Cinética do desenvolvimento oocitário e caracterização ovariana da piracanjuba, Brycon orbignyanus (Bryconidae) mantidas em sistema de recirculação nos três primeiros anos de vida
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Data
2022-06-27
Autores
Olivio, Maiara Luzia Grigoli
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Universidade Estadual Paulista (Unesp)
Resumo
Os peixes neotropicais migradores, quando mantidos em cativeiros nas pisciculturas, apresentam alterações no desenvolvimento ovariano no decorrer do processo da gametogênese, impedindo a maturação final dos oócitos. Assim, se faz necessário o entendimento das distintas particularidades das células germinativas da espécie para que não aconteça a supressão da reprodução. Deste modo, o objetivo deste estudo foi analisar o desenvolvimento de oócitos primários em estágio de diplóteno da piracanjuba, Brycon orbignyanus mantidas em sistema de recirculação até o terceiro ano de vida, em relação às mudanças no tecido ovariano, quando associados às fases reprodutivas e valores do índice gonadossomático (IGS) e hepatossomático (IHS). Para tal, foram utilizadas dezoito fêmeas de B. orbignyanus com idades de quatro meses, um ano, dois anos (n = 5 por idade) e três anos (n = 3), mantidas em sistema controlado de recirculação. Os ovários e fígados foram removidos para cálculos dos índices somáticos e os ovários processados para microscopia de luz. Para a análise morfométrica e quantitativa dos oócitos foram definidos três estágios celulares presentes nas (n = 18) fêmeas, denominados por: diplóteno precoce pelo grau da basofilia nuclear, diplóteno intermediário pelo início da basofilia citoplasmática e, o perinucleolar com os nucléolos rentes ao córtex nuclear. As fêmeas de B. orbignyanus permanecem imaturas até os dois anos, apresentando no epitélio germinativo apenas oócitos pré-vitelogênicos e aos três anos de idade inicia o desenvolvimento ovariano inicial, com a presença de oócitos em vitelogênese inicial, além dos pré-vitelogênicos. Os diplótenos precoces e intermediários não diferiram significativamente quando comparados às médias do diâmetro (μm) celular e nuclear entre os espécimes, entretanto, o mesmo não ocorreu com os perinucleolares, apresentando diferenças significativas (p <0,05) entre todas as idades. Estatisticamente ocorre a maior presença dos diplótenos precoces e intermediários nas fêmeas com quatro meses e um ano de idade. Já os perinucleolares, apresentam maior número aos dois e três anos. Houve o aumento nos valores de IGS, com maior pico nas fêmeas com três anos, porém, o maior pico de IHS ocorreu nas fêmeas com quatro meses, cujo, estes fatores não são correlacionados. Conclui-se que em B. orbignyanus com diferentes idades, os diplótenos precoces e intermediários apresentam os mesmos padrões morfométricos. Por outro lado, os perinucleolares aumentam de tamanho juntamente com o desenvolvimento ovariano, conforme o avanço da idade. O aumento no volume celular coincide com o aumento do IGS, mas quando associados às fases do ciclo reprodutivo, as fêmeas de quatro meses a dois anos encontram-se imaturas e somente aos três anos alcançam à fase adulta. Este estudo forneceu informações que contribuirão no entendimento da cinética do desenvolvimento do oócito de crescimento primário em estágio de diplóteno em relação as alterações no ovário de B. orbignyanus, que serviram de base em conjunto com os dados de IGS e IHS como parâmetros indicativos da fase reprodutiva que a espécie se encontra em sistema de cultivo ao longo do tempo.
