Relationship between Sexual Maturity and Serum and Testis Testosterone Concentrations in Short-finned Pilot Whales Globicephala macrorhynchus

Abstract

Testes and blood samples were collected from males of the southern form short-finned pilot whale Globicephala macrorhynchus, caught by a small-type coastal whaling and the drive fishery off the Pacific coast of Japan in order to examine relationships of serum and testis concentrations of testosterone with testis weight, diameter of seminiferous tubules and density of reproductive cells. Serum and testis concentrations of testosterone ranged from 0.27 to 22.0ng/ml and from 14.4 to 287.1ng/g, respectively. Testis testosterone levels were more than 5 to 180 times higher than serum levels. Before the attainment of sexual maturity, both serum and testis testosterone levels were significantly correlated with testis weight and diameter of seminiferous tubules, but no significant relationship was shown after sexual maturity. There was no correlation between serum and testis concentrations of testosterone and density of reproductive cells in mature individuals.