Dieta, aspectos metabólicos e parasitológicos de Oreochromis niloticus cultivados e silvestres, no reservatório de Ilha Solteira, rio Grande, SP
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Data
2019-02-22
Autores
Pagliarini, Cibele Diogo
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Universidade Estadual Paulista (Unesp)
Resumo
Oreochomis niloticus é uma espécie de peixe não-nativa invasora no Brasil, e atualmente, a mais produzida e consumida no país. Contudo, os efeitos/influências ambientais deste sistema de cultivo ainda não estão satisfatoriamente elucidados. Além disso, os escapes são problemas recorrentes nas estações de criação. Assim, o objetivo deste trabalho foi caracterizar a composição da dieta, fatores metabólicos musculares e aspectos parasitológicos de O. niloticus silvestres e cultivados, além de avaliar a sobreposição de nicho trófico desta espécie com a ictiofauna silvestres que habita o entorno dos tanques-rede em uma piscicultura no reservatório de Ilha Solteira, rio Grande, SP. Realizou-se duas coletas de O. niloticus e de outras 17 espécies silvestres, uma no mês de janeiro e outra em julho de 2017. Os espécimes foram eutanasiados, medidos (cm) e pesados (g). Em campo, realizou-se raspagem da pele de O. niloticus com lâminas histológicas para avaliar a presença de ectoparasitas. Todos os peixes foram necropsiados para retirada dos estômagos, fixados e analisados posteriormente. Apenas dos exemplares de O. niloticus foram retiradas amostras de tecido muscular para análises metabólicas e os demais órgãos para avaliação de endoparasitas. A carcaça foi filetada e o tecido muscular foi analisado em mesa de luz para inspeção macroscópica de parasitas encistados. Para todas as análises estatísticas foram consideradas a variação espaço/temporal [espaço (local) = exemplares oriundos dos tanques de cultivo e ambiente natural; temporal (estação) = seca e chuvosa]. A composição alimentar apresentou diferenças significativas quanto ao local e período de coleta. Oreochromis niloticus apresentou dieta ampla, variada e com alta dissimilaridade considerando o local, sendo a ração, o item com maior contribuição para tais diferenças. Sobreposições tróficas altas entre O. niloticus silvestres e outras espécies de peixes, inclusive nativas, foram observadas, demonstrando possível competição por recursos alimentares. Diferenças também foram encontradas para algumas variáveis metabólicas, porém, a maioria das concentrações foram semelhantes entre exemplares silvestres e cultivados, demonstrando a influência da piscicultura sob a estrutura trófica da ictiofauna, em especial, para espécies oportunistas e generalistas. Além disso, os peixes analisados apresentaram 11 táxons de parasitas, sendo que Enterogyrus spp., fases larvais de digenéticos e hirudíneos da família Glossiphoniidae ocorreram exclusivamente em espécimes de O. niloticus silvestres. Houve diferença estatística quanto à composição da comunidade parasitária, sendo a comunidade de O. niloticus silvestres mais diversa. Observou-se a associação epibiótica entre Dolops carvalhoi e Epistylis sp., sendo este o primeiro relato de epibiose entre essas espécies, as quais foram encontradas parasitando O. niloticus cultivados e silvestres no presente estudo. Oreochromis niloticus silvestres tendem a permanecer próximas aos tanques de cultivo, aproveitando-se de restos de ração, facilitando trocas e transmissões de parasitas. Ainda, a semelhança de concentração de substratos metabólicos dos filés dos espécimes avaliados evidencia a grande perda de ração para o ambiente, que em excesso, pode causar problemas ambientais, bem como favorecer a reprodução de algumas espécies de parasitas. Assim, o estudo dispõe de informações acerca da ecologia trófica de várias espécies, dados sobre metabolismo muscular da espécie mais cultivada e consumida no país, relação hospedeiro-parasita-ambiente, dispersão de agentes etiológicos e epidemiologia na aquicultura, que podem contribuir para um melhor ordenamento da atividade aquícola nacional.
