habitat of a sandy beach in Miura City, central Japan. This is the first record of the genus from a sandy beach interstitial environment. The new species is characterized by a broadly suboval carapace with approximately 20 serrations along the anterior margin, 16 plumose setae on the branchial plate of the fifth limb, and a straight sword-like ejaculatory duct on the male copulatory organ. The new species most closely resembles P. vietnamiensis Chavtur, 1983 in carapace morphology and appendage chaetotaxy, but differs in the length of ventral setae on the third podomere of antennula and the number of epipodial setae on the fifth limb. Partial nucleotide sequences of the 18S rRNA gene and Internal Transcribed Spacer regions were obtained for future phylogenetic and systematic studies. In addition, diagnostic characters distinguishing Polycopsis and Metapolycope Kornicker and Morkhoven, 1976 are reexamined, and M. duplex Kornicker and Iliffe, 1989 is transferred to Polycopsis as P. duplex comb. nov. The discovery of this new species from a common recreational beach suggests that the diversity of interstitial meiobenthos in Japan remains insufficiently explored.