Oocyte structure and ultrastructure in the Mexican silverside fish Chirostoma humboldtianum (Atheriniformes: Atherinopsidae)

Abstract

the structural and ultrastructural features of gonads from endemic Mexican fish have received scarce attention. This study describes the histological and ultrastructural characteristics of the oocyte in Chirostoma humboldtianum. The ovary is asynchronic, and as such, most phases of oocyte development are found in the same ovary. The complete process of oogenesis was divided in five stages: oogonium and folliculogenesis, primary growth, cortical alveoli and lipid inclusions, vitellogenesis and maturation. The presence of big filaments, which appear at the end of primary growth, induces some common follicular adaptation. During primary growth, abundant ribosomes, rough endoplasmic reticulum, and mitochondria are grouped in the cytoplasm. At the end of this stage, the Z1 layer of the chorion is developed, while microvilli start to be evident as well. In the cortical alveoli and lipid droplets phase, intense PAS positive vesicles, some of them containing nucleoid material, are observed in the peripheral cytoplasm and the lipid droplets take a more central position. In vitellogenesis, the proteic yolk accumulates in a centripetal way while the chorion is completely formed. In maturation, the germinal vesicle migrates to the animal pole, meiosis is restored, and there is nuclear breakdown. The oocyte increases its size and holds some oil droplets and a big fluid mass of yolk. On the outside, filaments surround the oocyte completely. Rev. Biol. Trop. 56 (4): 1825-1835. Epub 2008 December 12.

Oocyte development and ovarian maturation of the black triggerfish, Melichthys niger(Actinopterygii: Balistidae) in São Pedro e São Paulo Archipelago, Brazil

“…Although this stage was considered as a phase included in the primary growth stage by McMillan (2007), in this study it was considered a separate stage due to the clear differentiation between them. The nucleoli concentration in the vicinities of the inner nucleus membrane, i.e., on its periphery, observed at this stage, has been reported for several teleosts, for species inhabiting marine environments as well as freshwater (Wallace & Selman, 1981;Tricas & Hiramoto, 1989;Ganeco et al, 2001;Abdalla & CruzLandim, 2003;Honji et al, 2006;Cárdenas et al, 2008). The cortical alveoli and vitellogenic stages were similar to those described by McMillan (2007).…”

“…Differently from observed in other cases, on this study, oocytes from cortical alveoli stage were marked also by presenting a discrete thin zona pellucida, similar to other teleosts (Mesa et al, 2007). Although this structure in other species may appear only in the late previtellogenic stage (Cárdenas et al, 2008) or only in later stages of the oocyte development (Tricas & Hiramoto, 1989;Chaves, 1992). The vitellogenic stage of black triggerfish, as in most teleosts, was marked by a significant increase in the oocyte diameters, mainly by the inclusion of lipid droplets in cell cytoplasm, a process that begins in the previous stage by the exogenous accumulation of proteins (Wallace & Selman, 1981;Abascal & Medina, 2005).…”

Estructura y la ultraestructura del ovario de Cichlasoma urophthalmus (Perciformes: Cichlidae)

“…Las células de la teca están compuestas de Tejido Conectivo y vasos sanguíneos con algunos desmosomas que interconectan las células. Trabajos previos proponen que estas células podrían producir precursores de esteroides (andrógenos) y las células granulosas podrían convertir andrógenos a 17 estradiol u otros mediadores esteroideos (Nakamura & Nagahama 1993, Nagahama 1997, Devlin & Nagahama 2002, Cárdenas et al 2008. Las células granulosas poseen organelos típicos de células secretoras de proteínas lo cual sugiere funciones adicionales en la síntesis de la cubierta y la producción de enzimas involucradas en la conversión de precursores de esteroides.…”

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“…It appears that the increase in weight and ovarian volume is related to the vitellogenic stages in the first oocyte development (Branco, Viana, Félix, Véras, & Hazin, 2013). The cortical alveoli stage was observed in the ovaries of P. stridens at the end of the previtellogenic stage; nevertheless, this structure in other species may appear only in the late previtellogenic stage (Cardenas, Chávez, González, Espinosa, & Jiménez-garcía, 2008) or only in later stages of the oocyte development (Tricas and Hiramoto, 1989). The vitellogenic stage of P. stridens, as in the majority of teleosts, was marked by a significant increase in the oocyte sizes, mainly by the inclusion of lipid droplets in cell cytoplasm, a process that begins in the previous stage (II, III and IV) by the exogenous accumulation of proteins ( Branco et al, 2013).…”