Oreochomis niloticus is a non-native invasive fish in Brazil, and currently the most produced and consumed fish in the country. However, the environmental effects/influences of this production system are poorly elucidated. In addition, accidental releases are recurring problems in fish farms. Thus, the aims of this study were to characterize the composition of the diet, muscle metabolic factors and parasitological aspects of wild (from accidental release) and cultivated O. niloticus, besides evaluating the overlap of trophic niche of this species with the wild icthyofauna that inhabits the environment close to the cage fish farm in the Ilha Solteira reservoir, rio Grande, SP. Two samples of O. niloticus and 17 other wild species were taken, during the rainy period (in December 2016) and the dry period (in July 2017). The specimens were euthanized, measured (cm) and weighed (g). In the field, specimens of O. niloticus were submitted to skin scraping to collect the mucus on slides to evaluate the presence of ectoparasites. All fish were necropsied to remove the organs (stomach, intestine, liver, mesentery, kidney, eyes and heart) to parasitological procedures. The stomachs were fixed and the parasitological and diet analysis were performd concomitante.The muscles tissues of O. niloticus specimens were removed, and samples were used in the metabolic analysis, and a part of the material was filleted and submmited to a macroscopic inspection in the candling table, to looking for encisted endoparasites. . For all statistical analyzes we considered the space/time variation [space (local) = specimens from the cage fish farm and natural environment (wild); temporal (season) = dry and rainy]. The diet composition presented significant differences in relation to the local and season of the samples. Oreochromis niloticus presented a wide, varied diet with high dissimilarity considering the local, being the ration, the item with greater contribution to such differences. High trophic overlaps between wild O. niloticus and other species of fish, including native, were observed, demonstrating possible competition for food resources. Differences were also found for some metabolic variables, however, most concentrations were similar between wild and cultivated specimens, demonstrating the influence of fish farming in the trophic structure of the icthyofauna, especially for opportunistic and generalist species. In addition, the analyzed fish presented 11 taxa of parasites, and Enterogyrus spp., larval stages of digeneans and hirudineans (Glossiphoniidae) occurred exclusively in wild specimens of O. niloticus. There was a statistical difference regarding the composition of the parasite community, and the parasite community of wild O. niloticus was more diverse. The epibiotic association between Dolops carvalhoi and Epistylis sp. was observed, being this the first report of epibiosis among these species, which were found parasitizing cultivated and wild O. niloticus in the present study. Wild Oreochromis niloticus tend to remain close to the cages, utilizing leftover of ration coming from the fish farming, facilitating the share and transmissions of parasites. Also, the similarity of metabolic substrate concentration of the muscle tissues (fillets) of the evaluated specimens evidences the great loss of ration to the environment, which in excess, can cause environmental problems, as well as favor the proliferation of some parasites. Thus, the present study has information about the trophic ecology of several species, data on muscle metabolism of the most cultivated and consumed species in the country, host-parasite-environment relationship, dispersion of etiological agents and epidemiology in aquaculture, which may contribute to a better national aquaculture activity.
Oreochomis niloticus is a non-native invasive fish in Brazil, and currently the most produced and consumed fish in the country. However, the environmental effects/influences of this production system are poorly elucidated. In addition, accidental releases are recurring problems in fish farms. Thus, the aims of this study were to characterize the composition of the diet, muscle metabolic factors and parasitological aspects of wild (from accidental release) and cultivated O. niloticus, besides evaluating the overlap of trophic niche of this species with the wild icthyofauna that inhabits the environment close to the cage fish farm in the Ilha Solteira reservoir, rio Grande, SP. Two samples of O. niloticus and 17 other wild species were taken, during the rainy period (in December 2016) and the dry period (in July 2017). The specimens were euthanized, measured (cm) and weighed (g). In the field, specimens of O. niloticus were submitted to skin scraping to collect the mucus on slides to evaluate the presence of ectoparasites. All fish were necropsied to remove the organs (stomach, intestine, liver, mesentery, kidney, eyes and heart) to parasitological procedures. The stomachs were fixed and the parasitological and diet analysis were performd concomitante.The muscles tissues of O. niloticus specimens were removed, and samples were used in the metabolic analysis, and a part of the material was filleted and submmited to a macroscopic inspection in the candling table, to looking for encisted endoparasites. . For all statistical analyzes we considered the space/time variation [space (local) = specimens from the cage fish farm and natural environment (wild); temporal (season) = dry and rainy]. The diet composition presented significant differences in relation to the local and season of the samples. Oreochromis niloticus presented a wide, varied diet with high dissimilarity considering the local, being the ration, the item with greater contribution to such differences. High trophic overlaps between wild O. niloticus and other species of fish, including native, were observed, demonstrating possible competition for food resources. Differences were also found for some metabolic variables, however, most concentrations were similar between wild and cultivated specimens, demonstrating the influence of fish farming in the trophic structure of the icthyofauna, especially for opportunistic and generalist species. In addition, the analyzed fish presented 11 taxa of parasites, and Enterogyrus spp., larval stages of digeneans and hirudineans (Glossiphoniidae) occurred exclusively in wild specimens of O. niloticus. There was a statistical difference regarding the composition of the parasite community, and the parasite community of wild O. niloticus was more diverse. The epibiotic association between Dolops carvalhoi and Epistylis sp. was observed, being this the first report of epibiosis among these species, which were found parasitizing cultivated and wild O. niloticus in the present study. Wild Oreochromis niloticus tend to remain close to the cages, utilizing leftover of ration coming from the fish farming, facilitating the share and transmissions of parasites. Also, the similarity of metabolic substrate concentration of the muscle tissues (fillets) of the evaluated specimens evidences the great loss of ration to the environment, which in excess, can cause environmental problems, as well as favor the proliferation of some parasites. Thus, the present study has information about the trophic ecology of several species, data on muscle metabolism of the most cultivated and consumed species in the country, host-parasite-environment relationship, dispersion of etiological agents and epidemiology in aquaculture, which may contribute to a better national aquaculture activity.
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Palavras-chave
Tilápia do Nilo, Composição alimentar, Variáveis metabólicas, Parasitas, Piscicultura em tanques-rede, Nile Tilapia, Food composition, Metabolic variables, Parasites, Cage fish farm