Endocrine Control of Embryonic Diapause in the Australian Sharpnose Shark Rhizoprionodon taylori

WALTRICK, D.; JONES, S.M.; SIMPFENDORFER, C.; AWRUCH C. A.

PLOS ONE

PUBLIC LIBRARY SCIENCE

Lugar: San Francisco; Año: 2014

1932-6203

The reproductive cycle of the Australian sharpnose shark, Rhizoprionodon taylori, includes a temporary suspension ofdevelopment at the commencement of embryogenesis termed embryonic diapause. This study investigated levels of 17bestradiol(E2), testosterone (T) and progesterone (P4) in plasma samples of mature wild female R. taylori capturedthroughout the reproductive cycle and correlated them with internal morphological changes. Levels of T were elevatedthrough 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 ofandrogens in the termination of embryonic diapause. As in other elasmobranchs, a concomitant increase of E2 with ovarianfollicle size indicated a direct role of this hormone in regulating vitellogenesis, while a peak in P4 suggested this hormone isassociated with preovulation and ovulation. Additionally, significant correlations between photoperiod or watertemperature and maximum follicular diameter and hepatosomatic index suggest that these abiotic factors may also playa role triggering and regulating the synchrony and timing of reproductive events.