WYNEKEN, J.*; VAUGHAN, J.; BLAIR, K.; EPPERLY, S; Florida Atlantic University; Florida Atlantic University; Florida Atlantic University; National Marine Fisheries Service- Miami Laboratory: Natural sex ratios and posthatchling gonadal development in posthatchling loggerhead sea turtles (Caretta caretta)

Loggerhead sea turtles have environmentally determined sex. Because of their wide nesting distribution along the eastern seaboard of the United States (approximately 41�N – 24�N latitude), sex ratios can vary from rookery to rookery and across the nesting and hatching season. The loggerhead sea turtles have a subpopulation structure; we examined turtles from the two largest subpopulations (North and South). Accurate measures of sex ratios by subpopulation are important to conservation and species recovery efforts. We adapted traditional laparoscopic procedures for use in sexing very small sea turtles (~120g). Sex ratios from 10 rookeries were empirically determined using laparoscopic examination of gonad and duct morphology and verified using gonadal biopsy of a subset of the turtles. Sex ratios were significantly different from 1:1 and from theoretical predictions. Through factor analyses of morphological characters and biopsy results, we found high correlations between sex and gonadal duct size, as well as gonadal duct structure. Hence, we were able to assign sex based on gross internal morphology with high levels of confidence. We also noted seasonal shifts in gonadal maturation, but not body growth in these turtles. During the winter months, gonadal vascularity declined; the gonads became thin and white and ceased to grow while other somatic growth continued. Histologically, differentiation of the follicles and of the seminiferous tubules was retarded. Gonadal growth and differentiation resumed in the early spring.