Pagurixus dissimilis, Osawa, Masayuki & Komai, Tomoyuki, 2007

Osawa, Masayuki & Komai, Tomoyuki, 2007, A new hermit crab species of the Pagurixus anceps group (Crustacea: Decapoda: Anomura: Paguridae) from southern Japan, and supplemental notes on P. patiae Komai, 2006, Zootaxa 1627, pp. 41-51 : 49-50

Distribution of Pagurixus species in Japan

Thanks to the recent taxonomic studies ( Komai & Myorin 2005; Komai 2006; Komai & Osawa 2006, 2007; Komai & Takada 2006; Osawa et al. 2006), our knowledge on the fauna of Pagurixus hermit crabs has been enriched, although it is likely that many more unknown forms await discovery. Sixteen Pagurixus species, including the new species in this study, are now known from Japan. All species occur in warm temperate, subtropical, and tropical zones, categorized by Nishimura (1992). According to the distributional pattern, the Japanese species can be roughly divided into three groups. The first group consists of species chiefly distributed in the Ryukyu Islands, some of which extend to north along the Pacific coast of the Japanese mainland and along with the Kuroshio Current, or even to the Izu-Ogasawara Islands. These include P. anceps , P. c a r i n i - manus, P. concolor , P. dissimilis n. sp., P. haigae , P. longipes , P. maorus , P. nanus , P. nomurai , P. patiae , P. pseliophorus , P. pulcher , and P. r u b e r. Among them, P. anceps , P. carinimanus , P. concolor , P. haigae , P. maorus , P. nomurai , and P. ruber , are widespread in the Indo-West Pacific or western Pacific. The second group includes species occurring in the Izu-Ogasawara Arc, viz., P. boninensis , P. brachydactylus , and P.

tweediei . Particularly, P. t w e e d i e i is common in subtidal zone in the Ogasawara Islands (our unpublished observation). Pagurixus tweediei does not appear to occur in the Ryukyu Islands, although it is widely distributed in the Indo-West Pacific. The third group comprises only P. fasciatus , which appears restricted to the Izu Islands and the southwestern part of the Japanese mainland (Okuno et al. 2006). It should be noted, however, that a mixture of species from these three groups occurs on the Pacific coast of the southwestern Japanese mainland. According to Nishimura (1992), the Ryukyu and Ogasawara Islands are both referred to the tropical zone. The faunal composition of Pagurixus , however, is quite different as also shown in other shallow-water invertebrates such as porcellanid crabs and gastropod molluscs ( Asakura 1991; Fukuda 1994). These different patterns of distribution suggest that Pagurixus species have different strategies of larval dispersal and habitat selection.