História natural de Macrobrachium amazonicum (Heller, 1862) (Decapoda: Palaemonidae) e sua importância em reservatórios neotropicais do sudeste brasileiro
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Data
2017-09-04
Autores
Paschoal, Lucas Rezende Penido [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
O camarão amazônico Macrobrachium amazonicum apresenta populações com grande plasticidade fenotípica e alta variabilidade morfológica e reprodutiva. Três fenótipos são registrados para a espécie, por meio da avaliação de sua história de vida, características morfológicas e reprodutivas, sendo eles: (a) animais anfídromos de grande porte, e (b) hololimnéticos de grande e (c) pequeno porte. Tais características permitem que estes animais ocupem diversos ambientes aquáticos no Brasil. Nos últimos anos, registros de M. amazonicum em ambientes dulciaquícolas interiores em diversas regiões brasileiras aumentaram significativamente, principalmente em reservatórios da Bacia do Paraná. Porém, são escassas as informações sobre aspectos bioecológicos e reprodutivos em tais ambientes, assim como faltam estudos abordando a morfo-histologia dos sistemas reprodutores da espécie. Além disso, a plasticidade fenotípica de populações de M. amazonicum ainda não é totalmente compreendida. Na presente tese, os padrões anátomo-histológico dos sistemas reprodutores foram analisados nos três fenótipos da espécie, além biologia e a ecologia das populações com diferentes fenótipos provenientes de reservatórios do sudeste brasileiro. Adicionalmente, descreve-se o primeiro registro da intersexualidade e de infecção por microsporídeos em M. amazonicum. Independentemente da história de vida e estratégia sexual adotada, todas as populações de camarão amazônico analisadas apresentam padrões anatômicos, histológicos, histoquímicos e ultraestruturais similares para seus sistemas reprodutores. No entanto, fêmeas e machos das populações de pequeno porte tendem a investir mais energia em quesitos reprodutivos, quando comparados a animais de grande porte anfídromos e hololimnéticos. Fêmeas de pequeno porte deslocam mais energia para formação de ovócitos/ovos maiores e para a produção de reservas lipídicas para larvas, enquanto que machos desse fenótipo investem energia na produção e concentração espermática em detrimento da aquisição de armas sexuais. A intersexualidade na espécie é um fenômeno raro (0,06%), associado à disfunção hormonal e/ou mutação genética. Em reservatórios neotropicais as populações hololimnéticas de M. amazonicum apresentam dois fenótipos, definidos pela aquisição de armas sexuais: (a) animais de grande e (b) pequeno porte. Pode-se constatar que a espécie é resiliente e que suas populações não apresentam grandes diferenças em sua estrutura, durante eventos de estresse hídrico. Além disso, os aspectos reprodutivos de M. amazonicum (fecundidade, taxas de aborto e frequência de fêmeas ovígeras) não são significativamente alterados pelas flutuações dos níveis de água e da pluviosidade promovidas pelo fenômeno climático “El niño”. Em algumas populações da espécie, microsporídios do gênero Inodosporus, se desenvolvem dentro das fibras musculares e promovem a “doença do camarão colorido” modificando a natação e o mecanismo de escape dos animais infectados, tornando os camarões mais susceptíveis à predação. A avaliação dos aspectos histomorfológicos e populacionais analisados nos diferentes fenótipos permitiram a compreensão e comparação de processos bioecológicos e reprodutivos para a espécie. Além disso, as lacunas envolvendo a plasticidade fenotípica de populações de M. amazonicum foram preenchidas com o presente estudo.
