Centre for Research in Animal Behaviour, University of Exeter, Exeter, EX4 4QG, UK.
Department of Biology, University of York, York, YO10 5DD, UK.
Sci Rep. 2018 Aug 27;8(1):12833. doi: 10.1038/s41598-018-31047-8.
In most species the reproductive system ages at the same rate as somatic tissue and individuals continue reproducing until death. However, females of three species - humans, killer whales and short-finned pilot whales - have been shown to display a markedly increased rate of reproductive senescence relative to somatic ageing. In these species, a significant proportion of females live beyond their reproductive lifespan: they have a post-reproductive lifespan. Research into this puzzling life-history strategy is hindered by the difficulties of quantifying the rate of reproductive senescence in wild populations. Here we present a method for measuring the relative rate of reproductive senescence in toothed whales using published physiological data. Of the sixteen species for which data are available (which does not include killer whales), we find that three have a significant post-reproductive lifespan: short-finned pilot whales, beluga whales and narwhals. Phylogenetic reconstruction suggests that female post-reproductive lifespans have evolved several times independently in toothed whales. Our study is the first evidence of a significant post-reproductive lifespan in beluga whales and narwhals which, when taken together with the evidence for post-reproductive lifespan in killer whales, doubles the number of non-human mammals known to exhibit post-reproductive lifespans in the wild.
在大多数物种中，生殖系统与体细胞以相同的速度衰老，个体在死亡前会持续繁殖。然而，有三种物种的雌性——人类、虎鲸和短鳍领航鲸——相对于体细胞衰老，其生殖衰老的速度明显加快。在这些物种中，相当一部分雌性在其生殖寿命结束后仍能继续生存：它们有一个生殖后寿命。由于难以量化野生种群中生殖衰老的速度，对这种令人费解的生活史策略的研究受到了阻碍。在这里，我们提出了一种使用已发表的生理数据来衡量齿鲸生殖衰老相对速度的方法。在十六种有可用数据的物种中（不包括虎鲸），我们发现有三种具有显著的生殖后寿命：短鳍领航鲸、白鲸和独角鲸。系统发育重建表明，雌性生殖后寿命在齿鲸中已经独立进化了多次。我们的研究首次证明了白鲸和独角鲸存在显著的生殖后寿命，加上虎鲸存在生殖后寿命的证据，这使已知在野外具有生殖后寿命的非人类哺乳动物数量增加了一倍。
