Kouki Fukuoka

A revision of East Asian Acanthomysis (Crustacea: Mysida: Mysidae) and redefinition of Orientomysis, with description of a new species

Twenty species of Acanthomysis s. l., distributed in Japanese, Korean and Chinese coastal waters, are revised. These species are distinguished from Acanthomysis s. str. by the following characters: the carpopropodus of the endopod of the third to eighth thoracic limbs divided into three to eight subsegments; the exopod of the fourth male pleopod with two long subequal terminal setae; the telson long linguiform or triangular without basal dilated portion and armed with spines throughout margins. On the basis of these characters, the genus Orientomysis, which was revived by Holmquist (1981b) and comprised O. japonica and O. mitsukurii, is redefined and recognized to contain the following 18 valid species: O. aokii, O. aspera, O. crassispinosa, O. fujinagai, O. hwanhaiensis, O. koreana, O. leptura, O. meridionalis, O. okayamaensis, O. pseudomitsukurii, O. robusta, O. rotundicauda, O. sagamiensis, O. serrata, O. sheni, O. tamurai, O. tenella, and O. tenuicauda. Acanthomysis longicauda and A. nakazatoi are synonymized with O. rotundicauda and O. japonica, respectively. A new species, O. arenaria, is described from Japan.

A New Species of Heteromysis (Mysida, Mysidae) Associated with Sponges, from the Uraga Channel, Central Japan, with Notes on Distribution and Habitats within the Genus Heteromysis

A new species, Heteromysis komaii , is described from specimens obtained from the gastral cavity of sponges, Callyspongia confoederata , from the Uraga Channel, located at the entrance of Tokyo Bay, central Japan. Heteromysis komaii is distinguished from all known species of the genus by several features: the distal segment of the antennular peduncle has a flagellate spine at the inner distal angle, the antennal scale is longer than the antennal peduncle, the endopod of the third thoracopod has two flagellate spines at the inner distal angle of the carpus, the fourth to eighth thoracopodal endopods have the carpopropodus divided into two or three subsegments, the male pleopod is unmodified, the uropodal endopod is without spines, the telson has spines on the distal half of the lateral margin, and the apical cleft of the telson is with spinules throughout. The distribution and habitats of the species of Heteromysis are reviewed.

Taxonomy of the genus Meterythrops (Crustacea: Mysida: Mysidae), with a redescription of M. microphthalmus and descriptions of two new species

A taxonomic revision of the genus Meterythrops is provided, including a redescription of M. microphthalmus and newly reported characters of M. japonicus, M. pictus, and M. robustus. Adult males of all species (excluding M. japonicus and M. megalops because no adult males of these species have been collected) have pleopods with modified setae, which are found on the fifth pleopod in M. microphthalmus and M. robustus, and on the fourth and fifth pleopods in M. pictus. Two new species, M. intermedius and M. tenuispinis, from Alaskan and East Asian waters, respectively, are also described. Males of both species also have modified setae on the fifth pleopod. Meterythrops microphthalmus and M. robustus are recorded for the first time from Alaskan waters and Japanese waters, respectively.

A new genus for Acanthomysis schrencki (Czerniavsky, 1882) (Crustacea: Mysida: Mysidae) with the first description of the male

A new genus, Boreoacanthomysis, is established for the reception of Acanthomysis schrencki. The new genus is characterized by the fourth male pleopod armed with a pair of long plumose setae at the distal end of the proximal segment of the exopod, and by the uropodal endopod armed with about 30 spines near the statocyst. The male of this species is described for the first time.

A REVISION OF THE GENUS PARASTILOMYSIS (MYSIDA: MYSIDAE), WITH DESCRIPTIONS OF THREE NEW SPECIES AND ESTABLISHMENT OF A NEW GENUS FOR P. SECUNDA

Abstract Three new species of Parastilomysis, P. paucispina, P. prominula, and P. separata, are described from Japanese waters. Parastilomysis paucispina is different from the other species of the genus by the smaller body size and the uropodal endopod with the inner margin armed with fewer spines, P. prominula by two small protuberances on the mid-dorsal line of the carapace, and P. separata by the arrangement of spines on the lateral margin of the telson. Parastilomysis secunda is revised taxonomically, and a new genus, Hyperstilomysis, is proposed for the accommodation of this species.