''Tokudaia'' is a genus of

murine The Old World rats and mice, part of the subfamily Murinae in the family Muridae, comprise at least 519 species. Members of this subfamily are called murines. In terms of species richness, this subfamily is larger than all mammal families excep ...

rodent Rodents (from Latin , 'to gnaw') are mammals of the order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents. They are na ...

native to

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...

. Known as Ryūkyū spiny rats or spinous country-rats, population groups exist on several non-contiguous islands. Despite differences in name and appearance, they are the closest living relatives of the Eurasian field mouse (''

Apodemus ''Apodemus'' is a genus of Muridae (true mice and rats). The name is unrelated to that of the '' Mus'' genus, instead being derived from the Greek ἀπό-δημος (literally ''away from home''). Taxonomy Related to the Ryūkyū spiny rat ...

''). Of the three species, both ''T. osimensis'' and ''T. tokunoshimensis'' have lost their

Y chromosome The Y chromosome is one of two sex chromosomes (allosomes) in therian mammals, including humans, and many other animals. The other is the X chromosome. Y is normally the sex-determining chromosome in many species, since it is the presence or abse ...

and ''SRY'' gene; the sex chromosomes of ''T. muenninki'', on the other hand, are abnormally large. Named

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

are: * Muennink's spiny rat, ''Tokudaia muenninki'' *

Ryukyu spiny rat The Ryukyu spiny rat (''Tokudaia osimensis'') is a species of rodent in the family Muridae. Endemic to Amami Ōshima island in the Amami Islands of the Ryukyu archipelago of Japan, its natural habitat is subtropical moist broadleaf forest. Th ...

, ''Tokudaia osimensis'' *

Tokunoshima spiny rat The Tokunoshima spiny rat (''Tokudaia tokunoshimensis'') is a rodent found only on the island of Tokunoshima in the Ryukyu Islands of Japan. Due to its small habitat, it is considered endangered. It is commonly found in the secondary and primary ...

, ''Tokudaia tokunoshimensis'' At least ''Tokudaia osimensis'' may be a

cryptic species complex In biology, a species complex is a group of closely related organisms that are so similar in appearance and other features that the boundaries between them are often unclear. The taxa in the complex may be able to hybridize readily with each oth ...

References

Rodent genera Endemic mammals of Japan Endemic fauna of the Ryukyu Islands {{Murinae-stub

See also

References