Evaluation of the acute toxicity of mahua oil cake aqueous extract and its effect on the behavioral responses of the freshwater grapsid crab, Varuna litterata (Fabricius, 1798).

Mortality and behavioral alterations are monitored as the sensitive endpoints in toxicological studies and may be applied as useful biomarkers to assess piscicidal pollution in aquatic environment. Present study assesses acute toxicity of the piscicide, mahua oil cake (MOC), and its effect on the behavioral responses of the freshwater grapsid crab, Varuna litterata, under laboratory conditions. To determine the LC50 values, a 4-day acute static renewal toxicity test was done where 10 adult male crabs (mean length 2.870 ± 0.379 cm; mean weight 9.891 ± 3.951 g) were exposed to different concentrations (1, 5, 10, 15, 20, 25, 30, 35 ppt) of MOC aqueous extract with a control at different exposure periods. The LC50 values are 19.109 ppt for 24 h, 16.052 ppt for 48 h, 11.827 ppt for 72 h, and 7.631 ppt for 96 h. The high LC50 values indicate less sensitivity of this crab to the MOC extract than other aquatic animals. MOC extract has toxic effect on the mouthparts activity, whirling motion of water current producing activity, froth releasing activity, aggregation, balance and coordination actions, medium escaping behavior, locomotor activity, and fecal matter excretion of this crab in different exposure periods. Behavioral responses such as froth releasing activity, aggregation, and medium escaping behavior can be used as biomarkers of MOC pollution in aquatic environment.