Allocricetulus

Means Great Dwarf Hamster ( Allocricetulus ) constitute a genus of hamsters with the types Eversmann dwarf hamsters and Mongolian dwarf hamsters. Some taxonomists assign them to the Grey dwarf hamsters. They are widespread in the arid steppes of Eurasia and known fossil from the Pleistocene. The World Conservation Union IUCN classifies them as not at risk.

Body characteristics

The head-body length of the central Great Dwarf Hamster is from 8.5 to 16.0 inches. The tail is in contrast to the gray dwarf hamster as long as the hind paws or only slightly longer and its length is no more than a fifth of the body length. From the hairy tail rich individual guard hairs half the length of tail back and let the tail appear conical. The snout is pointed, but less than in the rat -like dwarf hamsters. The ears are relatively short, covered without bordered lightly and evenly with thin hair.

The soles of the Central Great Dwarf hamsters are in contrast to those of the short-tailed dwarf hamster usually not covered by fur or sparsely hairy. However, the pronounced bales can be hidden in the winter Sohlenbehaarung. On the front paw, the claw of the first toe has often in the form of a nail and the fifth toe is comparatively much shorter. The skin of the top is dull gray-brown to reddish- sandy color. Unlike the short-tailed dwarf hamsters it is usually clearly distinguished from the white of the underside. Is a patch on the chest is available, this is not black. The winter coat color does not differ from the summer coat.

In the structure of the skull which means Great Dwarf hamsters are very similar to large hamsters and they occupy an intermediate position between the gray dwarf hamsters and the means hamsters. The nearly circular skull is rounder than the Grey dwarf hamsters, the muzzle is shorter and the span between the zygomatic arches is greater. The zygomatic arches are thin, rounded and only run in the middle part more or less parallel to each other. The nasal bones are wedge-shaped with a strongly convex front and a pronounced indentation along the nose leg seam. In older hamsters this depression is more pronounced and continues up to the brow bone and along the orbits.

Instead of merely indicated in the gray dwarf hamsters hump have older Medium dwarf hamster on the orbits between the frontal bone and the different in length, anterior extension of the parietal bone on bone pronounced hump. Bone strips between the frontal and parietal bone, in contrast to most hamsters do not exist or they are weak and do not approach each other along the coronal suture on. At the outer edge of the parietal bone are rounded bars, ranging from the orbits to the occiput. Approach as in the rat -like dwarf hamsters this in the middle also not at each other and give the skull its angular shape. The intermediate parietal bone is crescent shaped. Having a width which is at least two times its length, it is relatively shorter than that of the bulk hamsters. The original surface of the masseter muscle on the upper jaw bone is compared to the same area in the United hamsters, especially above less angled inwards and its front wall covered is usually not the lower eye hole. With less than 40 millimeters in length, the Condylobasallänge is shorter than for larger hamsters. The bullae are larger than those of the gray dwarf hamsters and the wing of the sphenoid bone pits are slightly narrower. They extend forward to the level of the last molar tooth.

The branches of the lower jaw are more pronounced than in the rat -like dwarf hamsters, steeply curved upwards and the rear tip usually goes back to the height of the condyle. The increase in the alveoli is usually at the level of the incision between muscle and joint extension. Unlike most hamsters it is pronounced, ranging in older hamsters up to the amount back to the top of the condylar process. The groove along the outside of the mandible is pronounced.

Teeth

The lower incisors of the Great Dwarf hamster means are strong and steeply curved upwards. The paired cusps of the anterior upper molars are like the dwarf hamsters dread facing each other. The first lower molar opposite to each other as well, but are located between the cusps, apart from the central cusps of a European style, no closed depressions. The second lower molar tooth cusps are offset from each other. The small, about the same size front tooth cusp of the first upper molar tooth are clearly separated from the next pair and comparatively strongly shifted to the outside. The anterior cusp of the first lower molar are also approximately the same size, but hardly separated.

The "collar" on the first and second upper molars are weak. The second molar tooth, the inner and the outer collar as the same size, the third of the inner collar is often not available. The third upper molar is about half as long as the second and third lower molar is about three quarters the length of the second.

Body skeleton

In the construction of the limbs and sacrum which means Great take dwarf hamster an intermediate position between the gray dwarf hamsters and the means hamsters. It is characterized by the presence of a slightly flattened above, clearly contrasting bone bump on the ilium. The femur has a long neck and an enlarged little rolling hills, whose lower edge stands out clearly from the bone shaft. The Elle is relatively short, in comparison to large hamsters, long upper and lower ends and a little pronounced, flattened stem.

