Parasitismo por Neoechinorhynchus buttnerae (Golvan, 1956) em Colossoma macropomum (Cuvier, 1818): caracterização hematológica, bioquímica e histopatológica

Abstract

The present work evaluated the impact of parasitism on hematological and biochemical parameters in the rearing of tambaqui (Colossoma macropomum) and tissue damage caused by Acanthocephala infection Neoechinorhynchus buttnerae. To reach these objectives a total of 42 tambaqui specimens were collected in commercial fish culture. Of these, 32 fish were used to identify the metazoan parasites and characterization of the hematological and biochemical profile; While 10 specimens (5 parasitized and 5 non-parasitized) were used for the application of stereological techniques in the morphometric investigation of the changes caused by the presence of acanthocephals (N. buttnerae) in the intestine of tambaqui (Colossoma macropomum). Of the analyzed fish, 100% were parasitized, being 100% by Monogenea helminths and acantocephalans, 59.38% by copepod crustaceans and 53.13% by branchiura. The highest mean intensity was of Acanthocephala, followed by monogenetic, copepods and branchiura. The species of helminths identified were: Anacanthorus spathulatus, Mymarothecium boegeri and Notozothecium janauachensis (Monogenea) and Neoechinorhynchus buttnerae (Acanthocephala). There was a significant positive correlation between fish weight and hematocrit (Ht), hemoglobin (Hb), mean corpuscular volume (MCV), mean corpuscular hemoglobin (HCM), as well as between total length and MCV, HCM. For the condition factor, as well as Ht and Hb a negative correlation with Copepoda parasites was observed. There was a significant negative correlation between Acanthocephala and the parameters Ht, Hb, thrombocytes and glucose, as well as between Monogenea and glucose, indicating that the hemogram could be influenced by endogenous factors such as length and body weight of the fish, as well as by parasitism, affecting the health status of tambaquis. Regarding the evaluation of the tissue damage, using a stereological tool, the portions of the intestine were classified into 7 regions, according to how the loops are naturally loosened in the coelomic cavity. As regards the mean volume of the intestinal layers (mucosa, submucosa, muscular and serous), the increase in mucosa volume was statistically significant in regions 3, 4 and 5. In these regions, the average parasitic load was approximately 34 parasites / region. In the evaluation of the intestinal layers of tambaqui, the mucosa layer was the most affected by the presence of acanthocephala, and a significant difference could be observed between all regions analyzed in the comparison of parasitized and non-parasitized groups, while the submucosa presented significant leukocytes infiltrate in regions 2, 3 and 4 in the parasitized fish. The muscular showed leukocytes infiltrate in regions 2, 3 and 5 of the parasitized group. There was relevant muscular edema only in regions 2 and 5 of the parasitized group. It should be noted that the surface area of the mucosa was not altered in the parasitized fish, suggesting that the absorption at the villi level was not altered. Therefore, the tambaquis evaluated presented moderate infestation by metazoan parasites, capable of weakening the hosts as observed through hematological and biochemical alterations; it is further added that the intestinal mucosa layer of tambaqui was affected by the presence of N. buttnerae, and that despite the damage observed the surface area of the mucosa, the main site of nutrient absorption, was preserved.