Acute toxicity of three antifungal chemicals on silverside Odontesthes bonariensis (Valenciennes 1835) eggs

Abstract

The effects of sodium chloride (NaCl) and formalin (F) on some toxicological parameters and the hatching rate of Odontesthes bonariensis eggs were examined under laboratory conditions, and the determined values were compared with those obtained for Malachite Green (MG), which was used as a reference toxic. The 96 hours nominal LC 50 were 1.51 mg L −1 , 652.14 µl L −1 and 34.82 g L −1 for MG, F and NaCl, respectively. The No-Observed-Effect Concentration (NOEC) and the No-Effect Concentrations (NEC) were 1.5 mg L −1 and 0.507 mg L −1 (MG), 400 µl L −1 and 530 µl L −1 (F) and 30.0 g L −1 and 28.68 g L −1 (NaCl), respectively. Hatching rates of 60% or higher were determined for eggs after 168 hours incubation in the assayed solutions at concentrations of 0.75 mg L −1 (MG), 300 µ L −1 (F) and 20 g L −1 (NaCl); at higher concentrations the hatching rates were severely affected.

Pathogenic ability and saline stress tolerance of two Fusarium isolates from Odontesthes bonariensis eggs

“…A decrease in the mortality by the fungal infection was observed when increasing the NaCl concentration, until the mortality observed was only due to a deleterious effect by NaCl on eggs in concentrations up 20 g/l; similar findings were reported by Pacheco Marino and Salibián. 31 Many fungi isolated from extreme environments possess diverse mechanisms that allow them to counterbalance the effects of NaCl and other salts, though their growth may also be reduced when the salt concentration in the medium increases, reason why the NaCl may be applied as a fungistatic agent. 3,47 Deleterious effects of the increase in the salinity can have a direct response in mycelia, causing osmotic stress or acting as a toxic component interfering with membrane stability and/or enzymatic activity.…”

Efeito in vitro de químicos no crescimento micelial de Saprolegnia spp.

“…Após a homogenização e solidificação do agar, um disco de 9mm de diâmetro do cultivo do oomiceto foi semeado na posição central da placa e incubada em estufa bacteriológica a 25°C, durante quatro dias. (PACHECO-MARINO & SALIBIAN, 2010). Dessa forma, os resultados in vitro obtidos no presente estudo sugerem que o formaldeído pode ser empregado em baixas concentrações para o controle de saprolegniose em peixe-rei.…”