Sattler Renae, Polasek Lori
Alaska Sea Life Center, Seward, Alaska.
Institute of Marine Science, School of Fisheries and Ocean Sciences, University of Alaska Fairbanks, Fairbanks, Alaska.
Zoo Biol. 2017 Sep;36(5):323-331. doi: 10.1002/zoo.21381. Epub 2017 Sep 13.
While the proximate driver behind the decline of the Western stock of Steller sea lions (Eumetopias jubatus, >80% since 1970s) is likely multifactorial, the population reduction may have been powered by a decrease in fecundity. A harvest of Steller sea lions in the 1970s and 80s revealed a 30% reduction in the proportion of pregnant females from early (October-November) to late gestation (April-May). Identification and quantification of these reproductive failures are difficult when we lack species-specific data on endocrinology associated with discrete stages of the reproductive cycle (i.e., estrus, implantation, and gestation). We tracked changes in serum estradiol and progesterone in three adult female Steller sea lions from 2011 to 2015. In all years and most females, a discrete increase in estradiol was observed during the breeding season (June-August), indicative of estrus. Estradiol concentrations from October to May in a pregnant female compared to her corresponding values when non-pregnant did not consistently differ through gestation. An elevation in progesterone was observed in all females and all years beginning approximately in June and lasting through November. This likely results from progesterone production by the corpus luteum in both pregnant and pseudopregnant females. Serum progesterone shows promise as a diagnostic tool to identify pregnancy during months 3-5 (December-February) of the 8-month active gestation following embryonic implantation. This study provides ranges of key hormones during estrus, embryonic diapause/pseudopregnancy, and gestation in pregnant and non-pregnant females for studying reproduction in Steller sea lions.
虽然西太平洋海狗（北海狗，Eumetopias jubatus，自20世纪70年代以来数量减少超过80%）数量下降的直接驱动因素可能是多方面的，但种群数量减少可能是由繁殖力下降导致的。20世纪70年代和80年代对北海狗的捕获显示，怀孕雌性的比例从妊娠早期（10月至11月）到晚期（4月至5月）下降了30%。当我们缺乏与生殖周期离散阶段（即发情期、着床期和妊娠期）相关的特定物种内分泌学数据时，识别和量化这些生殖失败是困难的。我们追踪了2011年至2015年三只成年雌性北海狗血清雌二醇和孕酮的变化。在所有年份以及大多数雌性中，在繁殖季节（6月至8月）观察到雌二醇有明显增加，表明处于发情期。与非怀孕时相应值相比，怀孕雌性在10月至5月期间的雌二醇浓度在整个妊娠期并非始终存在差异。在所有雌性和所有年份中，大约从6月开始到11月持续观察到孕酮升高。这可能是由于怀孕和假孕雌性黄体产生孕酮所致。血清孕酮有望作为一种诊断工具，用于识别胚胎着床后8个月活跃妊娠期的第3至5个月（12月至2月）的怀孕情况。本研究提供了发情期、胚胎滞育/假孕以及怀孕和未怀孕雌性妊娠期关键激素的范围，用于研究北海狗的繁殖情况。
