Seasonal Variation of Testicular Tissue in Northern Rough Greensnakes,Opheodrys a. aestivus,from Alabama

Abstract

Gamete production is a fundamental component of the reproductive cycle of an organism. Studies dedicated to the testicular cycle in mammals and birds vastly outnumbers those discussing the process in reptiles. To help increase the availability of such knowledge for reptiles, we histologically examined the testicular cycle of Opheodrys a. aestivus (Northern Rough Greensnake) from populations in Alabama. We measured seminiferous tubule diameter and seminiferous tubule epithelial height from 30 specimens. The individuals in our sample exhibited small seminiferous tubule diameters in spring followed by increases in summer. By October, the lumen was mostly empty of sperm because they had migrated to the vas deferens for winter storage. Seminiferous tubule epithelial height was significantly correlated with seminiferous tubule diameter. Using AIC model selection, we compared both additive and interactive models to determine if either seminiferous tubule diameter or season influenced seminiferous tubule epithelial height. We found that only seminiferous tubule diameter was a significant predictor of seminiferous tubule epithelial height. Like other temperate snakes, Northern Rough Greensnakes in Alabama have postnuptial spermatogenesis where sperm are produced in the summer following spring mating. Future studies of this species need to investigate the testicular cycle in other parts of its geographic distribution to see if this monthly pattern is consistent.