N. Yu. Feoktistova

Intraspecific organization of dwarf hamsters Phodopus campbelli and Phodopus sungorus (Rodentia: Cricetinae) basing on mtDNA analysis.

35 Two dwarf hamster species of the genus Phodopus —Djungarian hamster ( Ph. sungorus ) and Campbell’ hamster (Ph. campbelli )—have been widely used since 1960s in many laboratories of the world as model objects for studying various aspects of physiology, behavior, and seasonal changes in the organism. We were the first to perform analysis of mitochondrial DNA polymorphism of these two species, which revealed different phylogenetic lines separated by significant genetic distances. This finding is indicative of a long-term isolated existence of groups of hamster populations in different parts of their range and their independent evolution. This fact should be taken into account in interpreting the results of laboratory experiments and field observations. The sample of Campbell’ hamsters consisted of 24 animals from 13 geographic sites encompassing the major part of their range: Chuya and Kurai steppes (Russia), western and central areas of Mongolia, Inner Mongolia (China), and Chita region (Russia). We also analyzed the nucleotide sequences of hamsters from the vivarium of the Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences. The sample of Djungarian hamsters consisted of 18 animals, nine of which were caught in three sites of the main part of their range (Northern and Eastern Kazakhstan and Novosibirsk region (Russia)), and nine were caught in an isolated part of the range in the Minusink Basin (Russia). In addition, we analyzed the nucleotide sequences of mtDNA of Djungarian hamsters from vivariums of the Severtsov Institute of Ecology and Evolution (Russian Academy of Sciences) and the Institute of Animal Breeding and Husbandry (MartinLuther-University, Halle, Germany).

[Seasonal changes of steroid levels in blood plasma of three Phodopus species (Mammalia, Cricetinae)].

Seasonal change of the base plasma level of testosterone and cortisol in males and progesterone, estradiol, and cortisol levels in females were analyzed in three Phodopus species: Ph. campbelli (Campbell’s hamster), Ph. sungorus (Djungarian hamster), and Ph. roborovskii (Roborovskii dwarf hamster). Our results showed a significant difference in the seasonal plasma level of testosterone and cortisol in males and cortisol in females of all Phodopus species, though the rhythms of breeding activity were similar. The results are discussed in the context of adaptive differences between hormonal patterns of more evolutionarily modern species (Campbell’s hamster and Djungarian hamster) and the more evolutionarily old Roborovskii dwarf hamster, the phylogenic position of which is currently under discussion.

Ecological and physiological characteristics of seasonal biology of the mongolian hamster, Allocricetulus curtatus allan 1940 (Cricetinae, Rodentia)

Analysis of the seasonal dynamics of body weight and steroid hormones (cortisol, progesterone, and testosterone), the pattern of hypothermia, and basic reproductive parameters has been performed in the Mongolian hamster (Allocricetulus curtatus), a poorly studied rodent species inhabiting areas with a sharply continental climate. The results show that torpor bouts take place in wintering animals. Changes in body weight during the autumn-winter season are insignificant. The pattern of fluctuations in the levels of sex steroids and cortisol is similar to that in dwarf hamsters of the genus Phodopus. Seasonal features in the dynamics of basal cortisol level differentiate A. curtatus from the closely related Eversmann’s hamster (A. eversmanni), which may be due to differences in the social structure of these species.

Hormonal Response to Conspecific Chemical Signals As an Indicator of Seasonal Reproduction Dynamics in the Desert Hamster, Phodopus roborovskii

Changes in male blood plasma testosterone and cortisol in response to exposure to scent marks (urine and midventral gland secretion, MVGS) of conspecific males and diestrous females in different seasons have been studied in the desert hamster (Phodopus roborovskii), a species whose ecological features are poorly known. The results show that a significant increase in the plasma testosterone level is observed in winter (only to female MVGS), spring (to female MVGS and urine), and summer (to female urine), but not in autumn. The level of plasma cortisol significantly increases only in response to female urine in spring and male MVGS in summer.

Genetic structure of urban population of the common hamster (Cricetus cricetus)

Over the past half-century, the common hamster (Cricetus cricetus), along with range-wide decline of natural populations, has actively populated the cities. The study of the genetic structure of urban populations of common hamster may shed light on features of the habitation of this species in urban landscapes. This article is focused on the genetic structure of common hamster populations in Simferopol (Crimea), one of the largest known urban populations of this species. On the basis of the analysis of nucleotide sequences of the cytochrome b gene and mtDNA control region, and the allelic composition of ten microsatellite loci of nDNA, we revealed that, despite the fact that some individuals can move throughout the city at considerable distances, the entire population of the city is represented by separate demes confined to different areas. These demes are characterized by a high degree of the genetic isolation and reduced genetic diversity compared to that found for the city as a whole.

