黑线仓鼠自身生存和繁殖输出间的权衡不受温度影响

The trade-off between the energy allocation to maintenance and reproduction in striped hamster is independent of temperature

为阐明野生小型哺乳动物哺乳期能量收支对策,深入理解最大持续能量摄入(Sus EI)限制的因素和机理,测定了不同环境温度下(21℃、30℃和5℃)与哺育不同胎仔数(自然胎仔数Con、减少Minus和增加胎仔数Plus)的黑线仓鼠哺乳期体重、摄食量、基础代谢率(BMR)、非颤抖性产热(NST),以及褐色脂肪组织(BAT)细胞色素C氧化酶(COX)活性、血清T3、T4和催乳素水平。结果显示,哺乳期体重显著降低,摄食量显著增加,21℃和30℃组间差异不显著。最大持续摄食量约为14 g/d,Minus组分别比Con组和Plus组低20.3%和18.6%。温度对摄食量的影响显著,5℃下摄食量达16 g/d,比21℃和30℃组高14%(P<0.05)。Con组和Minus组胎仔数维持稳定,而Plus组胎仔数显著降低,断乳时Con组和Plus组胎仔数差异不显著。Minus组胎仔重显著低于Con组和Plus组。断乳时Minus组平均幼体体重比Con组和Plus组分别高17.9%和24.9%(P<0.05)。5℃下BMR、NST、COX活性、血清T3、T4和催乳素水平显著高于21℃和30℃,而21℃和30℃组间差异不显著。结果表明:黑线仓鼠Sus EI水平为5×BMR,低温下可通过增加能量摄入应对代谢产热的能量支出,在自身维持和繁殖输出之间采取了"权衡分配"的能量学策略,研究结果支持热耗散限制假说,也符合外周限制假说的预测。

The present study was aimed at examining the energy budget during lactation in small mammals,within which the factors limiting maximum sustained energy intake（Sus EI） and the physiological mechanisms underpinning the limitation would be further explored. Body mass,food intake,litter size and litter mass during lactation were determined in striped hamsters raising natural litters（Con）,minus 2-3（Minus） and plus 2-3 pups（Plus） at 21℃,30℃ and 5℃. Basal metabolic rate（BMR）,nonshivering thermogenesis（NST）,cytochrome c oxydase（COX） activity of brown adipose tissue（BAT）,serum T3,T4 and prolactin levels also were measured. Females increased food intake,but decreased body mass throughout lactation,during which the differences between 21 and 30℃ were not significant. Maximum asymptotic food intake averaged 14 g / d,and it was lower by 20. 3% and 18. 6% in Minus group than Con and Plus groups,respectively. The effect of temperature on food intake was significant. Food intake was increased to 16 g / d at 5℃,which was significantly higher than that at 21 and 30℃（by 14%,P 0. 05）. Litter size decreased significantly in Plus group,but did not change in Con and Minus groups throughout the lactation. Mean litter size was 4. 5 ± 0. 3,2. 6 ± 0. 3 and 4. 6 ± 0. 3 in Con,Minus and Plus groups,respectively,at weaning（P 0. 01）,and no difference was observed between Con and Plus groups. On weaning day,litter mass was not different between Con and Plus groups,but it was significantly lower in Minus group（33. 9 ± 3. 8） g than Con（50. 9 ± 2. 2） g and Plus groups（49. 0 ± 1. 8） g. Mean pup body mass was（13. 7 ±0. 7） g in Minus group,which was higher by 17. 9% and 24. 9% than that in Con（11. 6 ± 0. 5） g and Plus（10. 9 ± 0. 6）g groups（P 0. 05）,respectively. BMR,NST,BAT COX activity,serum T3,T4 and prolactin levels were significantly higher at 5℃ than 21℃ and 30℃,whereas no differences were observed between 21℃ and 30℃. It suggested that Sus EIwas 5 × BMR in striped hamster raising different litter size at 5℃,21℃ and 30℃. Cold-exposed hamsters were able to increase energy intake to cope with the energy expenditure for thermogenesis,showing a trade-off energetic budget between maintenance and reproductive output. The finding provided support for the＂heat dissipation limitation hypothesis＂,but was also consistent with the prediction of the ＂peripheral limitation hypothesis＂.