Tokudaia osimensis (Abe 1933)

[Rattus] jerdoni Abe 1933, Botany and Zoology, Vol. 1: 942.

Type Locality: Japan, Ryukyu Isls (= Nansei Isls), Amami-oshima Isl, Mt Kiyago-kan, village of Sumiyo.

Vernacular Names: Amami-oshima Island Spiny Rat.

Distribution: Known only by modern samples from Amami-oshima Isl.

Conservation: IUCN – Endangered.

Discussion: Abe, 1934, J. Sci. Hiroshima Univ., ser. B, div. 1, 3:107, is the usual date and citation for osimensis (see Corbet and Hill, 1992 and Musser and Carleton, 1993), but the name was proposed a year earlier in a different journal according to Kaneko (2001); also see Kaneko and Maeda (2002).The unique chromosomal complement of this species (2n = 25, with no X in the female or visible Y in the male) first documented by Honda et al. (1977) and corroborated by Kimiyuki et al. (1989). Testes devopment depends upon inheritance of the Sry gene encoded on the Y chromosome, but T. osimensis lacks this gene (Suzuki et al., 1999 b), a phenomenon found elsewhere among murids only in species of the arvicoline Ellobius (Just et al., 1995) . Suzuki et al. (1999 b:590) noted that to describe the mechanism of sex determination in these species "will require a more precise genetic analysis... and will bring us new information on sex determination mechanisms, evolution, and plasticity." Reviewed by Kaneko (1994), who also provided a beautiful color photograph of the live rat.