INCIDENCE OF MENTUM DEFORMITY OF CHIRONOMID LARVAE (DIPTERA: CHIRONOMIDAE) PREVALENT IN RICE AGROECOSYSTEM OF HOOGHLY DISTRICT, WEST BENGAL: A SIGN OF PESTICIDE INDUCED STRESS?

Abstract

The mouthpart deformities of Chironomus sp. (Diptera: Chironomidae) larvae, particularly in the mentum teeth, have been proposed as a bioindicator of sediment quality and environmental stress. Larvae of Chironomus sp. were collected from rice fields located at Rishra, Serampore and Khanakul (District- Hooghly, West Bengal, India). Physico-chemical parameters of water and sediment were recorded at each site. The agronomic practices revealed an excessive application of pesticides in the rice field for better yield. Field data exhibit high incidence that percentage of deformity in Rishra compared with Serampore and Khanakul. Laboratory experiments demonstrated a correlation between field concentration of pesticides and occurrence of deformed larvae. Among the various head capsules structures, deformity of the mentum was strongly reflective of pesticide induced environmental stress.