Seasonal changes in circulating gonadal steroid levels and physiological evidence for the presence of intrinsic circannual reproductive cycles in captive finless porpoises <i>Neophocaena asiaeorientalis</i> from the western Inland Sea, Japan

Abstract

We monitored annual fluctuations of gonadal steroid levels in three sexually mature captive finless porpoises (Neophocaena asiaeorientalis; two males and one female) from two different facilities over 56–91 months. Two animals (one male and one female) were held in an indoor tank with a sunroof (facility A) and the other male was held in an indoor tank without a sunroof (facility B). Water temperatures in both facilities reflected seasonal changes during the study period with a minor difference in the fluctuation pattern. Testosterone levels of the male in facility A were higher from spring to summer every year and exhibited a 12-month cycle. The female showed estrus cycles in 1-month intervals from summer to winter, excluding 2 anestrus years. In contrast, the period of higher testosterone levels of the male in facility B gradually initiated earlier over the years under a constant photoperiod (11.5L:12.5D) and exhibited a 9-month cycle during the first 52 months. After changing the light conditions to a natural photoperiod, its testosterone levels were high from early spring to summer for 3 consecutive years and exhibited a 12-month cycle. Our results showed that under a constant artificial photoperiod, the male in facility B failed to recognize the seasonal changes of a natural external environment, resulting in a 9-month, free-running hormone cycle.

Multi-year patterns in testosterone, cortisol and corticosterone in baleen from adult males of three whale species

“…testosterone in males, 17β-estradiol in females; Norris and Lopez, 2011 ). In males, seasonal testosterone patterns have been well-documented in many terrestrial mammals as well as pinnipeds and even several odontocete (toothed) whales ( Wells, 1984 ; Kellar et al , 2009 ; Funasaka et al , 2011 , 2018 ; O’Brien et al , 2016 ; Richard et al , 2017 ). However, cetaceans are cryptic species that are difficult to observe via traditional techniques, and seasonal patterns in many large whales are still incompletely understood, particularly the mysticete whales.…”

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

“…The circulating levels of male and female gonadal steroid hormones provide valuable information for evaluating the reproductive activity of small captive cetaceans [ 19 ], such as common bottlenose dolphins Tursiops truncatus [ 20 , 32 , 35 , 36 , 41 ], killer whales Orcinus orca [ 30 ], white whales Delphinapterus leucas [ 31 ], Pacific white-sided dolphins Lagenorhynchus obliquidens [ 33 ], and finless porpoises Neophocaena asiaeorientalis [ 12 ]. Atkinson et al .…”