Sperm storage in males of the Neotropical rattlesnake Crotalus durissus (Squamata: Viperidae): Structure and seasonal variation of the distal ductus deferens

In species with asynchronous reproductive cycles, where gamete production is not aligned with the mating season, either males or females must store sperm. This reproductive tactic is an obligatory feature of male rattlesnakes’ reproductive cycle due to asynchrony between spermatogenesis and mating. Given that the ductus deferens is the primary site of sperm storage in male snakes, we aimed to investigate the morphological and histochemical changes in the distal ductus deferens of C. durissus throughout its reproductive cycle. In this species, spermatogenesis begins in spring and peaks in summer, while testes regress during autumn and winter. The distal ductus deferens of 28 mature male specimens was evaluated using histomorphometric and histochemical methods. Spermatozoa were consistently observed within the lumen of the ductus deferens in almost all specimens. The principal cells of the distal region of ductus deferens reacted positively for Periodic Acid-Schiff and Bromophenol Blue. Secretions were observed in the apical region of the principal cells' cytoplasm and along the epithelium edge, which may be related to gamete maintenance. Increased secretory activity of the principal cells was observed during periods of testicular activity. A reduction in the lumen of ductus deferens occurs during testicular regression, indicating possible fluid resorption by epithelial cells. Fluid resorption might be one of the mechanisms to ensure stored sperm viability, as it provides an increase in the glycoprotein’s concentration.