The Lethal Impacts of Roundup® (glyphosate) on the Fingerlings of Guppy, Poecilia reticulata Peters, 1859

Weedicides bring about adverse effects to non-targeted animal species in the agricultural fields and associated habitats. Among these, Roundup® (glyphosate) is one of the commonest that is used all over the world. The present laboratory investigation examined the effects of Roundup® on fingerlings of guppies (Poecilia reticulata). In this investigation, the 24-hr and 96-hr LC50 of Roundup® for the guppy fingerlings were determined by exposing them to a series of Roundup® test preparations ranging from 3.6 mg.L^-1 to 36 mg.L^-1. Further, the behavioural changes of the fingerlings at these test preparations were studied and the histopathological changes of their gills were examined. The results showed that the 24-hr and 96-hr LC50 for Roundup® were 15.1 mg.L^-1 and 9.76 mg.L^-1 respectively. These values are well below the recommended field concentration of Roundup®, which is 2,592 mg.L^-1. Fingerlings preferred to rest more at the surface of test preparations than resting elsewhere in the tanks. In contrast, such a behavioural change was not observed in the control. The histopathological study showed that the fingerlings exposed to all the Roundup® concentrations developed gill hyperplasia where its severity was concentration dependent. It is evident that the toxic concentration of Roundup® on guppy fingerlings is much lower than its recommended field concentration. At these toxic concentrations, Roundup® brings about stress and severe gill damage in guppies.