STRUCTURE, FUNCTION, AND EVOLUTION OF THE OVIDUCTS OF SQUAMATE REPTILES, WITH SPECIAL REFERENCE TO VIVIPARITY AND PLACENTATION

摘要: In lizards and snakes, the oviducts function in fertilization, sperm storage, egg transport, eggshell deposition, maintenance of early embryo, expulsion or fetus. viviparous forms they also contribute to placentae responsible for gas exchange nutrient provision Dissections species 30 genera coupled with data from literature indicate that squamate vary interspecifically seven macroscopic features, including extent nature regional differentiation, vascular supply, topographic asymmetry, number oviducts, vaginal pouches, relationship cloaca. The uterus, infundibulum, vagina differ histologically their epithelia, glands, myometrial layers. Season cyclicity occurs all three oviductal regions, most prominently is under endocrinological control. Regional cytological specializations reflect diverse functions performed by oviduct. Definitive evidence albumen production resorption lacking. squamates, uterine may facilitate maternal-fetal exchange: an attenuated epithelium, reduced glands (and a shell membrane), increased vascularization. Contrary previous reports, pregnant uteri show no epithelial erosion capillary exposure. Specializations fetus include mucosal hypertrophy, enlarged glandular multicellular whose secretions are absorbed chorioallantois. Comparisons other amniotes squamates inherited oviduct as organ capabilities uptake oviposition. Other features have evolved convergently among squamates: infundibular receptacles, unilateral loss, gestation, placentation, placentotrophy. Cladistic analysis indicates associated deposition tertiary investments reptiles evolutionary convergence well secondary simplification, rather than unidirectional trend towards specialization.