ELF, P.*; RHEN, T.; FIVIZZANI, A.; CREWS, D.; University of Minnesota, Crookston; University of North Dakota, Grand Forks; University of North Dakota, Grand Forks; University of Texas, Austin: Inter- and Intra-seasonal differences in yolk hormone levels in eggs from the leopard gecko, Eublepharis macularius.
Previous reports have documented seasonal clutch differences in yolk hormone levels, specifically estradiol in the painted turtle, Chrysemys picta, a TSD reptile, that were correlated with differences in male/female ratios of the hatchlings. The leopard gecko is another TSD reptile that lays more than one clutch of eggs per season. Since we have implicated yolk steroid hormones in the sex determination process in TSD species, we were interested in determining whether or not there were variations in hormone concentrations in extraembryonic material among clutches of eggs produced by a female leopard gecko in a single season, and also determining any differences between clutches of eggs produced by a female in different seasons. Eggs were collected upon lay, labeled for female and date and frozen until analyses. Eggs were later dissected, any embryos present were collected for staging, and extraembryonic material was collected for extraction and quantification of hormones. The extracts were column separated and androstenedione, dihydrotestosterone, estradiol and testosterone were all measured using very specific I125labeled radioimmunoassays. Results indicate that some females did have significant variation in hormone levels among different clutches within a season, but the nature of the differences appears to vary among females. There were also significant differences between hormone levels from individual females from one season and the next, but these also varied with female identity. pelf@mail.crk.umn.edu
