Female Red-sided Garter Snakes Research Articles

Effects of prostaglandin F2 alpha on sexual behavior and ovarian function in female garter snakes (Thamnophis sirtalis parietalis).

Sexual behavior, plasma steroid hormone levels, and ovarian growth of female red-sided garter snakes (Thamnophis sirtalis parietalis) treated with prostaglandin F2 alpha (PGF2 alpha; 0.5-5.0 micrograms/g BW) were observed. The largest dose of PGF2 alpha significantly inhibited receptivity (mating) within 0.5 h of treatment and resulted in a significant decrease in sexual attractively 24 h later. These changes precisely parallel those seen in females that have mated. Lower doses of PGF2 alpha significantly increased the latency of females to mate by 3-fold in both the laboratory and the field. In contrast to the inhibitory effects of PGF2 alpha on sexual behavior, females injected with PG had levels of steroid hormones (progesterone, testosterone, 17 beta-estradiol, and corticosterone) similar to those in unmated controls 24 h after treatment, while females that had mated 24 h previously had significantly elevated plasma levels of 17 beta-estradiol. There was no significant difference in the incidence of vitellogenesis 6-8 weeks later among unmated females, unmated females treated with PG, and mated females. These results suggest that complex neuroendocrine responses occur after mating. One response may involve mating-induced release of PGs and suppression of sexual behavior, while a second independent response may involve a PG-independent mechanism that influences ovarian function. These findings are interpreted within the context of the garter snake's reproductive physiology and ecology.

Ovarian development in red-sided garter snakes, Thamnophis sirtalis parietalis: Relationship to mating

Female red-sided garter snakes ( Thamnophis sirtalis parietalis) exhibit a complex array of behavioral patterns. females may mate once, more than once, or not at all in the spring of the year, and a high percentage of female may mate in late summer before returning to winter hibernacula. The role of mating in the induction of ovarian growth in this species is complicated by this pattern of spring and late summer mating. Females hibernatedin the laboratory that mate on emergence in the spring exhibit higher frequencies of ovarian recrudescence than females that do not mate when exposed to males. Yet neither male courtship nor mating in the spring is required for ovarian development. However, mated and unmated females collected in the field in the spring of the year do not differ in frequencies of ovarian recrudescence. Ovarian growth in unmated females collected in the spring parallels the incidence of mating in the previous late summer. Thus, mating may influence the initiation of ovarian growth, but the effect can occur immediately (from spring mating) or be stored over winter (from late summer mating). Large year-to-year variation in reproductive rates of female red-sided garter snakes suggests that other factors such as nutrition and stored energy reserves may modify the effects of mating on ovarian growth.

Effects of early sex steroid hormone treatment on courtship behavior and sexual attractivity in the red-sided garter snake, Thamnophis sirtalis parietalis

Previous research has shown that exogenous androgen fails to elicit courtship (chin-rubbing) behavior in adult male or female red-sided garter snakes (Thamnophis sirtalis parietalis). However, gonadectomized and intact newborn male and female red-sided garter snakes given silastic capsules containing testosterone exhibit chin-rubbing behavior; gonadectomized and untreated animals do not show this behavior. Both males and females also exhibit chin-rubbing behavior when treated with testosterone as yearlings. Hibernation stimulates chin-rubbing behavior only in males that have received androgen treatment as a neonate or as a yearling. Previous research has also shown that adult females, but not adult males, are courted if given estrogen treatment. Both newborn males and females will elicit chin-rubbing behavior from adult males if given estrogen treatment, indicating production and release of an attractiveness pheromone characteristic of adult females. Male red-sided garter snake breed for the first time on emergence from their second hibernation, whereas females probably do not breed until their third year of life. These data suggest that in the red-sided garter snake, a species that exhibits a dissociated reproductive tactic, sex steroid hormones act to organize central nervous system mechanisms subserving courtship behavior such that temperature, and not hormonal, fluctuations activate sexual behavior in the adult organism.

Mating in the red-sided garter snake, Thamnophis sirtalis parietalis: differential effects on male and female sexual behavior

Female red-sided garter snakes, Thamnophis sirtalis parietalis, become unattractive to most males after mating in the field and in the laboratory. Male red-sided garter snakes vary in their latencies to court attractive females following copulation, with courtship resuming in minutes to hours. Unsuccessful males in mating balls disperse from mating pairs, but are not residually inhibited from courting attractive females. These patterns of behavior indicate that males have evolved mechanisms to maximize opportunities for copulation with several females, while females mate only once per season.

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.