Beery Annaliese K, Trumbull Justin J, Tsao Jyeming M, Costantini Ruth M, Zucker Irving
Helen Wills Neuroscience Institute, University of California, 132 Barker Hall, MC 3190, Berkeley, CA 94720, USA.
Proc Biol Sci. 2007 Jan 22;274(1607):281-6. doi: 10.1098/rspb.2006.3726.
Day length is the primary cue used by many mammals to restrict reproduction to favourable spring and summer months, but it is unknown for any mammal whether the seasonal loss of fertility begins at the same time and occurs at the same rate in females and males; nor it established whether the termination of mating behaviour in males and females coincides with the loss of fertility. We speculated that females, owing to their greater energetic investment in reproduction, are the limiting sex in terminating offspring production in short days (SDs). Oestrous cycles and production of young were monitored in Syrian hamsters (Mesocricetus auratus) transferred from long days (LDs) to SDs. Females were mated to LD males after three to eight weeks of SD treatment; in a parallel experiment, males housed in SDs were mated to LD females. After five and eight weeks in SDs, at least twice as many males as females were fertile. Both males and females continued to copulate for several weeks after becoming infertile. The onset of seasonal infertility occurs earlier in females than males and the decline in fertility precedes the seasonal loss of mating behaviour in both sexes.
日照时长是许多哺乳动物用来将繁殖限制在适宜的春季和夏季月份的主要线索，但对于任何一种哺乳动物来说，尚不清楚生育能力的季节性丧失在雌性和雄性中是否同时开始且以相同的速率发生；也不确定雄性和雌性的交配行为终止是否与生育能力的丧失同时发生。我们推测，由于雌性在繁殖过程中投入了更多的能量，因此在短日照（SD）条件下，雌性是限制后代生产终止的性别。对从长日照（LD）转移到短日照的叙利亚仓鼠（金仓鼠）的发情周期和幼崽生产情况进行了监测。在短日照处理三到八周后，将雌性与长日照雄性交配；在一项平行实验中，将饲养在短日照条件下的雄性与长日照雌性交配。在短日照环境中五周和八周后，可育雄性的数量至少是雌性的两倍。雄性和雌性在失去生育能力后仍继续交配数周。季节性不育在雌性中比在雄性中出现得更早，并且生育能力的下降在两性季节性交配行为丧失之前就已发生。
