This study aimed to determine the lethal concentration and the structural and ultra-structural effects caused by the formalin exposure on juveniles of Arapaima gigas. Ninety fish (60.1± 2.5g and 20.2±0.9cm) were exposed to 0, 22, 44, 66, 88 and 110mg L-1 in order to determine the lethal concentration (LC50-96h) that was 36.4mg L-1 of formalin. Sublethal effects were evaluated using histopathological analysis on the gills and assessment of behavioral alterations and clinical signs. The LC50 of formalin for 24, 48 and 72h was 88.3, 64.7 and 56.8mg L-1 respectively. Clinical signs and behavioral changes were found: erratic swimming, lethargy, crowding on the water surface, loss of hydrodynamic equilibrium, spasms and agonistic confrontation, which were observed only at 88 and 110mg L-1. The histological alteration index (HAI) showed that 66, 88 and 100mg L-1 presented significant difference (p<0.05) in relation to unexposed fish, indicating that moderate damage to the gills of fish exposed to formalin had occurred. The mean values of alteration (MVA) for 22, 44, 66, 88 and 110mg L-1 were 1.14, 1.29, 1.51, 1.53 and 1.60 respectively, and differences in this index were only observed with 110 mgL-1 of formalin. It is therefore possible to conclude that sublethal concentrations of formalin (22.0mg L-1) did not compromise the health of juveniles of A. gigas. Finally, concentrations greater than to LC50-96h may be carefully used for short-term exposure, since the MVA for all concentrations tested only indicated localized lesions that did not compromise gills functionality of exposed fish.

No abstract

The aim of the present study was to assess the use of sodium chloride (NaCl) against monogenoid infestations in pirarucu (Arapaima gigas). Two assays were conducted with pirarucu juveniles, the rst comprising an in vitro exposure to 8; 9; 10 and 11 g.L − 1 NaCl and comparison to controls not exposed to NaCl, and the second, an in vivo exposure to NaCl at the same concentrations applied in the in vitro exposure. The best in vitro results were observed for one hour exposures at 9, 10 and 11 g.L − 1 NaCl, resulting in 60% and 100% parasite mortality, respectively. In vivo exposures to 8 and 10 g.L − 1 NaCl were 36 and 22% e cient, respectively, following two hours of exposure, with no mortality. Some dosedependent changes were observed in exposed sh, such as decreased hemoglobin and HCM values at the highest NaCl concentration compared to the other NaCl concentrations and the control group. More frequent gill tissue alterations were observed compared to the control group at the highest NaCl concentrations (10 and 11 g.L − 1 ). Decreased mean (p < 0.05) water pH values and increased mean electrical conductivity were noted compared to the control group. Our ndings suggest that NaCl exhibits low toxicity towards pirarucu and anthelmintic activity to the monogenoid Dawestrema cycloancistrium, directly in uenced by exposure time and concentration.

No abstract

This study evaluated the dietary inclusion of a fish protein hydrolyzate (FPH) derived from tilapia trimmings on physiological and growth parameters of juveniles of Arapaima gigas. A total of 180 arapaima juveniles (91.4 ± 2.7 g) were used in a complete randomized design with six treatments (n = 3). Fish were fed to apparent satiation four times a day for eight weeks, with diets containing increasing inclusion levels of FPH (0, 4, 8, 12, 16 and 20%). FPH diets did not affect growth and hemato-biochemical parameters of arapaima juveniles. The FPH from tilapia trimmings seems to be a suitable ingredient for arapaima over 90 g, feeds at least up to 20% inclusion level. No bioactive effects of the FPH could be detected.

No abstract

The aim of the present study was to assess the use of sodium chloride (NaCl) against monogenoid infestations in pirarucu (Arapaima gigas). Two assays were conducted with pirarucu juveniles, the first comprising an in vitro exposure to 8; 9; 10 and 11 g.L− 1 NaCl and comparison to controls not exposed to NaCl, and the second, an in vivo exposure to NaCl at the same concentrations applied in the in vitro exposure. The best in vitro results were observed for one hour exposures at 9, 10 and 11 g.L− 1 NaCl, resulting in 60% and 100% parasite mortality, respectively. In vivo exposures to 8 and 10 g.L− 1 NaCl were 36 and 22% efficient, respectively, following two hours of exposure, with no mortality. Some dose-dependent changes were observed in exposed fish, such as decreased hemoglobin and HCM values at the highest NaCl concentration compared to the other NaCl concentrations and the control group. More frequent gill tissue alterations were observed compared to the control group at the highest NaCl concentrations (10 and 11 g.L− 1). Decreased mean (p < 0.05) water pH values and increased mean electrical conductivity were noted compared to the control group. Our findings suggest that NaCl exhibits low toxicity towards pirarucu and anthelmintic activity to the monogenoid Dawestrema cycloancistrium, directly influenced by exposure time and concentration.