A presença de intersexo em Brycon orbignyanus (Teleostei: Bryconidae): da diferenciação sexual, fisiologia a características sexuais secundárias
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Data
2022-02-01
Autores
Quirino, Patricia Postingel
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
A piracanjuba, Brycon orbignyanus (Bryconidae), é uma espécie reofílica de grande interesse comercial na aquicultura, porém está criticamente ameaçada na natureza devido as ações antrópicas. Assim, este trabalho teve como objetivo estudar a diferenciação sexual até a maturidade reprodutiva em B. orbignyanus cultivados em sistemas de recirculação de água, a fim de promover conhecimentos para produção e conservação da espécie. Deste modo, foi realizada uma reprodução induzida através de reprodutores previamente selecionados de B. orbignyanus na Estação de Aquicultura da U.H.E. de Promissão – AES – Tietê, Promissão/SP. Com um mês de idade foram transferidos para o Laboratório de Ictiologia Neotropical (UNESP/FEIS), onde foram mantidos em condições controladas de cativeiro (27 ± 0,5 °C, pH 6,5 ± 0,6 e amônia 0,25 ±0,10 ppm.). Assim que atingiram dois meses de idade, foram realizadas coletas mensais das gônadas, fígado e sangue dos espécimes (n=15) até que atingissem um ano, seguidas por coletas posteriores com dois e três anos de idade. Aos três meses de idade, as gônadas até então indiferenciadas, dão origem a fêmeas (15.88 ± 1.31 cm comprimento total), enquanto que em machos a diferenciação ocorre apenas aos cinco meses de idade (18.01 ± 0.10 cm comprimento total). No entanto, parte das fêmeas diferenciadas sofrem um processo de inversão sexual, passando por um período de remodelamento gonadal, dando origem a espécimes intersexos (22.5 ± 1.06 cm comprimento total), pois possuem características gonadais femininas e masculinas ao mesmo tempo. Com a finalização do remodelamento gonadal, espécimes intersexo tem as características femininas nas gônadas regredidas, formando epitélio germinativo testicular e dando origem ao que foi denominado machos secundários. Ademais, a diferenciação sexual em B. orbignyanus, embora quantificada temporalmente, também é influenciada pelo crescimento dos espécimes e pela interação de fatores fisiológicos. Os níveis plasmáticos de testosterona (T) ao longo da ontogênese gonadal no primeiro ano de vida destes espécimes são maiores do que de 11-cetotestosterona (11KT), com exceção de machos com maturidade sexual atingida. Dentro dos hormônios esteroides quantificados neste trabalho, 11KT é o provavelmente o hormônio diretamente envolvido na inversão sexual ocorrida nas fêmeas. Ademais, machos primários e machos secundários desenvolvem características sexuais secundárias igualmente, sendo que machos que apresentam nadadeira anal com seis raios ou mais com espículas estão Aptos a Espermiar.
Piracanjuba, Brycon orbignyanus (Bryconidae), is a rheophilic species of great commercial interest in aquaculture, but it is critically endangered in nature due to anthropic actions. Considering this, the present work aims to study the morphophysiology of sexual differentiation until reproductive maturity in B. orbignyanus cultivated in water recirculation systems to provide knowledge for the production and conservation of this species. To do so, an induced reproduction was carried out using previously selected breeders of B. orbignyanus at the Aquaculture Station of the Hydroelectric Power Plant of Promissão – AES – Tietê, Promissão/SP. At one month of age, the fish were transferred to the Neotropical Ichthyology Laboratory (UNESP/FEIS), where they were kept in captivity under controlled conditions (27 ± 0.5 °C, pH 6.5 ± 0.6 and ammonia 0.25 ± 0.10 ppm). As soon as they reached two months of age, samples began being collected from their gonads, liver and blood (n=15), until they reached one year of age, followed by further collections at two and three years of age. At three months of age, the undifferentiated gonads give rise to females (15.88 ± 1.31 total length), whereas in males the differentiation only occurs at five months of age (18.01 ± 0.10 total length). However, part of the differentiated females undergo a process of sexual inversion, going through a period of gonadal remodeling, and then giving rise to intersex specimens (22.5 ± 1.06 total length), as they have female and male gonadal characteristics at the same time. At the end of this process, intersex specimens have the female characteristics in the regressed gonads, forming testicular germinal epithelium and giving rise to the so-called secondary males. Furthermore, the sexual differentiation in B. orbignyanus, although quantified over time, is also influenced by the growth (total length) of the specimens and by the interaction of physiological factors. Plasma testosterone (T) levels throughout gonadal ontogenesis in the first year of life of these specimens are higher than that of 11-ketotestosterone (11KT), except for males that reached sexual maturity. Among the steroid hormones quantified in this work, 11KT is probably the hormone directly involved in the sex inversion that occurred in the females. Furthermore, primary males and secondary males develop secondary sexual characteristics equally, males that present an anal fin with six rays or more with hooks are Spawning Capable.
Piracanjuba, Brycon orbignyanus (Bryconidae), is a rheophilic species of great commercial interest in aquaculture, but it is critically endangered in nature due to anthropic actions. Considering this, the present work aims to study the morphophysiology of sexual differentiation until reproductive maturity in B. orbignyanus cultivated in water recirculation systems to provide knowledge for the production and conservation of this species. To do so, an induced reproduction was carried out using previously selected breeders of B. orbignyanus at the Aquaculture Station of the Hydroelectric Power Plant of Promissão – AES – Tietê, Promissão/SP. At one month of age, the fish were transferred to the Neotropical Ichthyology Laboratory (UNESP/FEIS), where they were kept in captivity under controlled conditions (27 ± 0.5 °C, pH 6.5 ± 0.6 and ammonia 0.25 ± 0.10 ppm). As soon as they reached two months of age, samples began being collected from their gonads, liver and blood (n=15), until they reached one year of age, followed by further collections at two and three years of age. At three months of age, the undifferentiated gonads give rise to females (15.88 ± 1.31 total length), whereas in males the differentiation only occurs at five months of age (18.01 ± 0.10 total length). However, part of the differentiated females undergo a process of sexual inversion, going through a period of gonadal remodeling, and then giving rise to intersex specimens (22.5 ± 1.06 total length), as they have female and male gonadal characteristics at the same time. At the end of this process, intersex specimens have the female characteristics in the regressed gonads, forming testicular germinal epithelium and giving rise to the so-called secondary males. Furthermore, the sexual differentiation in B. orbignyanus, although quantified over time, is also influenced by the growth (total length) of the specimens and by the interaction of physiological factors. Plasma testosterone (T) levels throughout gonadal ontogenesis in the first year of life of these specimens are higher than that of 11-ketotestosterone (11KT), except for males that reached sexual maturity. Among the steroid hormones quantified in this work, 11KT is probably the hormone directly involved in the sex inversion that occurred in the females. Furthermore, primary males and secondary males develop secondary sexual characteristics equally, males that present an anal fin with six rays or more with hooks are Spawning Capable.
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Palavras-chave
Epitélio germinativo, Espículas, Epitélio germinativo, Piracanjuba, Remodelamento gonadal, Bony hooks, Germinal epithelium, Gonadal remodeling, Sex inversion,