Waltrick Daniela, Jones Susan M, Simpfendorfer Colin A, Awruch Cynthia A
Centre for Sustainable Tropical Fisheries and Aquaculture & School of Earth and Environmental Sciences, James Cook University, Townsville, Australia.
School of Zoology, University of Tasmania, Hobart, Australia.
PLoS One. 2014 Jul 3;9(7):e101234. doi: 10.1371/journal.pone.0101234. eCollection 2014.
The reproductive cycle of the Australian sharpnose shark, Rhizoprionodon taylori, includes a temporary suspension of development at the commencement of embryogenesis termed embryonic diapause. This study investigated levels of 17β-estradiol (E2), testosterone (T) and progesterone (P4) in plasma samples of mature wild female R. taylori captured throughout the reproductive cycle and correlated them with internal morphological changes. Levels of T were elevated through most of the embryonic diapause period, suggesting a role of this hormone in the maintenance of this condition. Increasing plasma T concentrations from late diapause to early active development were associated with a possible role of androgens in the termination of embryonic diapause. As in other elasmobranchs, a concomitant increase of E2 with ovarian follicle size indicated a direct role of this hormone in regulating vitellogenesis, while a peak in P4 suggested this hormone is associated with preovulation and ovulation. Additionally, significant correlations between photoperiod or water temperature and maximum follicular diameter and hepatosomatic index suggest that these abiotic factors may also play a role triggering and regulating the synchrony and timing of reproductive events.
澳大利亚尖吻鲨（Rhizoprionodon taylori）的生殖周期包括在胚胎发育开始时出现的发育暂时停滞，即胚胎滞育。本研究调查了在整个生殖周期捕获的成熟野生雌性泰勒澳大利亚尖吻鲨血浆样本中17β-雌二醇（E2）、睾酮（T）和孕酮（P4）的水平，并将它们与内部形态变化相关联。在胚胎滞育的大部分时间里，T水平升高，表明这种激素在维持这种状态中发挥作用。从滞育后期到早期活跃发育阶段，血浆T浓度的增加与雄激素在胚胎滞育终止中的可能作用有关。与其他板鳃亚纲动物一样，E2随着卵巢卵泡大小的增加而增加，表明这种激素在调节卵黄发生中起直接作用，而P4的峰值表明这种激素与排卵前和排卵有关。此外，光周期或水温与最大卵泡直径和肝体指数之间的显著相关性表明，这些非生物因素也可能在触发和调节生殖事件的同步性和时间方面发挥作用。
