Sperm transport and storage and its relation to the annual sexual cycle of the female red-sided garter snake, Thamnophis sirtalis parietalis.

Female red-sided garter snakes (Thamnophis sirtalis parietalis) store sperm from both late-summer and spring matings. Before winter dormancy, sperm are stored in specialized furrows in the vaginal portion of the oviduct, 3-6 cm anterior to the vent. After 6 weeks in dormancy, the epithelial cells lining this vaginal region hypertrophy and stain strongly with periodic acid-Schiff (PAS). This PAS+ epithelial border sloughs and associates with sperm. These aggregations of PAS+ material, which will be referred to as carrier matrices, move anteriorly through the oviduct. After 20 weeks in dormancy, most sperm are found in specialized infundibular storage regions. Spring mating induces a rapid degeneration of winter-stored sperm. Stored sperm are evacuated from infundibular storage receptacles within 6 hours after mating. Yet sperm from the spring mating are not evident in the oviduct until 24 hours after mating. Carrier matrices begin to form at this time. At 48 hours after mating, sperm, often associated with carrier matrices, appear in the infundibulum. At 40 days after mating, most sperm have moved into infundibular storage receptacles. Evidence suggests that carrier matrices not only facilitate the transport of sperm anteriorly from vaginal to infundibular regions, but also function as nutritional stores.