The Atlantic stingray, Dasyatis sabina, has a well-defined annual reproductive cycle in Florida. We collected adult specimens over 12 months and evaluated reproductive parameters and serum levels of five steroid hormones, 17beta-estradiol (E2), progesterone (P4), testosterone (T), dihydrotestosterone (DHT), and corticosterone (CS). Female E2 peaked twice, once in mid-March to early April in association with ovulation and again in mid-June to mid-July in association with the enlargement of a second group of ovarian follicles. Female P4 peaked in early March and early April, coincident with the peak in E2. Female DHT was variable but exhibited a pattern not clearly associated with known events in the reproductive cycle. Female T and CS levels did not vary significantly through time. In males, T, DHT, and CS increased progressively through winter and spring, peaking in March when females were ovulating and when copulation probably took place. DHT concentrations were usually at least twice T levels. These three hormones peaked long after the November/December peak in gonadosomatic index. E2 was measurable in males and was highest during the period of testicular development. Male P4 varied in a pattern not clearly associated with known reproductive events.
Copyright 1997 Academic Press.