The taxonomy of the genus Cricetulus has been controversial. The phylogenetic relationships both within the genus and among Cricetulus lineages and other genera were examined using a set of five nuclear and two mitochondrial genes. The results demonstrate that Cricetulus in its current treatment is a polyphyletic assemblage because the subgenus Urocricetus is phylogenetically unrelated to all other Cricetulus and is a distant sister group to Phodopus. The grey hamster (C. migratorius) proved to be closer to Cricetus and Allocricetulus than to Cricetulus proper, which includes C. barabensis C. sokolovi and C. longicaudatus. Based on these results Urocricetus is elevated to the rank of a full genus and a new genus Nothocricetulus gen.nov. is described for the grey hamster.

The hamsters of the genus Phodopus (P. campbelli, P. sungorus, P. roborovskii) inhabit different ecosystems facing them with different environmental challenges. This should have behavioural and physiological consequences, manifested genetically. Therefore, the present paper compares the daily activity rhythm of the three Phodopus species under various conditions, from highly standardized laboratory to semi-natural ones. Motor activity was recorded by the mean of passive infrared sensors (PIR), running wheels (RW) and ring-shaped sensors (RSS) placed on the burrow entrances. Under standardized laboratory conditions with artificial light-dark cycles (L:D=14:10h or 18:06h), all hamsters were active almost exclusively during the dark time. The amount of general activity (PIR method) per day was not different between males and females or between species. The onset of activity (RSS) was significantly later in P. campbelli than in the two other species, the activity offset was earliest in P. roborovskii. The latter had also the shortest duration of dark-time activity. Running wheels were used mainly during the dark time (on average 97%). P. sungorus did run significantly more than the other two species. On average they realized 9000 revolutions per day (ca. 3.5 km). The rhythm stability was lowest in P. sungorus. In some hamsters of this species, the activity onset was delayed by several hours, and the activity period was strongly compressed. Also, a free-running rhythm despite the presences of a light-dark cycle or arrhythmicity was observed in those animals. Differences between the species were also found during the last weeks of life. Whereas P. campbelli and P. roborovskii revealed clear activity rhythms until the last decade, in P. sungorus the activity rhythm disappeared from the last 100 days of life. First studies under semi-natural conditions were performed at the Biological Station of the A.N. Severtsov Institute of Ecology and Evolution in Tchernogolovka. These included experiments in a laboratory though with natural lighting and temperature conditions and in outdoor enclosures. In one of them (75 m 2) artificial nest boxes were provided, in the other two (400 m 2 each) the animals could dig their own burrows. The observed activity patterns are similar to those obtained under constant, standardized conditions. Moreover, the animals did clearly respond to the changing photoperiod. The activity patterns of each species described in the present paper are rather similar under semi-natural and artificial environmental conditions. This can be taken as evidence that the obtained species-specific patterns have a genetic basis and are not caused by the different environmental conditions.

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 tempera ture during the period from October to May were studied in hamsters of six species under the natural photope riod 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 characteris tics 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.

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The populations of mykizha Parasalmo (O.) mykiss from western and eastern coasts of Kamchatka were studied by restriction analysis of a fragment of fish mitochondrial genome that included the control region and the region of the cytochrome b gene ( cytb ). The restriction patterns obtained with five enzymes ( Msp I; Tru 1I; Rsa I; Bsu RI; Dde I) were identical in all studied individuals. Sequencing of the cytb gene showed high similarity between all samples (99.6-100%). In general, the geographical group of mykiss from Kamchatka is monophyletic with low genetic divergence at the population level. Shantarian mykiss originates most likely from that native to Kamchatka. ANIMAL GENETICS