Seasonal Biorhythms in Captive Voles Microtus rossiaemeridionalis Ognev, 1924

Abstract

In studying ecological features of individual species, it is important to use experimental models of the processes that take place in natural populations. Seasonal rhythms can be manifested to various degrees and differ even in closely related species (Cheprakov, 2002). We studied seasonal changes in body weight, exterior characters, and the frequency of chromosome aberrations in captive Microtus rossiaemeridionalis voles ( 2 n = 54) under conditions of a photoperiod close to the natural photoperiod at temperate latitudes and smoothed seasonal fluctuations in temperature. The study period was divided into the following seasons: January 16‐April 15, April 16‐July 15, July 16‐October 15, and October 16‐January 15. We observed changes in body weight by season in different age groups. At the age of one month, the greatest body weight was recorded in animals born from July to October, and the smallest body weight in animals born from October to April (differences are significant when compared to other seasons taken together, p < 0.05). The voles born from April to July outweighed all other voles by the age of three months ( p < 0.01) and grew to their definitive body size by the age of five months, whereas other voles had a lower body weight at this age ( p = 0.05) and continued growing until the age of seven months. Beginning from this age, animals born in different seasons did not differ in body weight. The absolute values of this parameter depended on the period when it was determined: from mid-spring to midsummer, the body weight of adult animals was greater than in other seasons ( p < 0.01). At the age of one month, the greatest body lengths (as well as weight) were observed in the voles born from mid-July to mid-October ( p < 0.05). Voles born from April to July at the age of three to five months were larger than the remaining voles ( p < 0.01) and reached their definite size at the age of five months. At the age of seven months and older, animals born and collected in different seasons did not differ in body length.