FAUNA DE HELMINTOS DE JUVENIS DE PIRARUCU, Arapaima gigas (SCHINZ, 1822) E ASPECTOS DE SUA PRODUCAO NO MUNICIPIO DE MANACAPURU AM

RESUMO

Na America do Sul, o Brasil destaca-se com o maior produtor de peixes agua doce e reune condicoes favoraveis para tornar-se um dos maiores produtores de peixes do mundo. Um dos peixes nativos com potencial para piscicultura e o pirarucu (Arapaima gigas), desde que resolvidos os problemas na sua cadeia produtiva, nas areas de reproducao, nutricao e sanidade. A falta de um pacote tecnologico na producao da especie tem contribuido para baixa oferta de larvas e alevinos, alem da alta taxa de mortalidade causada principalmente por doencas parasitarias e bacterianas. Com isso, o objetivo do estudo foi caracterizar as criacoes de A. gigas, registrar as ocorrencias, identificar as especies e determinar os indices de infestacao/infeccao parasitaria (Capitulo I). Este estudo foi realizado em sete pisciculturas do municipio de Manacapuru Amazonas, e registrado informacoes sobre estrutura de criacao, area inundada, fonte de abastecimento de agua, manejo e alimentacao dos reprodutores, larvas e juvenis. Amostras de 10 peixes foram obtidas em cada piscicultura, totalizando 70 peixes. Cada amostra correspondeu a uma desova de A. gigas em cativeiro. Durante essas coletas foram registrados os parametros de qualidade de agua. Os peixes foram medidos e pesados para calculo da equacao peso-comprimento e fator de condicao. Apos esta etapa, os peixes foram analisados quanto a presenca de parasitos, e os especimes encontrados foram fixados em etanol 70% e identificados a posteriori. Apos quantificacao dos parasitos foram calculados os indices parasitarios. Nas pisciculturas a reproducao, alevinagem e recria de A. gigas eram realizadas em barragens e viveiros de terra, abastecidos com agua represada, poco artesiano ou rio. A maioria das pisciculturas estao voltadas a reproducao e recria, os reprodutores eram alimentados com peixes forrageiros vivos e os juvenis inicialmente com zooplancton natural, depois nauplios de artemia ate substituicao total por racao comercial em po. Os parametros de qualidade da agua ficaram dentro dos padroes para o cultivo de especies de peixes tropicais. O peso e comprimento dos peixes foram diferentes entre as pisciculturas (p<0,05) e o fator de condicao (Kn=1,2) indicou boas condicoes corporais dos peixes. A. gigas apresentou crescimento alometrico negativo (b<3), indicando crescimento maior em comprimento do que em peso. Dos 70 peixes examinados, 43 estavam parasitados. Foram coletados 133 parasitos e identificados monogenea e digenea e os generos Hysterothylacium sp., Procamallanus (Spirocamallanus) sp. (Nematoda), Neoechinorhynchus sp. e Polyacanthorhynchus sp. (Acanthocephala). A prevalencia various de 30 a 100% (media de 61,4%), a intensidade media de 1,0 a 8,1 (media de 3,1 ± 4,4) e a abundancia media de 0,3 a 5,7 (media de 1,9 ± 3,8). Os parasitos monogenea foram coletados nas branquias, digenea encistados na bexiga natatoria e as larvas de Procamallanus (Spirocamallanus) sp. no intestino, todos com baixos indices parasitarios. As larvas de Hysterothylacium sp. foram coletadas em todo o trato gastrointestinal de A. gigas, principalmente o mesenterio. Os especimes de Neoechinorhynchus sp. foram coletados no mesenterio, enquanto Polyacanthorhynchus sp. no intestino. Hysterothylacium sp. apresentou os maiores indices parasitarios, seguido por Neoechinorhynchus sp. A correlacao entre abundancia de parasitos e fator de consicao relativo dos peixes nao foi significativo (p > 0,05), mas as correlcaoes entre peso e comprimento e abundancia de parasitos foram significativas (p < 0,05). Destaca-se que a fauna parasitaria de juvenis de A. gigas e composta majoritariamente por especies de endohelmintos, pelo nematoide Hysterothylacium sp., patogenica e com potencial zoonotico e pelo acantocefalo Neoechinorhynchus sp. Em adicao, nesse estudo foi descrita uma nova especie do filo Acanthocephala, parasitando juvenis de A. gigas cultivados no estado do Amazonas (Capitulo II). A descricao da nova especie somente foi possivel porque todos os especimes de Neoechinorhynchus sp. foram encontrados na fase adulta. A nova especie distingue de todas as outras do genero por uma combinacao de caracteres incluindo tronco menor, espinhos anteriores menores nos machos, espinhos mediano e posterior do mesmo tamanho em ambos os sexos, duas vesiculas seminais abaixo do reservatorio de cimento e em posicao ventral. O local de fixacao desta especie difere de todas as outras especies de acantocefalos, no mesenterio. Esta e a primeira especie de Neoechinorhynchus descrita para uma especie de peixe da familia Arapaimidae e a decima especie do genero registrada no Brasil, e o nome Neoechinorhynchus arapaimensis e proposto. Como medidas de prevencao e controle de parasitoses e recomendavel desinfectar as estruturas de producao no final do ciclo produtivo, eliminar mcrofitas aquaticas, individualizar o abastecimento, instalar filtro ou tela no local de captacao de agua, realizar um rigoroso controle sanitario na reutilizacao da agua, monitorar a qualidade de agua, realizar avaliacao sanitaria dos peixes, adotar quarentena para peixes adquiridos em outras pisciculturas, ofertar uma dieta mista com peixes, racao e suplemento vitamincio e mineral, alimentar os peixes com zooplancton congelado, incluir na dieta aditivos imunoestimulantes, contactar tecnico especializado para diagnostico de doencas e medidas de controle, desinfetar utensilios e manter a assepsia dos funcionarios.

