Phodopus

Roborowski dwarf hamster ( Phodopus roborovskii )

The short-tailed dwarf hamster ( Phodopus ) are a genus of hamsters and include the Roborowski dwarf hamster and Djungarian hamsters. Fossils are known from the Pleistocene in Eurasia. They inhabit the forests, steppes and semi-deserts of Mongolia, southern Siberia and in adjacent areas of China and Kazakhstan and feed mainly on the seeds of plants.

Short-tailed dwarf hamsters are small hamster, does not stick out their short tail from the fur. They have special adaptations to extreme temperatures, such as hairy paws and a special thermoregulation on.

• 4.1 Outer systematics
• 4.2 Internal systematics

Body characteristics

Exterior body features

The body of the short-tailed dwarf hamster is strong and the head-body length is 5.3 to 10.2 centimeters. With 4 to 14 millimeters, the tail length is usually less than a fifth of it, and the hairy tail is shorter than the hind paws. The characteristics of the head resemble those of other dwarf hamsters, the muzzle is shorter, the neck is comparatively weak and short, thin ears are hairy. Bent forward they do not extend to the comparatively large eyes.

The paws of the short-tailed dwarf hamsters are short and wide. The fifth toe of the hind paw is not shortened, and only slightly shorter than the fourth. The first toe of the front paw has a blunt nail on the remaining toes are clawed. This is in contrast to those of other hamsters at least in winter more than half as long as the respective toes. The soles of the front and rear paws are covered with dense hair up to the claws. The pads are smaller and not visible because of the dense pubescence.

The fur of the short-tailed dwarf hamster is top, gray to brown yellow and white hand. On the sides of the body the coat the bottom consists of three arches upwards. The sides of the nose, upper lip, the lower part of cheeks and flanks, limbs, tail and belly are white. The Djungarian hamster have a dark dorsal stripe. A dark spot on the chest is not available. In contrast to other hamsters, the anterior wall of the cheek pouch is hairy. These are great, and the females have eight teats.

The facial skeleton of the short-tailed dwarf hamster is comparatively short. The zygomatic arches are far apart, in the front section more than in the rear, and be steep apart. The original surface of the masseter muscle on the upper jaw is well defined, covers the sub- hole eyes and goes further than other hamsters up and back to the front portion of the zygomatic arch.

Particularly in the area of the cranial base of the skull is high and the brain capsule is relatively high and extended. Bone strips between the frontal bone and the parietal bones are absent. The wings of the sphenoid bone pits are recessed wide and slightly U-shaped. The construction of the bullae similar to the mouse hamster. They are small with tubular extension front ends.

The lower jaw of the short-tailed dwarf hamster is characteristic of hamsters. The notch on the branches is deep and the appendages, especially the muscle extension and the extension angle are long. The structure carrying the alveoli bone protuberance is relatively weakly developed and is before the middle of the muscle extension. The body of the mandible is relatively short and steep curved than other hamsters.

Teeth

The cusps of the upper molars are opposed. Even if they are slightly offset from each other, the furrows are closed between. Only the furrow between the central cusp of the first molar tooth pair can be open to the front and inside. At the lower molars, the protuberances being mutually offset. However, closed grooves are still present, even the. Between the central cusp of the first molar tooth pair and between the front pair of cusps of the second molar tooth The anterior cusp of the first upper molar are relatively large and of equal length. Compared to the following pair of cusps are noticeably narrower arranged and clearly shifted to the outside. The anterior cusp of the first bottom molar on the other hand more clearly separated from each other and the outer one is significantly larger than the inner.

The inner " neck " of the second and third upper molar tooth tend to decrease, and in particular that of the third molar, while the external are marked. The length of the upper third molar equivalent to about half the length of the second upper molar tooth. Mostly it is something more. The length of the third lower molar equivalent to about two thirds of the length of the lower second molar tooth.

Body skeleton

The hip bone of the short-tailed dwarf hamster is. , As in the mouse hamsters relatively short with short iliac and weakly pronounced iliac cusp The femur is short and only slightly longer than the mouse hamsters. His neck is shortened, so that the head appears more than other hamsters chair shaped. The fitting on the shin part of the fibula is comparatively long. The humerus is not shortened. The cubit is long with a relatively short elbow extension and a relatively flat and wide groove along the outer surface.

Cytogenetics

According Romanenko and colleagues ( 2007) adopted the original karyotype of the short-tailed dwarf hamster with 40 chromosomes differs by 11 chromosome 15 chromosome splits and mergers from the assumed original karyotype of the mouse -like.

The karyotype of Roborowski dwarf hamster differs according to Schmid and colleagues ( 1986) and Haaf et al (1987 ) by seven or eight independent centric fusions, inversions, a possible telomeric fusion, the amount of constitutive heterochromatin and its DNA base pair composition the karyotype of the Djungarian hamster.

