Comparative analysis of organochlorine and organophosphate pesticides on the learning ability and sustained swimming capacity of a freshwater fish

The behavioural effect of short-term static exposure (120 hours) to organochlorine (Dicofol) and organophosphate (Methyl parathion) pesticides were recorded in Climbing Perch (Anabas testudineus), a freshwater fish. The behaviours analyzed included associative learning ability and sustained swimming capacity against water current. The learning task given to the fish was to associate the neutral stimulus (air bubble) with unconditioned stimulus (food) in a two-chambered aquarium with a gate on the partition wall. The test fish, starved for twenty four hours, had to cross the gate to reach the food provided in the side chamber.

The control fish were able to associate air bubbles with food and crossed the gate to reach the side chamber within ten trials. In contrast, the fish exposed to the organochlorine and organophosphate pesticides failed to associate the neutral stimulus with the food, or to learn the position of the gate, regardless of the chemical nature of the pesticide.

Endurance (reflected in the sustained swimming ability against water current) was tested in a specially designed apparatus that could generate constant and measurable water flow. Both pesticides considerably reduced the endurance of the fish. The results are discussed in the light of alteration in behaviour, and its influence on adaptive ability of an organism.