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SEASONAL CHANGES IN THE GROSS ANATOMY AND HISTOLOGY OF THE OVIDUCT IN AN OVIPAROUS LIZARD, SCELOPORUS UNDULATUS

Abstract

The seasonal nature of reproductive activity in Eastern Fence Lizards, Sceloporus undulatus, provides an opportunity to examine environmental and hormonal influences on reproductive tract anatomy and physiology. Female fence lizards engage in oogenesis, mating, egg shelling, and egg laying in the spring and summer months, with a period of relative quiescence in the following fall and winter. The oviduct is the site of fertilization and is regionally specialized to receive ovulated eggs, store sperm, support early embryonic development, secrete eggshell proteins and minerals, and oviposit shelled eggs. Seasonal changes in oviduct morphology are evident, but there is limited detailed information about the histological changes corresponding to changes in oviduct function. While descriptive criteria for ovarian and follicular stages have been established, similar staging criteria for the seasonal recrudescence and subsequent regression of the oviduct remain poorly documented. In order to examine these changes, adult female lizards were captured across a sampling period between 2020 and 2023 from the Oconee National Forrest, GA, USA. The oviducts were dissected, weighed, and photographed using stacked imaging for examination of gross morphology. Subsequently, the right oviduct was embedded in paraffin wax, sectioned with a manual microtome, and stained with hemoxylin and eosin. The oviducts of reproductively active lizards exhibit greater epithelial cell height, increased muscularity, and larger and greater abundance of shell glands in comparison to the oviducts of nonreproductive lizards. Our results provide a detailed description of the gross and histological changes in the oviducts corresponding to the annual reproductive cycle of an oviparous lizard in central Georgia. Due to the expansive geographic range of Eastern Fence Lizards, these data will serve as a point of reference for future studies investigating the effects of geographic variation and climate change on reproductive physiology.

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