Way of life

The short-tailed dwarf hamster feed mainly on the seeds of plants such as the hair - esparto, Salpeterkräutern, quilting alyssum and pea shrubs. Most active they are in the evening and early morning, but they are somewhat active during the night. In contrast to other hamsters, they exhibit a relatively large tolerance towards conspecifics and both parents can be involved in the rearing of young animals.

Distribution and phylogeny

The distribution of short-tailed dwarf hamsters are the mountainous and flat forests, steppes and semi-deserts of Mongolia, in adjacent areas of China, to the east and northeast Kazakhstan, south of the West Siberian lowlands, in Tuva and in Daurien.

Fossils are known from the Pleistocene of Europe, the Middle Pleistocene and / or the Upper Pleistocene of Asia and the Holocene Asia. Schaub (1930 ) classified some as Cricetulus to certain altpleistozäne fossils from caves Somerset in the UK and other parts of Europe, the short-tailed dwarf hamsters. According to Gromov and Jerbajewa ( 1995) finds in upper pleistocene layers of Irtyschgebiets credible, the allocation of finds this time west to Europe, however, is based on erroneous determinations.

According to molecular genetic studies, the short-tailed dwarf hamster split already at the end of the Miocene. Your assigned fossils therefore missing for the entire Pliocene. The lack of fossils prevents the determination of an ecological or geographical event that led to the elimination of the short-tailed dwarf hamster. The kinship with other fossil hamsters are also not clear.

System

Outer systematics

The short-tailed dwarf hamsters are probably basal to the middle hamsters and the hamsters Cricetus the group. This is the result of molecular genetic studies of the mitochondrial cytochrome b and 12S rRNA genes and the nuclear vWF gene come by Neumann and co-workers (2006). Measurements by means of a constant molecular clock result in a spin-off in front of 8.5 to 9 million years ago, and by means of a relaxed molecular clock secession against 12.2 million years. According to studies of the 12S rRNA gene by Lebedev and co-workers ( 2003), the Tibetan Dwarf Hamster may be their sister group.

Studies of the nuclear GHR, BRCA1, RAG1 and c -myc genes by Steppan and colleagues ( 2004) confirm the basal position of the short-tailed dwarf hamster and result in a spin-off from 13.5 to 14.1 million years ago when viewed from all four genes and a spin-off of 12.4 million years ago when considering only the GHR gene. Cytogenetic studies using G- banding by Romanenko et al (2007) also confirm the basal position.

According to studies of the nuclear IRBP gene by Jansa and Weksler ( 2004), the short-tailed dwarf hamsters are, however, possibly a sister group of the middle hamster. The same result studies of nuclear LCAT and vWF genes by Michaux et al ( 2001).

Inside systematics

Musser and Carleton (2005) distinguish three types of short-tailed dwarf hamster:

• The Roborowski dwarf hamster ( Phodopus roborovskii ) in Mongolia, in adjacent areas of China, in Tuva and eastern Kazakhstan and
• The two types of Djungarian hamsters ( Phodopus sungorus Group) of the Campbell's dwarf hamster ( Phodopus ) in Mongolia, China and adjacent areas in Daurien and
• The Djungarian hamster ( Phodopus sungorus ) in northeastern Kazakhstan and south of the West Siberian Lowland.

In many classifications, the Djungarian hamster are combined in a way. From Roborowski dwarf hamster they are more different than other recognized genera of hamsters with each other. According to Neumann and employees, the genetic distance is measured by the cytochrome b gene of 18.4 percent, as measured by the 12S rRNA gene and 5.2 percent as measured by the vWF gene 4.6 percent. Measurements by means of a constant molecular clock give a splitting million before 4.9 to 5.2 years and using a relaxed molecular clock splitting before 6.9 million years. Morphological and cytogenetic differences are also large and Neumann and co-workers propose to provide the Djungarian hamster in the separate genus Cricetiscus.

Designation and relevance to humans

Gerrit Smith Miller presented to the genus Phodopus 1910 and certain Cricetulus bedfordiae, a subspecies of Roborowski dwarf hamster, as type species. The genus name is derived from ancient Greek phodos ( φωδος, genitive of phos φως " burn " ) and pous ( πους "foot" ) and refers to the large, verschmolzenenen bales on the soles of the Roborowski dwarf hamster. As a German common names are " short-tailed dwarf hamster " (Flint, 1966; Piechocki, 1969) and " short-tailed dwarf hamster " ( Niethammer, 1988 ) was used.

Short-tailed dwarf hamsters can occur on cereal area as pests, but their numbers are everywhere so low that the damage is insignificant. They are natural hosts of the pathogen of some infectious diseases to humans. All species are kept as a pet.