Ultrastructure of the ovarian follicles in the placentotrophic Andean lizard of the genus Mabuya (Squamata: Scincidae)
Abstract
We studied the ultrastructural organization of the ovarian follicles in a placentotrophic Andean lizard of the genus Mabuya. The oocyte of the primary follicle is surrounded by a single layer of follicle cells. During the previtellogenic stages, these cells become stratified and differentiated in three cell types: small, intermediate, and large globoid, non pyriform cells. Fluid-filled spaces arise among follicular cells in late previtellogenic follicles and provide evidence of cell lysis. In vitellogenic follicles, the follicular cells constitute a monolayered granulosa with large lacunar spaces; the content of their cytoplasm is released to the perivitelline space where the zona pellucida is formed. The oolemma of younger oocytes presents incipient short projections; as the oocyte grows, these projections become organized in a microvillar surface. During vitellogenesis, cannaliculi develop from the base of the microvilli and internalize materials by endocytosis. In the juxtanuclear ooplasm of early previtellogenic follicles, the Balbiani's vitelline body is found as an aggregate of organelles and lipid droplets; this complex of organelles disperses in the ooplasm during oocyte growth. In late previtellogenesis, membranous org...Continue Reading
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How the ovarian follicle of Podarcis sicula recycles the DNA of its nurse, regressing follicle cells
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