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Tokudaia
''Tokudaia'' is a genus of murine rodent native to Japan. 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''). Of the three species, both ''T. osimensis'' and ''T. tokunoshimensis'' have lost their Y chromosome and ''SRY'' gene; the sex chromosomes of ''T. muenninki'', on the other hand, are abnormally large. Named species 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. See also * ''Ellobius ''Ellobius'' is a genus of rodents in the family Cricetidae. It contains two ('' E. talpinus'' and '' E. tancrei'') of the handful of examples of mammal species that have lost the Y chromosome The Y chromosome is one of two sex chrom ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tokunoshima Spiny Rat
The Tokunoshima spiny rat (''Tokudaia tokunoshimensis'') is a rodent found only on the island of Tokunoshima in the Satsunan Islands of Japan. Due to its small habitat, it is considered endangered. It is commonly found in the secondary and primary subtropical moist broadleaf forests of this island. The karyotype has an odd diploid number, 2n = 45. Like its relative '' T. osimensis'', it is one of the few mammals that lack a Y chromosome and ''SRY'' gene. The species is threatened by deforestation Deforestation or forest clearance is the removal and destruction of a forest or stand of trees from land that is then converted to non-forest use. Deforestation can involve conversion of forest land to farms, ranches, or urban use. Ab ... and predation by feral cats and dogs. See also * '' Ellobius lutescens'' * '' Ellobius tancrei'' References Tokudaia Endemic mammals of Japan Endemic fauna of the Ryukyu Islands Mammals described in 2006 {{Murinae-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Muennink's Spiny Rat
Muennink's spiny rat or Okinawa spiny rat (''Tokudaia muenninki'', or ) is a species of rodent in the family Muridae. Endemic to Okinawa Island, Japan, its natural habitat is subtropical moist broadleaf forest. The karyotype has 2n = 44. Its sex chromosomes are abnormally large, while the other two species in ''Tokudaia'' have lost their Y chromosome. It is found only on the northern part (Yanbaru area) of the island, above 300 m, and is thought to inhabit an area of less than 3 km2. The head and body are up to 7 inches long with a 5-inch tail. They weigh up to 7 ounces. They have a short thick body and dense fur, consisting of fine hairs and coarse, grooved spines (hence the common name “spiny rat”). The fur is brownish above and grayish white below with a faint orange tinge. The spines on the animal's back are black throughout while the spines underneath are usually white with a reddish-brown tip. The spines cover the body except for the regions around the mouth, ears ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 Islands, Ryukyu archipelago of Japan, its natural habitat is subtropical moist broadleaf forest. The karyotype has an odd diploid number, 2n = 25. Like its relative ''Tokudaia tokunoshimensis, T. tokunoshimensis'', it has lost its Y chromosome and SRY gene, ''SRY'' gene. The species is threatened by habitat destruction and habitat fragmentation, fragmentation, predation by feral cats and dogs and introduced species, introduced Herpestes auropunctatus, mongooses, and competition with introduced black rats. See also * ''Ellobius lutescens'' * ''Ellobius tancrei'' References Y-chromosome - Will it or will it not, hold on? Rats of Asia Endemic mammals of Japan Endemic fauna of the Ryukyu Islands Endangered fauna of Asia Tokudaia Mammals described in 1934 Taxonomy articles created by Polbot {{Murinae-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 Y chromosome causes offspring produced in sexual reproduction to be of male sex. In mammals, the Y chromosome contains the SRY gene, which triggers development of male gonads. The Y chromosome is passed only from male parents to male offspring. Overview Discovery The Y chromosome was identified as a sex-determining chromosome by Nettie Stevens at Bryn Mawr College in 1905 during a study of the mealworm ''Tenebrio molitor''. Edmund Beecher Wilson independently discovered the same mechanisms the same year, working with Hemiptera. Stevens proposed that chromosomes always existed in pairs and that the smaller chromosome (now labelled "Y") was the pair of the X chromosome discovered in 1890 by Hermann Henking. She realized that th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Murinae
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 except the Cricetidae and Muridae, and is larger than all mammal orders except the bats and the remainder of the rodents. Description The Murinae are native to Africa, Europe, Asia, and Australia. They are terrestrial placental mammals. They have also been introduced to all continents except Antarctica, and are serious pest animals. This is particularly true in island communities where they have contributed to the endangerment and extinction of many native animals. Two prominent murine species have become vital laboratory animals: the brown rat and house mouse are both used as medical subjects. The murines have a distinctive molar pattern that involves three rows of cusps instead of two, the primitive pattern seen most frequently ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ellobius
