Pituitary Activity and Reproductive Cycle of Male Cnemidophorus sexlineatus in West Tennessee

The pituitary gland and right testis, ductus epididymidis, ductus deferens, and renal sexual segment were examined histologically in Cnemidophorus sexlineatus (six-lined racerunner) collected at monthly intervals during most spring and summer months from 1978-82 in southwest Memphis, Shelby County, Tennessee. Circulating testosterone levels were measured by radioimmunoassay in specimens collected in 1982. Adult male racerunners emerged from hibernation in April and were most active in spring-early summer. Testes, associated ducts, and renal sexual segment tubules were hypertrophied during spermatogenesis in spring-early summer and involuted during sexual quiescence in late summer. Circulating testosterone levels were highest in late spring. Mating occurred from May through August. Racerunners resumed hibernation in September. Diameters of circumtesticular Leydig cell nuclei varied seasonally, but those of interstitial Leydig cell nuclei did not. Testicular recrudescence began in late summer-fall and spermiogenesis was under way in April. Differences in size, morphology, staining properties, distribution, and seasonal cycles confirmed the presence of two types of acidophils and three types of basophils in the pars distalis. Greatest activity in acidophils and basophils, indicated by cell and/or nuclear size, occurred in spring.