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Fig. 2. Oogenesis of Flectonotus pygmaeus and Gastrotheca riobambae. Images in (A–E) are light micrographs. Images in (F–G) are transmission electron micrographs. (A–D) Oocytes of Flectonotus pygmaeus. Diagrams on the left summarize the process of F. pygmaeus oogenesis. Nuclei are depicted in blue. (A) Section through two early oocytes with nuclei of uniform size. (B) Section through two oocytes larger than in (A). Peripheral nuclei are large in comparison with centrally located nuclei. (C) Section through a vitellogenic oocyte with three nuclei. (D) Section through a vitellogenic oocyte with the final nucleus located near the oocyte cortex. The numerous nucleoli are clustered in a karyosphere around the condensed chromosomes. Final oocyte size is 3 mm. (E–G) Oocytes of Gastrotheca riobambae at metamorphosis. (E) Section through the ovary. Cysts of oogonia surround a centrally located oocyte. The oocyte contains a single nucleus (F) Section through an ovarian cyst. Each oogonium has a single nucleus with expanded chromosomes. Oogonia were connected with cytoplasmic bridges (not shown). The total number of oogonia in the ovarian cysts of G. riobambae is unknown. (G) A previtellogenic oocyte. The Balbiani body, or mitochondrial cloud, is asymmetrically located in the cytoplasm. Chromosomes are visible in the nucleus. The white area around nuclei in (C, D) is a processing artifact. The section in (A) comes from the same oocytes shown in del Pino (1989). Images in (C, F) are reproduced from Schmid et al. (2012). Bb: Balbiani body, f: follicle envelope, Fp, Flectonotus pygmaeus; Gr, Gastrotheca riobambae; n: nucleus, nu: nucleolus. Scale bars: 20 μm (A); 100 μm (B); 200 μm (C); 40 μm (E). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.) Image published in: Del Pino EM (2018) Copyright © 2018. Image reproduced with permission of the Publisher, Elsevier B. V. Larger Image Printer Friendly View |