The Amazon river shrimp Macrobrachium amazonicum exhibits populations with great phenotypic plasticity and high morphological and reproductive variability. Three phenotypes are recorded for the species, through the evaluation of their life history, morphological and reproductive characteristics, being: (a) large amphidromous, and (b) large and (c) small hololimnetic animals. These characteristics allow these animals to occupy diverse aquatic environments in Brazil. In recent years, M. amazonicum records have increased significantly in continental freshwater environments in Brazil, mainly in reservoirs inserted at the Paraná Basin. However, information on bioecological and reproductive aspects in such environments is scarce. Also, there were no studies evaluating the histomorphology of the reproductive systems in Amazon shrimp. In addition, the phenotypic plasticity of populations of M. amazonicum is not yet fully understood. In the present thesis the histoanatomic patterns of the reproductive systems were analyzed in three phenotypes of the species. As well, the biology and ecology of populations with different phenotypes were investigated in reservoirs of the southeastern Brazil. In addition, the first record of intersexuality and microsporidiosis in the species are presented here. Regardless of the life history and sexual strategy adopted, all populations of M. amazonicum analyzed present similar anatomical, histological, histochemical and ultrastructural patterns in their reproductive systems. However, females and males of the small populations tend to invest more energy in reproductive aspects when compared to large amphidromous and hololimnetic animals. Small females displace more energy to produce larger oocytes/eggs and lipid reserves for larvae, while males of this phenotype invest energy in sperm production and concentration in the detriment of the acquisition of sexual weapons. Intersexuality in the species is a rare phenomenon (0.06%) associated with hormonal disruption and/or genetic mutation. In neotropical reservoirs the hololimnetic populations of M. amazonicum presents two phenotypes, defined by the acquisition of sexual weapons: (a) large and (b) small animals. It can be verified that the species is resilient and that its populations do not present great differences in its structure during hydric stress events. Futhermore, the reproductive aspects of M. amazonicum (fecundity, abortion and frequency of ovigerous females) are not significantly altered by the fluctuations of water levels and rainfall promoted by the climatic phenomenon "El niño". In some populations of this species, spores of the Inodosporus genus (Microsporidia) develop within the muscle fibers and promote the "color shrimp disease" by modifying the swimming and escape mechanism of the infected animals, making these shrimps more susceptible to predation. The evaluation of the histomorphological and population aspects analyzed in the different phenotypes allowed the understanding and comparison of bioecological and reproductive processes for the species. In addition, the gaps involving the phenotypic plasticity of populations of M. amazonicum were filled with the present study.
The Amazon river shrimp Macrobrachium amazonicum exhibits populations with great phenotypic plasticity and high morphological and reproductive variability. Three phenotypes are recorded for the species, through the evaluation of their life history, morphological and reproductive characteristics, being: (a) large amphidromous, and (b) large and (c) small hololimnetic animals. These characteristics allow these animals to occupy diverse aquatic environments in Brazil. In recent years, M. amazonicum records have increased significantly in continental freshwater environments in Brazil, mainly in reservoirs inserted at the Paraná Basin. However, information on bioecological and reproductive aspects in such environments is scarce. Also, there were no studies evaluating the histomorphology of the reproductive systems in Amazon shrimp. In addition, the phenotypic plasticity of populations of M. amazonicum is not yet fully understood. In the present thesis the histoanatomic patterns of the reproductive systems were analyzed in three phenotypes of the species. As well, the biology and ecology of populations with different phenotypes were investigated in reservoirs of the southeastern Brazil. In addition, the first record of intersexuality and microsporidiosis in the species are presented here. Regardless of the life history and sexual strategy adopted, all populations of M. amazonicum analyzed present similar anatomical, histological, histochemical and ultrastructural patterns in their reproductive systems. However, females and males of the small populations tend to invest more energy in reproductive aspects when compared to large amphidromous and hololimnetic animals. Small females displace more energy to produce larger oocytes/eggs and lipid reserves for larvae, while males of this phenotype invest energy in sperm production and concentration in the detriment of the acquisition of sexual weapons. Intersexuality in the species is a rare phenomenon (0.06%) associated with hormonal disruption and/or genetic mutation. In neotropical reservoirs the hololimnetic populations of M. amazonicum presents two phenotypes, defined by the acquisition of sexual weapons: (a) large and (b) small animals. It can be verified that the species is resilient and that its populations do not present great differences in its structure during hydric stress events. Futhermore, the reproductive aspects of M. amazonicum (fecundity, abortion and frequency of ovigerous females) are not significantly altered by the fluctuations of water levels and rainfall promoted by the climatic phenomenon "El niño". In some populations of this species, spores of the Inodosporus genus (Microsporidia) develop within the muscle fibers and promote the "color shrimp disease" by modifying the swimming and escape mechanism of the infected animals, making these shrimps more susceptible to predation. The evaluation of the histomorphological and population aspects analyzed in the different phenotypes allowed the understanding and comparison of bioecological and reproductive processes for the species. In addition, the gaps involving the phenotypic plasticity of populations of M. amazonicum were filled with the present study.
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Palavras-chave
camarão amazônico, fenótipos, sistemas reprodutores, ambientes lênticos, Caridea, Amazon river shrimp, phenotypes, reproductive systems, lentic environments