Acute toxicity assessment of arsenic, chromium and almix 20WP in Euphlyctis cyanophlyctis tadpoles.

Abstract

Heavy metals and herbicide are gaining serious environmental concern in aquatic toxicology due to its adverse effects on aquatic organisms especially amphibians. Accordingly, present study first time evaluated the acute toxicity of two heavy metals [arsenic (As3+) and chromium (Cr6+)] and a herbicide (Almix) to Indian skittering frog tadpole, Euphlyctis cyanophlyctis. The LC50 values of As, Cr and Almix for 24, 48, 72 and 96h were 73.58, 56.31, 43.58 and 32.58mgL-1; 326.68, 224.31, 171.92 and 141.99mgL-1; and 1297.85, 1148.22, 1033.62 and 955.17mgL-1, respectively. It also revealed the concentration- and time-dependent increased mortality rate under these toxicants. The safety concentrations (SC) of As, Cr and Almix to tadpoles were 3.26, 14.20 and 95.52mgL-1, respectively. The findings disclosed that As is highly toxic to E. cyanophlyctis than Cr and Almix. Alkaline phosphatase (ALP) activity showed varied responses to exposed chemicals. In particularly, ALP activity reduced significantly for Cr treatment. Glutathione S-transferase (GST) activity in E. cyanophlyctis was significantly inhibited by As treatment (p<0.05); however, GST activity was remain unchanged for Cr and Almix (p>0.05). The As toxicity correlates positively with GST inhibition (r=0.779, p<0.01); contrarily, Cr and Almix revealed negative correlation with GST induction (r=-0.461 and -0.19, respectively; p>0.05). This result indicated that GST play a crucial role for regulating the tadpole mortality and intoxication by As, Cr and Almix. Overall, our findings demonstrate the different levels of toxic sensitivity (adverse effects) under different toxicants on E. cyanophlyctis tadpoles. Finally, the present findings could be used as baseline information of toxicosis for metalloid, heavy metal and herbicide exposures in wild frog populations.