''Tokudaia'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

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 (biology), order Rodentia ( ), which are characterized by a single pair of continuously growing incisors in each of the upper and Mandible, lower jaws. About 40% of all mammal specie ...

native to

Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...

. 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, murid (true mice and rats) containing the field mice as well as other well-known species like the wood mouse and the yellow-necked mouse. The name is unrelated to that of the ''Mus (genus), Mus'' genus, instead ...

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

Y chromosome The Y chromosome is one of two sex chromosomes in therian mammals and other organisms. Along with the X chromosome, it is part of the XY sex-determination system, in which the Y is the sex-determining chromosome because the presence of the ...

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

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

are: * Muennink's spiny rat, ''Tokudaia muenninki'' * Ryukyu spiny rat, ''Tokudaia osimensis'' * Tokunoshima spiny rat, ''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