LAUSR

Reproductive hormones in serum concentrations of progesterone, estradiol and testosterone in female Indo-Pacific bottlenose dolphins (Tursiops aduncus, n = 12) housed in Ocean Park Hong Kong were investigated in the present study. Results showed that, onset of puberty of captive Indo-Pacific bottlenose dolphins was at 5 y while sexual maturity is at six. Average serum progesterone concentrations in non-pregnant sexually mature individuals was 0.33(0.25-0.97) ng/mL (interquartile), significantly higher than in immature ones 0.26(0.25-0.38) ng/mL. This study found significant difference in serum estradiol concentrations between individuals at the onset of puberty (9.5±1.7 pg/mL, ±SD) and not (below detection limit 9 pg/mL). A slightly seasonal breeding pattern, with progesterone values tend to be higher from February to October (0.38[0.25-1.07] ng/mL) was inferred. During pregnancy, serum progesterone concentrations range from 10.54±8.74 ng/mL (indexed month post-conception [IMPC] 0) to 25.49±12.06 ng/mL (IMPC 2), and display a bimodal pattern with two peaks in early- (25.49±12.06 ng/mL, IMPC 2) and late-pregnancy (21.71±10.25 ng/mL, IMPC 12) respectively. Serum estradiol concentrations can seldom be detected in early-pregnancy and increase constantly in mid- (9.45±1.83 pg/mL) and late-pregnancy (11.88±3.81 pg/mL), with a spike (15.45±6.78 pg/mL) one month prior to delivery. Serum testosterone concentrations elevate significantly in IMPC 7 (0.36±0.10 ng/mL) compared to other months (0.16±0.10 ng/mL) of the year. The present study provides normal concentration profiles for some reproductive hormones in female Indo-Pacific bottlenose dolphins; and can contribute to the breeding monitoring of this species. Also, our study would shed further light on the reproductive physiology of small cetaceans. This article is protected by copyright. All rights reserved.