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.     

Effects of group stability, male-male aggression, and male courtship behaviour on environmentally-induced ovarian recrudescence in the lizard Anolis carolinensis

Reproductively inactive, winter dormant female Anolis carolinensis were exposed to a stimulatory environmental regime while in socially stable or unstable male-female groups. In a second experiment, winter dormant females were exposed to varying amounts of male courtship and male-male aggression. Results indicate that (1) the presence of a stable dominance hierarchy among group males is necessary for male facilitation of environmentally-induced ovarian recrudescence (OR) (an unstable dominance hierarchy inhibits OR), (2) the behaviour patterns responsible for the facilitation and inhibition of environmentally-induced OR are courtship and male-male aggression, respectively, and (3) ovarian development is graded in accordance to the amount of male courtship to which the female is exposed. It is proposed that male courtship insures normal gonadotropin (GT) secretion while the absence of male courtship results in subnormal GT secretion and the presence of male-male aggression suppresses environmentally-induced GT secretions. The functional significance of the inhibition of environmentally-induced OR by male-male aggression and its possible relation to differential vernal emergence in temperate-zone reptiles is discussed.     

Mating-induced termination of behavioral estrus in the female lizard, Anolis carolinensis

Mating terminates behavioral estrus in the female lizard, Anolis carolinensis. Postcopulatory sexual inhibition was not observed in females receiving estradiol benzoate (EB) in 10-mm Silastic implants (0.025-in. i.d. × 0.047-in. o.d.). To determine the role of the ovaries in mating-induced inhibition, intact and ovariectomized females received either a 6-mm EB implant or a 0.8-μg EB injection. Ovariectomized females remained sexually receptive after copulation while intact females were no longer receptive. Progesterone was implicated in the regulation of postcopulatory sexual receptivity. Several models are proposed to explain these results, and the adaptive significance of coition-induced sexual inhibition is discussed.     

The effects of sex steroid treatments on sexual differentiation in a unisexual lizard, Cnemidophorus uniparens (Teiidae)

Cnemidophorus uniparens is a parthenogenetic unisexual species of lizard in which each individual develops as a female, making it a unique animal model for the study of sexual differentiation. In one study, administration of exogenous testosterone before and/or after hatching influenced the development of the gonads, the accessory reproductive ducts, the renal sex segment of the mesonephric kidney, and the femoral glands, a secondary sex character. Testosterone treatment also affected the cross-sectional area of the gonad and the proportions of cortical and medullary tissues present in the developing gonad. The oviducts and femoral glands of testosterone-treated individuals were hypertrophied; the collecting tubules of the kidney of these animals contained granules, an androgen-dependent, sexually dimorphic character in squamate reptiles. In another study, testosterone, dihydrotestosterone, or estradiol were administered to C. uniparens embryos. No treatment effects on gonadal development were detected on the day of hatching. However, estradiol, but not testosterone and dihydrotestosterone, stimulated development of the oviducts. Taken together these studies suggest that androgen aromatization may play a role in sexual differentiation in lizards.     

The role of the anterior hypothalamus-preoptic area in the regulation of male reproductive behavior in the lizard, Anolis carolinensis: lesion studies.

Bilateral radiofrequency lesions of the anterior hypothalamic-preoptic area (AH-POA) abolish male Courtship and Agonistic behaviors in both intact and castrated/androgen-treated Anolis carolinensis. Control lesions caudal and dorsal to the AH-POA have no effect on these behaviors. Lesions rostral to the AH-POA also cause a significant decline in the behavior of intact animals. Histological examination of testes showed that lesions including and rostral to the AH-POA cause testicular collapse and regression to initial stages of spermatogenesis, indicating interruption of gonadotropin secretion. Castration and subcutaneous implantation of androgen restores Courtship and Agonistic behaviors in Rostral and Caudal Control groups to prelesion levels, while AH-POA lesioned animals remain at their low behavioral levels. Neither AH-POA or control lesions cause significant changes in animals' body weight.     

Cloning and expression of <Emphasis Type="Italic">R-Spondin1</Emphasis>in different vertebrates suggests a conserved role in ovarian development

Background  

R-Spondin1 (Rspo1) is a novel regulator of the Wnt/β-catenin signalling pathway. Loss-of-function mutations in human RSPO1 cause testicular differentiation in 46, XX females, pointing to a role in ovarian development. Here we report the cloning and comparative expression analysis of R-SPONDIN1 orthologues in the mouse, chicken and red-eared slider turtle, three species with different sex-determining mechanisms. Evidence is presented that this gene is an ancient component of the vertebrate ovary-determining pathway.