Accumulation of yolk in a caecilian (Gegeneophis ramaswamii) oocyte: A light and transmission electron microscopic study

Abstract

There is a paucity of information on the female reproductive biology of the caecilian amphibians when compared with the other vertebrate groups. Hence, the accumulation of nutrient reserves in the form of yolk and formation of yolk platelets were studied in Gegeneophis ramaswamii, adopting light microscopic histological and transmission electron microscopy analysis. Previtellogenic as well as vitellogenic follicles were observed in appropriate preparations. On the basis of the source and the routes of entry, we identified four types of yolk precursor materials, precursors 1 to 4. The earliest material appearing in the oocyte consists of abundant lipid vesicles during the previtellogenic phase, i.e., much before the follicular epithelium is fully established. This is a contribution from the oocyte mitochondria, which we identified as yolk precursor material 1, and it is autosynthetic. Once the follicle cell-oocyte interface is fully established, there is an accumulation of the principal component of the heterosynthetic yolk by sequestration from the blood through the intercellular spaces between follicle cells in a pinocytic process. This we identified as yolk precursor material 2. There was also an indication of a lipidic yolk material synthesis in the follicle cells sequestered from maternal blood through the follicle cells in an endocytic process in which the macrovilli of follicle cells and the microvilli of the oocyte play a role. This we identified as yolk precursor material 3. Contribution to the yolk of peptidic, glycosidic, and/or lipidic material synthesized in the vitellogenic oocyte was also indicated. This we identified as yolk precursor material 4. The sequential development of intercellular associations and indications of synthesis/sequestration of the yolk have been traced. Thus, we report the mechanistic details of synthesis/sequestration of the yolk materials in a caecilian.

Light and transmission electron microscopic structure of skin glands and dermal scales of a caecilian amphibian Gegeneophis ramaswamii, with a note on antimicrobial property of skin gland secretion

“…The animal handling techniques were as described by Beyo, Divya, Oommen, and Akbarsha (2008). Freshly dissected skin samples were F I G U R E 1 Gegeneophis ramaswamii [Color figure can be viewed at wileyonlinelibrary.com] washed thoroughly in amphibian ringer solution (6.6 g NaCl, 0.15 g KCl, 0.15 g CaCl 2 , and 0.2 g NaHCO 3 added to 1 L distilled water and then fixed in 2.5% glutaraldehyde solution.…”

An insight into the skin glands, dermal scales and secretions of the caecilian amphibian Ichthyophis beddomei

“…The animal handling techniques were adopted from Beyo et al, 2008 , Arun et al, 2018 . The dissected skin samples (n = 3) were washed in amphibian Ringer solution [6.6 g NaCl, 0.15 g KCl, 0.15 g CaCl 2 , and 0.2 g NaHCO 3 added to 1L distilled water], followed by fixation in 2.5% glutaraldehyde solution, post-fixation in 1% osmium tetroxide, and embedding in methacrylate (Sigma Chemical Co., St. Louis, MO).…”

Aspectos metabólicos e endócrinos do ciclo reprodutivo de cecílias dermatófagas Siphonops annulatus (Amphibia, Gymnophiona, Caeciliidae) mantidas em cativeiro

“…Em Xenopus laevis, durante o período vitelogênico, 80-90% do total de proteínas do oócito é derivado da captação de vitelogenina do plasma, enquanto os outros 10-20% são sintetizados pelo próprio oócito pelo processo de autossíntese (OPRESKO & WILLEY, 1987). O mesmo foi observado na cecília G. ramaswamii (BEYO et al, 2008b).…”

“…Ichthyophis tricolor e Gegeneophis ramaswamii (BEYO et al, 2007a(BEYO et al, , 2007b(BEYO et al, , 2008a(BEYO et al, , 2008b (BEYO et al, 2007a(BEYO et al, , 2007b. Deste modo, o oócito se associa às células somáticas granulosas e se torna uma estrutura funcional conhecida como folículo ovariano.…”