Aspectos alimentares e do parasitismo em podocnemis expansa de ambiente natural e criatório comercial no estado do Tocantins

Abstract

Podocnemis expansa has been suffering great pressure entropy on its populations. Wherever they exist they are usually part of human diet, frequently being consumed and having a cultural and economic value, especially in areas in Amazon. Protection programs and later the building up of creation farms have been established replenishing natural stocks. The studies in natural environment the species still has many blank areas, making it necessary to amplify the information which is still inexact in some specific areas. The objective of this study is to evaluate aspects to the feeding, such as their diet and its level of protein and parasitism in P. expansa, in captivity and in natural environment, associating such factors with the animal interaction and the interaction with their own habitat, in order to help the biological understanding, behavior and strategies to conserve and manage. The study was made with young subjects of the P. expansa, species with a shell length variation of 15 to 30cm. 80 Animals were captured in the wild over Javaés/TO river, parallels 9º53’22.20S” and 10º2’30.36S”, meridians 50º8’55.70W” and 50º0’39.66W”, they were then divided in groups of 20 individuals, the capturing being made in two times of the year, both in the dry and rain season. The animals were captured with hook without barb, net or diving. 100 hatchlings were transferred to captivity and evaluated in groups of 20 at each turn chosen in an aleatory form. At the State sponsored creation farm, Fazenda Praia Alta, county of Lagoa da Confusão/TO , coordinates 10º43’24.1S” and 49º50’40.9W”, 160 animals were evaluated in two distinct tanks, being 20 animals collected at each turn. The animals were submitted to gauging and calibration of the corporeal mass and biometrics measurements, ectoparasitism evaluations and blood collection for blood rubbing and haemoparasites check. Animals from the wild had the stomach content retrieved for diet evaluation, protein measurement of the food and gastric parasites. The analyses and diversity showed on the statistic and unfolded the interaction between the variable, on Tuckey and Mann-Withney tests and simple correlation. Diet on captivity was verified over food offering. in natural environment, analyzed for methods of gravimetrical occurrence and. The protein level was gotten by the table of composition of foods and through the Kjedal method of nitrogen determination. Results revealed low development on the older animals and the younger animals had a better growth. Diet based upon four types of vegetables with a protein content of approximated 0,51 and 7,81% and commercial fish food with a level of 24 and 28% of protein. In the wild their diet is mostly herbivorous, however younger animals show an increase relative in contents of animal origin. The quantity of stomach content differs statistically between the dry season and the rain season in about 5% from the dry season to the others. Variation on the level of protein changed from 0,226 to 12,5%. Parasitism in the wild showed 99% of infection by protozoan, with high level of parasitism, 31% by Nematoda and Platyhelmintes, corresponding from 1,24% to 95,34% of the stomach content, and 19% of ectoparasites, basically appearing during the dry season when the animals were on the flats. P. expansa showed it self on the wild as a host of parasites, without showing any signs of loosing any vital signs or debilitation. In captivity the results were, for the tanks, 20% and 46% of infection by protozoan, 45% and 6% by ectoparasite. The hatchlings newly born did not show any sign of being infected during this research. Among the Platyhelmintes are Halltrema avitellina (trematode digenetic), with higher frequency during the dry season and two species of monogenius. The nematodes are Klossinemella concilliatus, Atractis cruciata e Atractis sp (nematodeos), having higher frequency during the rain season. It was found gametocyte of Haemogregarina sp and within the erythrocyte inclusions unknown, having a higher frequency on the wild. There wasn’t correlation between U. expansa and Haemogregarina sp. The result of the parasitism goes against the hypothesis of the higher susceptibility of thecaptivity animals and reinforces the theses of the life time of the parasites. At ectoparasitism, the captivity conditions are favorable. The relations with the parasites might be of commensalisms, opportunism or real parasitism.