RUSSIAN HAMSTER
The Russian hamster (Phodopus sungorus) has footpads covered in fur, hence the common name “hairy footed hamster” (Fig. 11.13). Adult males are about 11 cm long and have a body weight of 40-50 g; the females are smaller, being 9 cm long and about 30 g (Cantrell & Padovan 1987).
The dorsal fur is gray, with a dark brown stripe down the middle from the nape to the tail base; ventrally the fur is white. The female has four pairs of mammary glands. As well as the flank glands they have a ventral sebaceous gland that is larger in males than females (Cantrell & Padovan 1987; Harkness & Wagner 1995).The pelage will change to a white coat when exposed to natural light cycles and colder temperatures, an ability that evolved in order to provide camouflage in the snow (Cantrell & Padovan 1987). Under the influence of the pineal gland, increased melatonin production inhibits prolactin and causes the new fur to grow unpigmented as winter white. These hamsters do not hibernate but, if the temperature drops to 19° C for a few days, there is a decrease in body weight and the hamster goes into torpor for 4-8 hours each day in order to conserve energy (Cantrell & Padovan 1987).
This hamster is commonly used in laboratory research for studies in photoperiodism and the pineal gland. The male exhibits large testicles, enlarged accessory glands, and greater body weight when exposed to light for more than 13 hours per day (Cantrell & Padovan 1987).