Neotropical migratory fish, when kept in captivity in fish farms, present alterations in the ovarian development during the gametogenesis process, preventing the final maturation of oocytes. Thus, it is necessary to understand the different characteristics of the germ cells of the species so that reproduction is not suppressed. Thus, the objective of this study was to analyze the development of primary oocytes at the diplotene stage of piracanjuba, Brycon orbignyanus kept in a recirculation system until the third year of life, in relation to changes in the ovarian tissue, when associated with reproductive stages and values of the gonadosomatic index (GSI) and hepatosomatic index (HSI). For this purpose, eighteen females of B. orbignyanus with ages of four months, one year, two years (n = 5 per age) and three years (n = 3) were used, kept in a controlled recirculation system. The ovaries and livers were removed for somatic index calculations and the ovaries processed for light microscopy. For the morphometric and quantitative analysis of the oocytes, three cellular stages were defined in the (n = 18) females, designated as: early diplotene by the degree of nuclear basophilia, intermediate diplotene by the onset of cytoplasmic basophilia, and perinucleolar with nucleoli flush with the nuclear cortex. The females of B. orbignyanus remain immature until two years of age, presenting in the germinative epithelium only pre-vitellogenic oocytes and at three years of age the initial ovarian development begins, with the presence of oocytes in initial vitellogenesis, besides the pre-vitellogenic ones. Early and intermediate diplotene did not differ significantly when comparing the mean cell and nuclear diameters (μm) between specimens, however, the same did not occur with the perinucleolar ones, showing significant differences (p <0.05) between all ages. Statistically, there was a greater presence of early and intermediate diplotene in females four months and one year old. The perinucleolar ones, on the other hand, present a higher number at two and three years of age. There was an increase in GSI values, with a higher peak in females at three years of age; however, the highest HSI peak occurred in females at four months of age, and these factors are not correlated. It is concluded that in B. orbignyanus at different ages, early and intermediate diplotene show the same morphometric patterns. On the other hand, perinucleolar increase in size along with ovarian development as age advances. The increase in cell volume coincides with the increase in GSI, but when associated with the phases of the reproductive cycle, females from four months to two years are immature and only at three years reach adulthood. This study provided information that will contribute to the understanding of the kinetics of primary growth oocyte development at the diplotene stage in relation to changes in the ovary of B. orbignyanus, which served as a basis in conjunction with the GSI and HSI data as parameters indicative of the reproductive phase that the species is in the culture system over time.
Neotropical migratory fish, when kept in captivity in fish farms, present alterations in the ovarian development during the gametogenesis process, preventing the final maturation of oocytes. Thus, it is necessary to understand the different characteristics of the germ cells of the species so that reproduction is not suppressed. Thus, the objective of this study was to analyze the development of primary oocytes at the diplotene stage of piracanjuba, Brycon orbignyanus kept in a recirculation system until the third year of life, in relation to changes in the ovarian tissue, when associated with reproductive stages and values of the gonadosomatic index (GSI) and hepatosomatic index (HSI). For this purpose, eighteen females of B. orbignyanus with ages of four months, one year, two years (n = 5 per age) and three years (n = 3) were used, kept in a controlled recirculation system. The ovaries and livers were removed for somatic index calculations and the ovaries processed for light microscopy. For the morphometric and quantitative analysis of the oocytes, three cellular stages were defined in the (n = 18) females, designated as: early diplotene by the degree of nuclear basophilia, intermediate diplotene by the onset of cytoplasmic basophilia, and perinucleolar with nucleoli flush with the nuclear cortex. The females of B. orbignyanus remain immature until two years of age, presenting in the germinative epithelium only pre-vitellogenic oocytes and at three years of age the initial ovarian development begins, with the presence of oocytes in initial vitellogenesis, besides the pre-vitellogenic ones. Early and intermediate diplotene did not differ significantly when comparing the mean cell and nuclear diameters (μm) between specimens, however, the same did not occur with the perinucleolar ones, showing significant differences (p <0.05) between all ages. Statistically, there was a greater presence of early and intermediate diplotene in females four months and one year old. The perinucleolar ones, on the other hand, present a higher number at two and three years of age. There was an increase in GSI values, with a higher peak in females at three years of age; however, the highest HSI peak occurred in females at four months of age, and these factors are not correlated. It is concluded that in B. orbignyanus at different ages, early and intermediate diplotene show the same morphometric patterns. On the other hand, perinucleolar increase in size along with ovarian development as age advances. The increase in cell volume coincides with the increase in GSI, but when associated with the phases of the reproductive cycle, females from four months to two years are immature and only at three years reach adulthood. This study provided information that will contribute to the understanding of the kinetics of primary growth oocyte development at the diplotene stage in relation to changes in the ovary of B. orbignyanus, which served as a basis in conjunction with the GSI and HSI data as parameters indicative of the reproductive phase that the species is in the culture system over time.
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Palavras-chave
Diâmetro celular, Fases reprodutivas, Idade, Oócitos primários, Peixes neotropicais, Sistema de recirculação, Cell diameter, Reproductive phases, Age, Primary oocytes, Neotropical fishes, Recirculation system