Histological and morphological analyses of the sperm storage regions in Crotalus durissus terrificus

The reproductive cycle of Crotalus durissus terrificus is markedly seasonal and synchronous between individuals. The start of vitellogenesis occurs in the end of the summer and coincides with copulation. However, due to the copulation being dissociated from ovulation the sperm storage is obligatory. In viperids, sperm storage in the female reproductive tract occurs in two regions: the posterior infundibulum with sperm storage glands and the non-glandular uterus where sperm is stored in crypts by means of a phenomenon called uterine muscular twisting (UMT). The survival of sperm in the reproductive tract is still unknown. Therefore, we presents data on both sperm storage sites (posterior infundibulum and non-glandular uterus) in the C. d. terrificus, aiming to address the role of UMT in Crotalinae reproduction considering female reproductive stages, morphology and histochemistry of sperm receptacles. Storage sperm was observed in the non-glandular uterus and although the posterior infundibulum had storage receptacles, sperm were not observed in the region. Both sperm storage sites possess granules testing positive for acidic and neutral mucopolysaccharides, in both reproductive and non-reproductive females, guaranteeing conditions for sperm storage. However, the epithelium of the non-glandular uterus was more secretory for carboxylated glycosaminoglycans in vitellogenic females. Histochemical analysis revealed the possible storage capacity of sperm in the non-glandular uterus. In addition, the UMT was observed in all the females with storage sperm, assures the maintenance of sperm in the non-glandular uterus until ovulation.