Steinlechner St, Heldmaier G, Becker H
Department of Biology, Philipps-University, D-3550, Marburg, Germany.
Oecologia. 1983 Dec;60(3):401-405. doi: 10.1007/BF00376859.
Photoperiod is the primary environmental cue for seasonality in the Djungarian hamster (Phodopus sungorus). This species reduces its body weight by 30% during winter to reduce its energy requirements. The aim of this study was (1) to examine the influence of food intake on the body weight cycle and (2) to evaluate the role of photoperiod and melatonin in determining this seasonal cycle.While body weight increased slightly (7%) from August through December in long photoperiod, it dropped significantly (32%) in the natural photoperiod group and food intake gradually decreased in this group by about 20%. After two periods of 40% food restriction, the hamsters in long photoperiod rapidly returned to their initial body weight. In contrast, hamsters under natural photoperiod only gained weight until they had reached the body weight of the controls at that particular time.In a second experiment, hamsters were kept under natural photoperiod throughout the year. At 6 different intervals two groups of hamsters were implanted with melatonin capsules and transferred to either short (LD 8:16) or long photoperiod (LD 16:8). The results show that the seasonal change in body weight is caused by a combined action of photoperiod and a change in the animals' sensitivity towards photoperiod and melatonin.
光周期是黑线毛足鼠季节性变化的主要环境线索。该物种在冬季体重会降低30%，以减少能量需求。本研究的目的是：（1）研究食物摄入量对体重周期的影响；（2）评估光周期和褪黑素在决定这一季节性周期中的作用。在长光周期条件下，体重从8月到12月略有增加（7%），而在自然光照周期组中体重显著下降（32%），且该组的食物摄入量逐渐减少约20%。经过两个阶段40%的食物限制后，长光周期条件下的仓鼠迅速恢复到初始体重。相比之下，自然光照周期下的仓鼠体重仅增加，直到达到该特定时间对照组的体重。在第二个实验中，仓鼠全年处于自然光照周期。在6个不同时间段，两组仓鼠被植入褪黑素胶囊，然后转移到短光周期（LD 8:16）或长光周期（LD 16:8）环境中。结果表明，体重的季节性变化是由光周期以及动物对光周期和褪黑素敏感性变化的共同作用引起的。
