Seasonal variations in the food consumption of woodchucks (Marmota monax).
Food consumption of 155 woodchucks ( Marmota monax ) was measured immediately after capture to determine whether a seasonal rhythm obtained in feeding of a natural population. Food intake of adults was lowest in March. It reached a maximum in May, then declined through the summer; some individuals increased food intake temporarily in late autumn. Comparative ata from a laboratory colony showed that a similar rhythm occurred under conditions of constant temperature and photoperiod. Variability in food consumption axima associated with different age groups, considered in the context of vailable life history information, suggested that the rhythm had a period omewhat less than 1 year.
Alteration of growth, advancement of puberty, and season-appropriate circannual breeding during 28 months of photoperiod reversal in woodchucks (Marmota monax).
In woodchucks (Marmota monax), as in other marmotine rodents, endogenous circannual metabolic and reproductive cycles persist and free-run at intervals of 10-12 mo for up to 4 yr in a neutral photoperiod of 12L:12D. The annual metabolic cycle is not altered by exposure to constant long days or short days for several months. In the wild, changes in food intake cause body weight to peak in late summer and reach nadirs in early spring, and there is a single annual breeding season in late winter. To determine whether normal changes in photoperiod entrain the endogenous circannual cycle, aspects of reproduction, food intake, and body weight were studied for 28 mo in eight groups of woodchucks housed in light-controlled rooms. These included four groups of 7-10 males and four groups of 7-10 females exposed to automated and continuous daily changes in photoperiod. The imposed changes in photoperiod resembled native Northern Hemisphere (boreal) changes or Southern Hemisphere (austral) changes in photoperiod. The treatments started at the summer solstice shortly after capture as 2.5-mo-old juveniles or 14.5-mo-old yearling adults. In austral vs. boreal woodchucks, started as juveniles, annual increases in testosterone and testis descent at 5, 14, and 23 mo of study were advanced by 2, 5, and 6 mo, respectively. Annual increases in progesterone at 7, 16, and 25 mo of study were advanced by 4, 5, and 6 mo, respectively. The older woodchucks were significantly but less dramatically affected by austral photoperiod for the first 6 mo of study, and by 8-12 mo were advanced the same as the younger animals. At 16-17 and 26-27 mo of photoperiod reversal, 16 austral females had normal pregnancy rates (78%) and produced normal-sized litters (4.3 +/- 0.2) that were advanced by 5 and 6 mo, respectively, relative to those of boreal controls. Body weights in austral vs. boreal juveniles were reduced at 3-5 mo of study but not in older woodchucks. At 1 and then 2 yr of austral lighting, peaks in body weight were advanced by 4 and then 5 mo relative to boreal controls in young animals, and by 2 and then 5 mo in older animals. Between 1 and 2 yr of austral lighting in both age groups the nadirs in food intake (45 g per day) were about 16-25% of peak food intake 6-8 mo earlier, as in boreals, but advanced by 5-6 mo relative to boreals.(ABSTRACT TRUNCATED AT 400 WORDS)
Genetic Effects of Acute and Chronic Ionizing Irradiation on Pinus sylvestrisL. Inhabiting the Chernobyl Meltdown Area
The main results of the 12-year radiation-genetic monitoring of radiobiological, cytogenetic, and genetic parameters in Pinus sylvestrisforest plantation from the Chernobyl meltdown area are presented. The acute ionizing irradiation at doses > 1 Gy was shown to induce formation of morphoses and depressed growth; at doses >2 Gy, the reproductive ability of the trees declined. The radiobiological parameters showed a linear or close to linear dose-dependence relationship. The acute irradiation at a dose of 0.5 Gy induced cytogenetic and genetic effects that were significantly higher than the corresponding control values. The relationship between the cytogenetic effects and the absorbed dose was exponential. The dependence of the mutation frequency at specific loci on the absorbed dose was described by a nonlinear curve. The results of cytogenetic analysis of seedlings obtained from seeds annually collected in zones of slight, moderate, and strong damage of Pinus sylvestrisL. are presented.