Meeting Abstract
Steroid hormones play a crucial role in the initiation and maintenance of pregnancy in live-bearing vertebrates. Despite the diversity of maternal provisioning strategies, little research has investigated embryonic steroidogenesis. Pregnant Round Stingrays (Urobatis halleri) were captured from two sites in southern California and paired samples of maternal plasma and uterine fluid (histotroph) were analyzed for a suite of 11 steroid hormones using a liquid chromatography system connected with tandem mass spectrometer equipped with electrospray ionization source. More steroids were detected (at higher concentrations) in histotroph samples compared to maternal plasma. In particular, histotroph progesterone and testosterone were highest during early gestation, coinciding with the appearance of secondary sex characteristics in embryos (i.e. presence/absence of claspers). This study is one of the first to examine steroid hormones in elasmobranch histotroph, and suggests that embryonic steroidogenesis begins early in development and is likely to influence sexual differentiation.
