Blackburn D G
Department of Biology, Trinity College, Hartford, Connecticut 06106, USA.
J Exp Zool. 1998;282(4-5):560-617.
In lizards and snakes, the oviducts function in fertilization, sperm storage, egg transport, eggshell deposition, maintenance of the early embryo, and expulsion of the egg or fetus. In viviparous forms they also contribute to placentae responsible for gas exchange and nutrient provision to the fetus. Dissections of species of 30 genera coupled with data from the literature indicate that squamate oviducts vary interspecifically in seven macroscopic features, including the extent and nature of regional differentiation, vascular supply, topographic asymmetry, number of oviducts, vaginal pouches, and relationship to the cloaca. The uterus, infundibulum, and vagina differ histologically in their epithelia, glands, and myometrial layers. Season cyclicity occurs in all three oviductal regions, most prominently in the uterus, and is under endocrinological control. Regional and cytological specializations reflect the diverse functions performed by the oviduct. Definitive evidence for oviductal albumen production and egg resorption is lacking. In viviparous squamates, three uterine specializations may facilitate maternal-fetal gas exchange: an attenuated epithelium, reduced uterine glands (and a reduced shell membrane), and increased vascularization. Contrary to previous reports, pregnant uteri show no epithelial erosion or capillary exposure. Specializations for nutrient provision to the fetus include mucosal hypertrophy, enlarged glandular epithelia, and multicellular glands whose secretions are absorbed by the chorioallantois. Comparisons with other amniotes indicate that squamates inherited the oviduct as an organ with capabilities for egg uptake and transport, fertilization, eggshell deposition, and oviposition. Other features have evolved convergently among squamates: infundibular sperm receptacles, unilateral oviduct loss, uterine gestation, placentation, and specializations for placentotrophy. Cladistic analysis indicates that oviductal features associated with deposition of tertiary egg investments in reptiles reflect evolutionary convergence as well as secondary simplification, rather than a unidirectional trend towards increased specialization.
在蜥蜴和蛇类中，输卵管具有受精、精子储存、卵子运输、蛋壳形成、早期胚胎维持以及卵子或胎儿排出等功能。在胎生种类中，输卵管还参与形成负责气体交换和为胎儿提供营养的胎盘。对30个属的物种进行解剖，并结合文献数据表明，有鳞目动物的输卵管在七个宏观特征上存在种间差异，包括区域分化的程度和性质、血管供应、地形不对称、输卵管数量、阴道囊以及与泄殖腔的关系。子宫、漏斗部和阴道在组织学上，其上皮、腺体和肌层存在差异。所有三个输卵管区域都有季节性周期变化，在子宫中最为明显，且受内分泌控制。区域和细胞学特化反映了输卵管执行的多种功能。目前缺乏输卵管产生蛋白和卵子吸收的确切证据。在胎生有鳞目动物中，子宫的三种特化可能有助于母胎气体交换：上皮变薄、子宫腺体减少（以及壳膜减少）和血管化增加。与之前的报道相反，怀孕的子宫没有上皮侵蚀或毛细血管暴露。为胎儿提供营养的特化包括黏膜肥大、腺上皮增大以及其分泌物被绒毛膜尿囊吸收的多细胞腺体。与其他羊膜动物的比较表明，有鳞目动物继承了输卵管这一具有卵子摄取和运输、受精、蛋壳形成及产卵能力的器官。其他特征在有鳞目动物中是趋同进化的：漏斗部精子储存器、单侧输卵管缺失、子宫妊娠、胎盘形成以及胎盘营养特化。分支系统分析表明，与爬行动物三级卵投资沉积相关的输卵管特征反映了进化趋同以及次生简化，而非朝着增加特化的单向趋势。
