Richter M M, Barnes B M, O'Reilly K M, Fenn A M, Buck C L
Western Kentucky University, 1906 College Heights Blvd, Bowling Green, KY 42101, USA.
Institute of Arctic Biology, University of Alaska Fairbanks, Alaska 99775, United States.
Horm Behav. 2017 Mar;89:92-97. doi: 10.1016/j.yhbeh.2016.12.007. Epub 2016 Dec 13.
Free-living ground squirrel species are sexually dimorphic in hibernation phenology. The underlying causes of these differences are not yet known. Androgens, testosterone (T) in particular, inhibit hibernation. To determine the influence of endogenous androgens on annual timing of hibernation we first measured circulating levels of T and dehydroepiandrosterone (DHEA), an adrenal androgen implicated in non-mating season aggression in other species, in free-living male arctic ground squirrels (Urocitellus parryii, AGS). We also manipulated endogenous androgen levels by surgical castration, and consequently compared body temperature records from intact (n=24) and castrated (n=9) males to elucidate the influence of endogenous androgens on annual body temperature cycles. The highest T levels (0.53±0.10ng/mL) were in reproductively mature male AGS in spring; whereas, both immature males in spring and all males in late summer had T levels an order of magnitude lower (0.07±0.01 and 0.06±0.00ng/mL, respectively). DHEA levels were higher in males during the late summer compared to reproductively mature males in spring (120.6±18.9 and 35.9±2.3pg/mL, respectively). Eliminating gonadal androgens via castration resulted in males delaying euthermy by extending heterothermy significantly in spring (Apr 22 ±2.9) than reproductive males (Mar 28 ±3.9) but did not change the timing of hibernation onset (castrate: Oct 12 ±1.0 vs. intact: Oct 3 ±3.1). We conclude that while androgens play a significant role in spring hibernation phenology of males, their role in fall hibernation onset is unclear.
自由生活的地松鼠物种在冬眠物候上存在性别二态性。这些差异的根本原因尚不清楚。雄激素，尤其是睾酮（T），会抑制冬眠。为了确定内源性雄激素对冬眠年度时间的影响，我们首先测量了自由生活的雄性北极地松鼠（Urocitellus parryii，AGS）体内T和脱氢表雄酮（DHEA）的循环水平，DHEA是一种肾上腺雄激素，在其他物种的非交配季节攻击行为中起作用。我们还通过手术阉割来操纵内源性雄激素水平，随后比较了完整雄性（n = 24）和阉割雄性（n = 9）的体温记录，以阐明内源性雄激素对年度体温周期的影响。春季生殖成熟的雄性AGS的T水平最高（0.53±0.10ng/mL）；而春季未成熟的雄性和夏末所有雄性的T水平低一个数量级（分别为0.07±0.01和0.06±0.00ng/mL）。与春季生殖成熟的雄性相比，夏末雄性的DHEA水平更高（分别为120.6±18.9和35.9±2.3pg/mL）。通过阉割消除性腺雄激素导致雄性在春季显著延长异温期从而推迟了常温期（4月22日±2.9天），比生殖雄性（3月28日±3.9天）延迟，但没有改变冬眠开始的时间（阉割组：10月12日±1.0天，完整组：10月3日±3.1天）。我们得出结论，虽然雄激素在雄性春季冬眠物候中起重要作用，但其在秋季冬眠开始中的作用尚不清楚。
