OVARIAN FOLLICULOGENESIS IN THE OVIPAROUS MEXICAN LIZARD CTENOSAURA-PECTINATA

The ovarian follicles of Ctenosaura pectinata exhibit a clear seasonal cycle in morphology. Early in development, each oocyte is surrounded by a granulosa composed of a single layer of cuboidal or squamous cell s and thin thecal layers. As folliculogenesis progresses, the granulos a becomes multilayered and composed of three distinct cell types. Afte r vitellogenesis begins and active sequestration of yolk into the oopl asm is initiated, the granulosa is reduced to a single cell type. We o bserved a striking change in the appearance of the ooplasm during foll iculogenesis. Early ovarian development is characterized by an ooplasm with homogeneously distributed fine fibrils, but as development progr esses, the ooplasm contains dense clumps of fibers aggregated into dis tinctive bundles. The ooplasm displays further complexity in morpholog y as previtellogenic growth continues and as different regions exhibit various combinations of fibers and vacuoles. Yolk platelet formation is complex, with distinctive stages generating platelets with varying morphologies. (C) 1996 Wiley-Liss, Inc.