Genetics

According Romanenko and employees, the assumed original karyotype of the middle Great Dwarf Hamster with 32 chromosomes by a Zentromerfission and four centromere fusions of the supposed original karyotype of Cricetus group differs.

Way of life

The habitat of the Central Great Dwarf hamster is the Eurasian steppe region pflanzengeografische the Palaearctic, outside of which they are not, or almost not to be found. The Mongolian dwarf hamster, and probably the Eversmann dwarf hamster is not tied to specific biotopes or biotope groups and comes in low numbers before almost everywhere. Medium dwarf hamsters prefer the burrows of other rodents and rabbits -like or hiding places to inhabit such as grass clods of plowed fields. Your self -dug construction similar to that of Campbell dwarf hamster. They feed on the seeds of grasses as well as in considerable amounts of animal-derived food and are referred to as "true carnivores ". During the breeding season, which begins even before the melting of the snow, the females bring three to four litters world. In the second half of the summer, the females are already involved from the first litter in reproduction.

Distribution and phylogeny

The distribution area of the Central Great Dwarf hamsters are the dry steppes and semi- deserts of northern Kazakhstan and neighboring Russia east of the Volga and Mongolia and northern China.

The individual species were probably formed during the Pleistocene along the account of climatic conditions propagating westward steppes, the Sayan Mountains and the Altai acted as geographical barriers and allopatric speciation enabled. Molecular genetic studies suggest a source of funds Great Dwarf Hamster in Pliocene. Fossils, however, are known only from the Middle Pleistocene. You are close to the Late Pliocene Allocricetus from Europe or are identical with these. Until the Holocene, the western border of the distribution area of the Central Great Dwarf Hamster of the Dobrogea region of Romania moved further east. This is a typical development for representatives of the Volga fauna.

Nomenclature and systematics

AI Argiropulo out the means Great Dwarf Hamster in 1932 as a subgenus of the genus Allocricetulus Cricetulus with the type species Cricetulus ( Allocricetulus ) eversmanni. The name derives from ancient Greek allos ( αλλος, " strange " ) and the generic name Cricetulus.

Some taxonomists confirmed its status as a subgenus ( Ellerman, 1941; Ellerman and Morrison -Scott, 1951; Ellerman, 1961) and further arranged the means Great Dwarf hamsters of the genus Cricetulus to ( Simpson, 1945; Walker, 1975; Corbet, 1978; Corbet and Hill, 1980; Honacki and staff, 1982; Nowak and Paradiso, 1983; Corbet and Hill, 1986; Grzimek, 1988; Corbet and Hill, 1991; Nowak, 1991). Igor Mikhailovich Gromov led them in 1963 as an independent genus, a view that more and more systematic follow (Flint, 1966; Piechocki, 1969; Gromov and Baranova, 1981; Pawlinow and Rossolimo, 1987; Musser and Carleton, 1993; Gromov and Jerbajewa, 1995, Pawlinow and staff, 1995; McKenna and Bell, 1997; Pawlinow and Rossolimo, 1998; Nowak, 1999; Pawlinow, 2003; Wang, 2003; Musser and Carleton, 2005; Smith and Hoffman, 2008).

Molecular genetic studies of mitochondrial cytochrome b and 12S rRNA genes and the nuclear vWF gene confirm the status as a distinct genus, and the close relationship with the European hamster and to a lesser extent with the horror dwarf hamster and the rat -like hamster. Studies of the chromosomes can, however, suggest a closer relationship with the Sokolow - dwarf hamster. In their sensitivity and susceptibility to infections such as tularemia, the Great Dwarf hamster means differ significantly from other dwarf hamsters and to each other. They are usually divided into two extant species:

• The Eversmann dwarf hamster ( Allocricetulus eversmanni ) in northern Kazakhstan and neighboring Russia and
• The Mongolian dwarf hamster ( Allocricetulus curtatus ) in Mongolia and northern China.

Some taxonomists place the Mongolian dwarf hamster as a subspecies of the Eversmann dwarf hamsters. The two forms differ in the physical characteristics only slightly from each other and there are populations with transitional features in the adjacent area of ​​distribution. The differences in the chromosomes and the resulting apparent genetic isolation suggest, however, to the independence as species.

Medium dwarf hamster and human

The economic importance of the middle Great Dwarf Hamster for humans is low and their significance for epidemics is poorly understood. They are found in rural buildings and dwellings as yurts, storage shed and temporarily abandoned winter camps. As a German common names are " Medium dwarf hamster " ( Honey, 2005; Fox, 2006) and " Mongolian dwarf hamster " ( Macdonald, 2004 ) was used. Very rarely, they are kept in captivity.