REPRODUCTIVE HORMONE PATTERNS IN MALE AND FEMALE COWNOSE RAYS (RHINOPTERA BONASUS) IN AN AQUARIUM SETTING AND CORRELATION TO ULTRASONOGRAPHIC STAGING

Abstract Reproductive management of cownose rays (Rhinoptera bonasus) under professional care plays an important role in conservation of the species, but hormone and ultrasonographic analyses of their 12-mo reproductive cycle have not been documented previously. Plasma reproductive hormone concentrations (17B-estradiol, progesterone, testosterone, and androstenedione) were measured monthly via radioimmunoassay for 1 yr in an aquarium-managed population of adult females (n = 15) and males (n = 5). Ultrasounds of the uterus were performed each month at the time of sample collection to identify gestation stage (0–5) based on a previously developed in-house staging system. Stages were correlated to hormone concentrations to track progression through pregnancy. Thirteen females were reproductively active, and each produced one pup in March–June, similar to timing for free-ranging populations. Female estradiol increased steadily throughout gestation from stages 0 to 5, while progesterone, testosterone, and andr...