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Tokudaia Tokunoshimensis
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 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 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. The most concentrated ... 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] |
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 native to all major land masses except for New Zealand, 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/richochetal (leaping on their hind legs), or semiaquatic. However, all rodents share several morphological features, including having only a single upper and lower pair of ever-growing incisors. Well-known rodents include mice, rats, squirrels, prairie dogs, porcupines, beavers, guinea pigs, and hamsters. Rabbits, hares, and pikas, wh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 absence of Y that determines the male or female sex of offspring produced in sexual reproduction. In mammals, the Y chromosome contains the gene SRY, which triggers male development. The DNA in the human Y chromosome is composed of about 59 million base pairs, making it similar in size to chromosome 19. The Y chromosome is passed only from father to son. With a 30% difference between humans and chimpanzees, the Y chromosome is one of the fastest-evolving parts of the human genome. The human Y chromosome carries an estimated 100–200 genes, with between 45 and 73 of these being protein-coding. All single-copy Y-linked genes are hemizygous (present on only one chromosome) except in cases of aneuploidy such as XYY syndrome or XXYY syndrome. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Endemic Mammals Of Japan
Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsewhere. For example, the Cape sugarbird is found exclusively in southwestern South Africa and is therefore said to be ''endemic'' to that particular part of the world. An endemic species can be also be referred to as an ''endemism'' or in scientific literature as an ''endemite''. For example '' Cytisus aeolicus'' is an endemite of the Italian flora. '' Adzharia renschi'' was once believed to be an endemite of the Caucasus, but it was later discovered to be a non-indigenous species from South America belonging to a different genus. The extreme opposite of an endemic species is one with a cosmopolitan distribution, having a global or widespread range. A rare alternative term for a species that is endemic is "precinctive", which applies to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 is the only member of the tribe Ellobiusini. It contains two ('' E. lutescens'' and '' E. tancrei'') of the handful of examples of mammal species that have lost the Y chromos ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ellobius Tancrei
The Zaisan mole vole (''Ellobius tancrei''), or eastern mole vole, is a species of rodent in the family Cricetidae. It is found in central Asia. Description The Zaisan mole vole is highly adapted to life underground. It grows to a head and body length of with a short tail long and weighs between . The coat is dense, soft and velvety. The face and the crown of the head are dark brown and the external ears are reduced to a fleshy ridge. The incisors are pure white, straight and long and project forward in front of the snout. The dorsal surface of the body varies in colour from sandy brown to dark greyish brown and the underparts vary from white to greyish brown. The tail is sandy brown and is tipped with a tuft of greyish-white hair. The hands and feet are broad, have small claws and are covered with white hairs. Chromosomes The karyotype is variable, with 2n = 32-54. The Y chromosome has been lost, similar to the case of '' E. lutescens''; however, unlike in ''E. lutescens'', b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ellobius Lutescens
The Transcaucasian mole vole (''Ellobius lutescens'') is a species of rodent in the family Cricetidae. It is found in Armenia, Azerbaijan, Georgia, Iran, and Turkey. Chromosomes The karyotype has a low, odd, diploid number, 2n = 17,X. Transcaucasian mole voles have no ''SRY'' gene or Y chromosome; both sexes have an XO sex chromosome set, a state possibly derived from an ancestral population in which males had an XX sex chromosome set, like '' E. tancrei''. Their sex-determination method remains unknown. See also *Zaisan mole vole *'' Tokudaia osimensis'' *''Tokudaia tokunoshimensis 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 ...'' References Ellobius Rodents of Asia Vole, Transcaucasian Mole Mammals of Azerbaijan Mole Vole, Transcaucasian South Caucasus Mammal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Deforestation
Deforestation or forest clearance is the removal 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. The most concentrated deforestation occurs in tropical rainforests. About 31% of Earth's land surface is covered by forests at present. This is one-third less than the forest cover before the expansion of agriculture, a half of that loss occurring in the last century. Between 15 million to 18 million hectares of forest, an area the size of Bangladesh, are destroyed every year. On average 2,400 trees are cut down each minute. The Food and Agriculture Organization of the United Nations defines deforestation as the conversion of forest to other land uses (regardless of whether it is human-induced). "Deforestation" and "forest area net change" are not the same: the latter is the sum of all forest losses (deforestation) and all forest gains (forest expansion) in a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tokudaia Osimensis
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. The karyotype has an odd diploid number, 2n = 25. Like its relative '' T. tokunoshimensis'', it has lost its Y chromosome and ''SRY'' gene. The species is threatened by habitat destruction and fragmentation, predation by feral cats and dogs and introduced mongooses, and competition with introduced black rats. See also * ''Ellobius lutescens'' * ''Ellobius tancrei The Zaisan mole vole (''Ellobius tancrei''), or eastern mole vole, is a species of rodent in the family Cricetidae. It is found in central Asia. Description The Zaisan mole vole is highly adapted to life underground. It grows to a head and body ...'' References Y-chromosome - Will it or will it not, hold on? Rats of Asia Endemic mammals of Japan Endemic fauna of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tokunoshima
, also known in English as is an island in the Amami archipelago of the southern Satsunan Islands of Kagoshima Prefecture, Japan. The island, in area, has a population of approximately 27,000. The island is divided into three administrative towns: Tokunoshima, Isen, and Amagi. The largest population center on the island is the town of Kametsu, located along the eastern shore of the island within the administrative town of Tokunoshima. Much of the island is within the borders of Amami Guntō National Park. The island is known for having the highest birth rates in Japan as well as a significant population of supercentenarians (people living significantly beyond the age of 100). Geography Tokunoshima is the second largest island in the Amami islands, after Amami Ōshima, and the 15th largest island in Japan. It is more generally included within the Satsunan and Ryukyu archipelagos. Isolated from the other Amami islands, Tokunoshima is located halfway between Amami Ōshima ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diploid
Ploidy () is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Sets of chromosomes refer to the number of maternal and paternal chromosome copies, respectively, in each homologous chromosome pair, which chromosomes naturally exist as. Somatic cells, tissues, and individual organisms can be described according to the number of sets of chromosomes present (the "ploidy level"): monoploid (1 set), diploid (2 sets), triploid (3 sets), tetraploid (4 sets), pentaploid (5 sets), hexaploid (6 sets), heptaploid or septaploid (7 sets), etc. The generic term polyploid is often used to describe cells with three or more chromosome sets. Virtually all sexually reproducing organisms are made up of somatic cells that are diploid or greater, but ploidy level may vary widely between different organisms, between different tissues within the same organism, and at different stages in an organism's life cycle. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Karyotype
A karyotype is the general appearance of the complete set of metaphase chromosomes in the cells of a species or in an individual organism, mainly including their sizes, numbers, and shapes. Karyotyping is the process by which a karyotype is discerned by determining the chromosome complement of an individual, including the number of chromosomes and any abnormalities. A karyogram or idiogram is a graphical depiction of a karyotype, wherein chromosomes are organized in pairs, ordered by size and position of centromere for chromosomes of the same size. Karyotyping generally combines light microscopy and photography, and results in a photomicrographic (or simply micrographic) karyogram. In contrast, a schematic karyogram is a designed graphic representation of a karyotype. In schematic karyograms, just one of the sister chromatids of each chromosome is generally shown for brevity, and in reality they are generally so close together that they look as one on photomicrographs as well ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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