''Ellobius'' is a genus of rodents in the family Cricetidae. It contains two ('' E. talpinus'' and '' E. tancrei'') of the handful of examples of mammal species that have lost the 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 .... The genus has the following species: * Alai mole vole (''Ellobius alaicus'') * Northern mole vole (''Ellobius talpinus'') * Zaisan mole vole (''Ellobius tancrei'') Two members of this genus were moved to the genus '' Bramus'': * Southern mole vole (''Bramus fuscocapillus'') * Transcaucasian mole vole (''Bramus lutescens'') See also *'' Tokudaia'' another mammal genus that has lost the Y-chromosome References Rodent genera Taxa named by Gotthelf Fischer von Waldheim Taxonomy articles created by Polbot {{Arvicolinae-s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 being derived from the Greek ἀπό-δημος (literally ''away from home''). Taxonomy Related to the Ryūkyū spiny rats (''Tokudaia'') and the prehistoric ''Rhagamys'' – and far more distantly to ''Mus (genus), Mus'' and ''Malacomys'' – it includes these species: ''Apodemus sensu stricto'' * Striped field mouse, ''A. agrarius'' * Small Japanese field mouse, ''A. argenteus'' * Chevrier's field mouse, ''A. chevrieri'' ''Alsomys'' * South China field mouse, ''A. draco'' * Himalayan field mouse, ''A. gurkha'' * Sichuan field mouse, ''A. latronum'' * Korean field mouse, ''A. peninsulae'' * Taiwan field mouse, ''A. semotus'' * Large Japanese field mouse, ''A. speciosus'' ''Sylvaemus'' * Alpine field mouse, ''A. alpicola'' * Y ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pleistocene
The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was finally confirmed in 2009 by the International Union of Geological Sciences, the cutoff of the Pleistocene and the preceding Pliocene was regarded as being 1.806 million years Before Present (BP). Publications from earlier years may use either definition of the period. The end of the Pleistocene corresponds with the end of the last glacial period and also with the end of the Paleolithic age used in archaeology. The name is a combination of Ancient Greek () 'most' and (; Latinized as ) 'new'. The aridification and cooling trends of the preceding Neogene were continued in the Pleistocene. The climate was strongly variable depending on the glacial cycle, oscillating between cold Glacial period, glacial periods and warmer Interglacial, int ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rodent Genera
Rodents (from Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ... , '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 species are rodents. They are native to all major land masses except for Antarctica, and several oceanic islands, though they have subsequently been introduced to most of these land masses by human activity. Rodents are extremely diverse in their ecology and lifestyles and can be found in almost every terrestrial habitat, including human-made environments. Species can be arboreal, fossorial (burrowing), saltatorial/ricochetal (leaping on their hind legs), or semiaquatic. However, all rodents shar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 other, further blurring any distinctions. Terms that are sometimes used synonymously but have more precise meanings are cryptic species for two or more species hidden under one species name, sibling species for two (or more) species that are each other's closest relative, and species flock for a group of closely related species that live in the same habitat. As informal taxonomic ranks, species group, species aggregate, macrospecies, and superspecies are also in use. Two or more taxa that were once considered conspecific (of the same species) may later be subdivided into infraspecific taxa (taxa within a species, such as plant varieties), which may be a complex ranking but it is not a species complex. In most cases, a species complex is a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SRY Gene
Sex-determining region Y protein (SRY), or testis-determining factor (TDF), is a DNA-binding protein (also known as gene-regulatory protein/transcription factor) encoded by the ''SRY'' gene that is responsible for the initiation of male sex determination in therian mammals ( placentals and marsupials). ''SRY'' is an intronless sex-determining gene on the Y chromosome. Mutations in this gene lead to a range of disorders of sex development with varying effects on an individual's phenotype and genotype. SRY is a member of the SOX (SRY-like box) gene family of DNA-binding proteins. When complexed with the steroidogenic factor 1 (SF-1) protein, SRY acts as a transcription factor that causes upregulation of other transcription factors, most importantly SOX9. Its expression causes the development of primary sex cords, which later develop into seminiferous tubules. These cords form in the central part of the yet-undifferentiated gonad, turning it into a testis. The now-induced L ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
