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Resumo -O objetivo deste trabalho foi avaliar a tolerância de juvenis de pirarucu, Arapaima gigas, a concentrações crescentes de amônia na água. Oito peixes (2,6±0,4 kg e 70,5±4,1 cm de comprimento) foram distribuídos aleatoriamente em quatro tanques (0,8x0,9x2,6 m) com 410 L de água tamponada com Na 2 PO 4 e HCl, ambos a 0,1 M, onde ficaram por 33 dias. As concentrações de amônia no plasma sanguíneo dos peixes e na água foram determinadas pelo método do salicilato. A glicose plasmática e os níveis de amônia aumentaram proporcionalmente à concentração de amônia na água. Juvenis de pirarucu toleram altas concentrações de amônia na água.Termos para indexação: Arapaima gigas, fisiologia de peixes, piscicultura. Tolerance of pirarucu juveniles to increasing ammonia concentration in a closed environmentAbstract -The objective of this work was to evaluate the tolerance of pirarucu (Arapaima gigas) juveniles to increasing concentrations of ammonia in the water. Eight fish (2.6±0.4 kg and 70.5±4.1 cm length) were evenly distributed in four tanks (0.8x0.9x2.6 m) with 410 L of water buffered with Na 2 PO 4 (0.1 M) and HCl (0.1 M), where they were kept for 33 days. Ammonia concentrations in the fish blood plasma and in the water were determined by the salicilate method. Plasma glucose and ammonia levels increased proportionally to the concentration of ammonia in the water. Pirarucu juveniles tolerate high concentrations of ammonia in the water.

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This study evaluated the in vitro and in vivo antiparasitic efficacy of formalin against Dawestrema cycloancistrium, the effects on the physiological response of Arapaima gigas and the residual action on fish muscle after 96 h of exposure. As regards the in vitro assay, 0, 22, 44, 66, 88, 110, 330, 660 and 880 mg L − 1 formalin were tested. After 1 h of exposure to 660 and 880 mg L − 1 formalin, there was a 100% mortality of D. cycloancistrium as well as after 2 h of exposure at 330 and 110 mg L − 1 and 3 h of exposure at 44, 66 and 88 mg L − 1. Concerning the in vivo test, when fish were exposed to formalin at 0, 220, 330, 440 and 550 mg L − 1 , there was 100% survival at all concentrations and exposure times evaluated. Baths of 1 h with 440 and 550 mg L − 1 formalin showed 93.3% and 99.3% efficacy respectively. However, the baths of 12 h with 55 and 66 mg L − 1 formalin had the efficacy of 44.5% and 55.5% respectively. In 1 h baths with 220, 330, 440 and 550 mg L − 1 formalin, hematocrit, hemoglobin, number of total erythrocytes, mean corpuscular volume, mean corpuscular hemoglobin concentration, mean corpuscular hemoglobin, plasma glucose levels, cortisol, total proteins, chloride, calcium, sodium, potassium and magnesium of the fish presented no differences in relation to the control values. However, in baths of 12 h with 33, 44, 55 and 66 mg L − 1 formalin, there was a decrease in hematocrit, plasma levels of calcium and chloride, and increased levels of glucose and cortisol, depending on the concentration of formalin used. In the fish muscle, the formalin residue decreased after 96 h in all concentrations and periods evaluated, returning to values close to the control ones. The results indicate that formalin had its efficacy successfully proved in the treatment against D. cycloancistrium at higher concentrations such as 440 and 550 mg L − 1 formalin and shorter exposure time (1 h) without compromising fish homeostasis and consumer food safety. Statement of relevance: The manuscript represents original research on use of formalin in vitro and in vivo for treating infection by monogenoidean Dawestrema cycloancistrium in Arapaima gigas, the giant fish from Amazon. In the fish, muscle the residue levels of formalin after exposure was also investigated. Formalin have efficacy in the treatment against D. cycloancistrium at higher concentrations (440 and 550 mg.L − 1) of formalin and shorter exposure time (1 h) and without compromising A. gigas homeostasis and consumer food safety.

Perulernaea gamitanae (Copepoda: Lernaeidae) parasitizing tambaqui (Colossoma macropomum) (Characidae) and the hybrids tambacu and tambatinga, cultured in northern Brazil [Perulernaea gamitanae (Copepoda: Lernaeidae) ABSTRACTThe infestation rate in Colossoma macropomum, hybrid tambacu (C. macropomum x Piaractus mesopotamicus) and hybrid tambatinga (C. macropomum x Piaractus brachypomum) with Perulernaea gamitanae Thatcher and Paredes, 1985 from two fish farms in Amapá State, Brazil was studied. Lernaeid parasites (n=2887) were collected mainly on the tongue and the mouth cavity and also on cartilage of gill arches and filaments. Inflammation and fibrous nodules were observed on the attachment sites of the parasites. The infestation rate varied according to the fish farm and host. The prevalence of P. gamitanae was of 100% in hosts from one fish farm and was lower in the other fish farm. Higher intensity of P. gamitanae occurred in hybrids tambacu and tambatinga, but despite the high prevalence its intensity was moderate. This is the first report on epidemiology of P. gamitanae in cultured fishes from Brazilian Amazonia, and the occurrence of this crustacean parasite in two new hosts, the hybrids tambacu and tambatinga.Keywords: freshwater fish, Amazonia, crustacean, infestation, parasite RESUMO Estudou-se as taxas de infestação pelo crustáceo