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Knowledge concerning the dynamics of reproductive events for tropical reptiles is limited. Therefore, little is known about the reproductive physiology of the ball python, Python regius, and the Brazilian rainbow boa, Epicrates cenchria cenchria. Descending from a common ancestor yet evolving under different environmental constraints resulted in two different reproductive modes, oviparity and viviparity, respectively.
The objective of this project was to describe aspects of the reproductive physiology of these two species. In reptiles, as in other all non-mammalian vertebrates, the vitellogenic process defines the ovarian cycle. Ultrasound image analysis of the oocytes allowed the determination of changes in oocyte size and composition during vitellogenesis, providing, for the first time, details of the complexity of the vitellogenic process. Because hormones drive physiological, morphological and behavioral systems, plasma concentrations of estradiol and progesterone were determined and compared across the reproductive cycle. Then, oocyte dynamics within the reproductive tract were correlated with the pattern of reproductive hormones.
The reproductive season for captive male Brazilian rainbow boas and ball pythons was based on seasonality of circulating testosterone semen collections of viable sperm and observations of courtship and mating. The pattern of reproduction for each species was thus elucidated.
The ability to determine the timing of ovarian and testicular events provided insight into the reproductive dynamics for each species. Details included defining seasonality, oocyte development and compositional changes over the reproductive season, determining the approximate time of fertilization, and monitoring development of eggs in the ball python (oviparous) and of embryos in the Brazilian rainbow boa (viviparous). Physiological, morphological and behavioral data for these species provided details of the reproductive cycle necessary for future assisted reproductive techniques and captive management programs.