Characterization and Longitudinal Monitoring of Serum Androgens, Cortisol and Corticosterone During Normal Pregnancy in the Killer Whale (Orcinus orca)
SeaWorld and Busch Gardens Reproductive Research Center, SeaWorld Parks and Entertainment Inc., San Diego, CA, USA
The secretory patterns of testosterone (T), androstenedione (A), dehydroepiandrosterone (D), cortisol (C), and corticosterone (Co) were characterized throughout 28 normal pregnancies until two-month post-partum in eleven killer whales. Effects of fetal sex, dam parity or age, and season were evaluated across either day post-conception (DPC), stage of pregnancy (pre, early, mid, late, post) or indexed month post-conception (IMPC) using a mixed model linear regression with animal ID and pregnancy as the random variables. Across DPC, T, A, and D were affected (p < 0.05) by season, with highest concentrations during spring (D, A, & T) and summer (A) as compared to the fall. A significant effect of parity on androgen production was observed only for D, with multiparous females having higher (p = 0.01) concentrations than nulliparous females. All three androgens significantly increased during each stage and IMPC with peak concentrations occurring during IMPC 10 (D), 13 (A) and 14 (T), respectively. Cortisol was affected by season (p = 0.03) with highest concentrations being detected during the months of fall, while Co was only affected by parity (p = 0.003) with significant increases observed for primiparous females as compared to nulliparous females. Cortisol and Co concentrations peaked (p < 0.05) during IMPC 17 (i.e., the month prior to parturition). The C to Co ratio during pregnancy was 8 to 1, indicating that cortisol is the major stress hormone studied to date in pregnant killer whales. The significant increase in concentrations of maternal androgens throughout pregnancy, which were unrelated to fetal sex, indicates that they play an important role during killer whale fetal development.
The authors thank the curatorial, training and veterinary staff at SeaWorld San Diego, San Antonio and Orlando for blood sample collection and processing, and the SeaWorld and Busch Gardens Reproductive Research Center staffs and intern students for sample collation and hormone assays. The authors are also grateful to Mr. Brad Andrews of SeaWorld Parks and Entertainment (SEA) for continued support of this research.
* Presenting author