Effect of Photoperiod in the Regulation of the Annual Testicular Cycle of a Subtropical Mammal,the Indian Palm Squirrel,Funambulus pennanti

编号 zgly0000125043

文献类型 期刊论文

文献题名 Effect of Photoperiod in the Regulation of the Annual Testicular Cycle of a Subtropical Mammal,the Indian Palm Squirrel,Funambulus pennanti

作者 A.B.SINGH  CHANDRAMOHINICHATURVEDI 

作者单位 DepartmentofZoology 

母体文献 Biomedical and Environmental Sciences（生物医学与环境科学：英文版） 

年卷期 1995,8(1)

页码 65-73

年份 1995 

分类号 Q958.112.3  Q492 

关键词 亚热带  哺乳动物  松鼠  印度  年度睾丸周期  季节性繁殖  性周期  调节作用  光周期 

文摘内容 In seasonally breeding subtropical mammal,the Indian palm squirrel(Funambulus pennanti),reproductive recrudescence is initiated before the winter solstice followed by sexually active condition which extends until the end of summer season.Onset of seasonal regression coincides with the annual decrease in daily photoperiod and the increased level of relative humidity resulting from the arrival of monsoon at this latitude.To test the photoperiodic responses,three groups of squirrels were exposed to natural day length(NDL),long day length(LD15:9),and short day length(LD6:18) over a period of one year beginning from March.Squirrels of all these groups were exposed to similar ambient temperature and humidity conditions.Initially,the rate of testcular development was similar in control and long day squirrels attaining peak values in May(0.67cm^3)and June(0.7cm^3)respectively.Thereafter,while the gonads of controls regressed,the latter maintained a plateau.On the other hand,the gonads of short day squirrels regressed sharply until June(0.21cm^3) followed by spontaneous recrudescence and finally a plateau(0.55cm^3).These results indicate that initially squirrels are photosensitive(as long days are gonadostimulatory and short days are inhibitory)in the first half of summer season but eventually become refractory to the inhibitory effect of short days.Obviously,an acyclic condition is developed under constant long as well short day conditions maintaining the neuroendocrine-gonadal-axis in a continuously active state.We suggest that in nature although gonadal growth of this species does not synchronice with the increase in daily conditions.Present study also indicates that this species has developed a strong photoperiodic mechanism which may surpass the reproductive effect of other environmental factors when maintained in constant conditions of day length。