Long-term monitoring of circulating progesterone and its relationship to peripheral white blood cells in female false killer whales Pseudorca crassidens.

Long-term monitoring of circulating progesterone levels in three captive female false killer whales, Pseudorca crassidens, was conducted to characterize their reproductive events and to reveal the relationship between their estrous cycles or pregnancies and peripheral white blood cell (WBC) counts. Blood samples were collected at 2-3-day intervals or on a weekly-to-monthly basis for up to 10 years, from 2006 to 2017. In two mature females (initial body lengths of 4.22 and 4.07 m), some cyclic progesterone elevations were detected during the study period; the estimated mean (± SE) estrous cycle length was 40.5 ± 0.7 days (n=12). The seasonality of ovulation, estimated from the elevation of progesterone levels, varied among individuals or years, and ovulation did not occur every year. The third female (3.26 m) showed progesterone elevations, despite irregular cycles after sexual maturity, and became pregnant. The progesterone levels during pregnancy ranged from 7.3 to 42.2 ng/ml, and the gestation period lasted for 14 months until parturition. The mean WBC counts during estrous cycles were the lowest before the progesterone levels began to increase and then gradually increased toward the luteal phase. The WBC counts were significantly higher during pregnancy than before and were particularly high in early pregnancy. To the best of our knowledge, this is the first report of the relationship between the estrous cycle or pregnancy and WBC counts in cetaceans.

Increase in serum noradrenaline concentration by short dives with bradycardia in Indo-Pacific bottlenose dolphin Tursiops aduncus.

In cetaceans, diving behavior immediately induces a change in blood circulation to favor flow to the brain and heart; this is achieved by intense vasoconstriction of the blood vessels that serve other organs. This blood circulation response is allied to a decrease in heart rate in order to optimize oxygen usage during diving. Vasoconstrictors are present in all mammals and stimulate the contraction of the smooth muscle in the walls of blood vessels. The most important of these vasoconstrictors are the hormones adrenaline (A), noradrenaline (NA), and angiotensin II (ANG II). At present, the contribution of these hormones to vasoconstriction during diving in cetaceans is unclear. To elucidate their possible roles, changes in serum levels of A, NA and ANG II were monitored together with heart rate in the Indo-Pacific bottlenose dolphin Tursiops aduncus during 90 and 180s dives. Both brief diving periods induced an increase in serum NA concentration and a decrease in heart rate; however, no changes were detected in serum levels of A or ANG II. These data indicate that NA may play a role in diving-induced vasoconstriction.