[ **up: [[Animals]] | [[Mammals]] | [[Rodents]] | [[Muridae (Family)]] | [[Tokudaia (Genus)]]** ] --- # Ryukyu spiny rat (*Tokudaia osimensis*) --- ## Taxonomy - **[[Life (Biology)]]** - **[[Eukaryotes|Eukaryota (Domain)]]** - [[Animals|Animalia (Kingdom)]] - [[Chordates|Chordata (Phylum)]] - [[Mammals|Mammalia (Class)]] - [[Therians|Theria (Subclass)]] - [[Eutherians|Eutheria (Infraclass)]] - [[Rodents|Rodentia (Order)]] - [[Muridae (Family)]] - *[[Tokudaia (Genus)]]* - *[[Ryuku spiny rat|Tokudaia osimensis]]* <small>RYUKYU SPINY RAT</small> --- ## Description ### Sex determination #### X0 males & X0 females [[2025-0313. 'In mammals, there are indeed a few natural exceptions to the standard XX-XY sex determination system.'|’In mammals, there are indeed a few natural exceptions to the standard XX/XY sex determination system (SDS). For example … both males and females are X0 in the Japanese spiny rat Tokudaia osimensis …’]][^1] > Males and females with an identical XO karyotype (loss of the second X chromosome in females and of the Y in males) in the Japanese spiny rats *Tokudaia osimensis* and *Tokudaia tokunoshimensis*.[^2] ##### Chromosomes In 1977, Takeo Honda (et al.) wrote, “The diploid chromosome number of the Amami spinous country-rat, *Tokudaia osimensis osimensis*, [[2025-0324. 'The diploid chromosome number of the Amami spinous country-rat, Tokudaia osimensis osimensis, was found in this study to be 25 in both sexes, lacking an X in the female and a visible Y in the male.'|was found in this study to be 25 in both sexes, lacking an X in the female and a visible Y in the male.]]”[^3] [^1]: P. A. Saunders, et al., ‘[[Saunders, et al. ‘Masculinised behaviour of XY females in mammal with naturally occurring sex reversal’, 2016.|Masculinised behaviour of XY females in a mammal with naturally occurring sex reversal]]’, *Scientific Reports*, vol. 6 (11 March 2016), p. 1. [^2]: Frederic Veyrunes, et al., ‘[[Veyrunes, et al. 'A novel sex determination system in a close relative of the house mouse', 2010.|A novel sex determination system in a close relative of the house mouse]]’, *Proceedings of the Royal Society B: Biological Sciences*, vol. 277, issue 1684 (7 April 2010), pp. 1049–1050. [^3]: Takeo Honda, et al., ‘[[Honda, et al. ‘An Unusual Sex Chromosome Constitution Found in the Amami Spinous Country-Rat, Tokudaia Osimensis Osimensis’, 1977.|An Unusual Sex Chromosome Constitution Found in the Amami Spinous Country-Rat, Tokudaia Osimensis Osimensis]]’, *Journal of Japanese Genetics*, vol. 52, no. 3 (1977), p. 247.