Daily torpor in hamsters (Rodentia, Cricetinae)

Study of ecological adaptations, including torpor, related to survival through the adverse conditions of the autumn-winter season is important for both the estimation of the body reserves in mammals in general and the search for the ways to increase the cold-stress resistance in humans. The changes in the body temperature during the period from October to May were studied in hamsters of six species under the natural photoperiod and temperature conditions. Incidental winter torpor (a drastically decreased physiological activity) was detected in all species except Cricetulus griseus; in three of them, it had not been observed before. No specific combination of conditions causing torpor was identified. Apparently, it is determined by individual characteristics of the animal. Torpors were the most frequent in January, at temperatures from −15 to −5°C; their depth was positively correlated with the ambient temperature. Since torpor is a rare event, it is assumed to be a stored resource of the body allowing animal to save energy and occurring only in extreme situations.

A record of hibernation on the surface of incisor teeth in the hamster Mesocricetus raddei (Nehring, 1894)

The surface of the lower incisor teeth was studied in an adult male Mesocricetus raddei hamster with a temperature logger implanted into its peritoneal cavity in June 2010. From July 2010 to March 2011, the hamster lived under natural conditions in an enclosure and overwintered in a self-made burrow. Logger data showed that, beginning from mid-August, the animal body temperature periodically dropped and then returned to the norm, with the duration and depth of hypothermia (torpor bouts) increasing and those of nor-mothermia (arousals) decreasing with time. Growth increments on the incisor surface (presumably, daily increments) were unclear in the apical and middle tooth parts but very distinct in the basal part. The number and width of basal increments generally corresponded to the number and duration of arousals. The growth of the incisors apparently continued throughout the winter season, with every arousal after a torpor bout being marked by the formation of a distinct increment on the incisor surface. Thus, it appears that the pattern of increments on the incisor surface can be used to evaluate the course of wintering in hibernating hamsters. Experiments with vital markers are needed to confirm this assumption.

Comparative analysis of the effect of predator odor on morphological and physiological parameters of adult male Campbell hamsters (Phodopus campbelli) and dwarf hamsters (Phodopus sungorus)

The effect of long-term exposure to natural excretions of the European polecat on the morphological parameters and hormonal status of adult male Campbell hamsters (Phodopus campbelli) and dwarf hamsters (Ph. sungorus) was studied. Exposure to volatile components of natural excreta of a potential predator did not have any significant effect on hamsters. The combined influence of volatile and nonvolatile components of the polecat’s excretions caused physiological stress in Ph. campbelli, while in Ph. sungorus, on the contrary, an increase in thymus weight and the plasma testosterone level was recorded.

Synurbization of the common hamster ( Cricetus cricetus L., 1758)

The common hamster (Cricetus cricetus L., 1758) historically formed an extensive range covering much of Europe and Asia. However, in the last 50 years almost throughout the whole range, its number in natural habitats and agrocenoses dropped sharply. At the same time, the common hamster began to settle cities, which could be considered as a biological invasion. Now urban populations are found in Vienna (Austria) and several cities of Germany, the Czech Republic, Slovakia, Poland, and Russia. By example of Simferopol, where the largest urban population exists, we show what resources the species can use in the city and what changes in the ecology and behavior follow this. It is suggested that the major factors promoting the settling of cities by the common hamster are additional environmental resources associated with the specifics of the urban environment: the emergence of new shelters, food sources, etc. We assume that ecological opportunism, polyphagy, and high stress resistance could be crucial for the ability to settle urban environments.

Decorative forms of hamsters of the genus Phodopus (Mammalia, Cricetinae): Analysis of genetic lines distribution and features of hair changes

Using a molecular genetic marker (combined sequences of the cytochrome b gene and mtDNA control region), the maternal species of the genus Phodopus were identified, which served as the starting material for the creation of artificial populations of these domesticated species, including their colored forms, in many countries around the world. The animals were purchased at pet stores in Europe, Southeast Asia, and North America and included 9 Ph. campbelli specimen (seven haplotypes), 17 Ph. sungorus animals (six haplotypes), and 5 Ph. roborovskii (one haplotype). The mtDNA sequences obtained were compared with 63 haplotypes of Ph. campbelli, 26 of Ph. sungorus, and 26 of Ph. roborovskii, which are known in natural populations. It is shown that all colored Ph. campbelli were obtained from breeding wild animals of the Western haplogroup. Haplotypes of hamsters from different areas of Tuva are closest to haplotypes of colored animals. The colored Ph. sungorus are divided into two groups. The animals that were obtained from the specimen of the isolate in the Minusinsk Basin are kept in Moscow and St. Petersburg. The animals that originate from the ancestors of the Karasuk District of the Novosibirsk Oblast are kept in the countries of Europe and South East Asia. The colored Ph. roborovskii are the descendants of the animals from the Zaisan Basin, and their haplotypes match the haplotype of one of the animals that we caught in the wild. The colored hamsters, unlike hamsters with natural color, have a disturbed normal state of hair. This is evidenced by its dimness, shagginess, and felt character, as well as the changing the ratio between the different categories of hair and their size characteristics, the deformation of the shaft until bending at the right angle and splitting of the upper parts, the cracking of the cuticle, the changing configuration and location of the medulla, and the uneven development of the cortex. It is assumed that these destructive changes are associated with the genetic characteristics of the colored forms.