Histochemical and electron microscopic observations on the sperm receptacles in the garter snake oviduct

The sperm storage receptacles in the oviduct of the garter snake, Thamnophis sirtalis , were studied using histological, histochemical, and electron microscopic techniques. The receptacles are located in the posterior infundibulum and are readily distinguished from other structures within the oviduct. The luminal epithelium consists of secretory cells and ciliated cells. The latter cell type also lines the ducts leading to the receptacles. The distribution of lipids, carbohydrates, and several enzymes (succinic dehydrogenase, acid and alkaline phosphatases, nonspecific esterase, lipase, sorbitol dehydrogenase) in the infundibulum is described. At the electron microscopic level sperm heads are seen to be closely associated with the surface of receptacle cells, often indenting the luminal plasma membrane. The possibility of a “Sertoli cell‐like” relationship is discussed. Formation of cytoplasmic vacuoles in receptacle cells is temporally associated with ovulation and may be part of a mechanism for sperm release from receptacle cells. No contractile elements were observed immediately around the receptacles. Evidence is presented which suggests that free fructose and glucose are produced by the oviduct, possibly to be utilized for sperm metabolism at the time of ovulation and sperm release.