ABSTRACT

In South America, Brazil stands out as the largest producer of freshwater fish and gathers favorable conditions to become one of the largest fish producers in the world. One of the native fish with potential for fish farming is the pirarucu (Arapaima gigas), as long as the problems in its production chain, in the areas of reproduction, nutrition and health, are solved. The lack of a technological package in the production of the species has contributed to a low supply of larvae and fingerlings, in addition to the high mortality rate caused mainly by parasitic and bacterial diseases. With that, the objective of the study was to characterize the A. gigas creations, register the occurrences, identify the species and determine the infestation/parasitic infection rates (Chapter I). This study was carried out in seven fish farms in the municipality of Manacapuru Amazonas, and recorded information on the structure of rearing, flooded area, water supply source, management and feeding of breeders, larvae and juveniles. Samples of 10 fish were obtained from each fish farm, totaling 70 fish. Each sample corresponded to one spawn of A. gigas in captivity. During these collections, the water quality parameters were recorded. Fish were measured and weighed to calculate the weight-length equation and condition factor. After this step, the fish were analyzed for the presence of parasites, and the specimens found were fixed in 70% ethanol and identified a posteriori. After quantification of the parasites, the parasite indices were calculated. In fish farms, the reproduction, hatchery and rearing of A. gigas were carried out in dams and earthen ponds, supplied with dammed water, an artesian well or a river. Most of the fish farms are dedicated to reproduction and re-creation, the broodstocks were fed live forage fish and the juveniles initially with natural zooplankton, then brine shrimp nauplii until total replacement by powdered commercial feed. The water quality parameters were within the standards for the cultivation of tropical fish species. Fish weight and length were different between fish farms (p<0.05) and the condition factor (Kn=1.2) indicated good body condition of fish. A. gigas showed negative allometric growth (b<3), indicating greater growth in length than in weight. Of the 70 fish examined, 43 were parasitized. A total of 133 parasites were collected and monogenea and digenea were identified and the genera Hysterothylacium sp., Procamallanus (Spirocamallanus) sp. (Nematoda), Neoechinorhynchus sp. and Polyacanthorhynchus sp. (Acanthocephala). The prevalence varied from 30 to 100% (mean 61.4%), the mean intensity from 1.0 to 8.1 (mean 3.1 ± 4.4) and the mean abundance from 0.3 to 5. 7 (mean 1.9 ± 3.8). Monogenea parasites were collected in the gills, digenea encysted in the swim bladder and the larvae of Procamallanus (Spirocamallanus) sp. in the intestine, all with low parasitic indices. The larvae of Hysterothylacium sp. were collected from the entire gastrointestinal tract of A. gigas, mainly the mesentery. Specimens of Neoechinorhynchus sp. were collected from the mesentery, while Polyacanthorhynchus sp. in the intestine. Hysterothylacium sp. presented the highest parasitic indices, followed by Neoechinorhynchus sp. The correlation between parasite abundance and fish relative consition factor was not significant (p > 0.05), but correlations between weight and length and parasite abundance were significant (p < 0.05). It is noteworthy that the parasitic fauna of juveniles of A. gigas is mainly composed of species of endohelminths, the pathogenic nematode Hysterothylacium sp., with zoonotic potential, and the acanthocephalon Neoechinorhynchus sp. In addition, this study described a new species of the phylum Acanthocephala, parasitizing juveniles of A. gigas cultivated in the state of Amazonas (Chapter II). The description of the new species was only possible because all specimens of Neoechinorhynchus sp. were found in adulthood. The new species is distinguished from all others in the genus by a combination of characters including smaller trunk, smaller anterior spines in males, medial and posterior spines of the same size in both sexes, two seminal vesicles below the cement reservoir and in a ventral position. The attachment site of this species differs from all other acanthocephalic species in the mesentery. This is the first species of Neoechinorhynchus described for a fish species of the Arapaimidae family and the tenth species of the genus recorded in Brazil, and the name Neoechinorhynchus arapaimensis is proposed. As measures to prevent and control parasites, it is recommended to disinfect production structures at the end of the production cycle, eliminate aquatic microphytes, individualize the supply, install a filter or screen at the water collection site, carry out a strict sanitary control in the reuse of water , monitor water quality, carry out fish health assessment, adopt quarantine for fish acquired in other fish farms, offer a mixed diet with fish, feed and vitamin and mineral supplement, feed fish with frozen zooplankton, include immunostimulant additives in the diet, contact specialized technician for disease diagnosis and control measures, disinfecting utensils and keeping employees clean.