N Save Nature to Survive 9(3): 1117-1122, 2014 www.thebioscan.in 1117 INCIDENCE OF MENTUM DEFORMITY OF CHIRONOMID LARVAE (DIPTERA: CHIRONOMIDAE) PREVALENT IN RICE AGRO- ECOSYSTEM OF HOOGHLY DISTRICT, WEST BENGAL: A SIGN OF PESTICIDE INDUCED STRESS? DEBNARAYAN SAHA 1* AND ABHIJIT MAZUMDAR 2 1,2 Entomology Research Unit, Department of Zoology, The University of Burdwan, Burdwan - 713104, West Bengal, INDIA 1 Raja Rammohun Roy Mahavidyalaya, Radhanagar, Hooghly - 712 406, West Bengal, INDIA. e-mail: debnarayansaha@gmail.com INTRODUCTION Mouthparts deformity of Chironomid larvae represents more traditional and successful methods for biological assessment of water quality. The relationship between morphological deformities and the occurrence of heavy metals and pesticides within the sediment was reported by Hamilton and Sæther (1971). Bhattacharya et al., (1999) recorded high incidence of deformity of mouthparts of Chironomid larvae occurring within the river Damodar flowing through the industrial zone of West Bengal. Deformities could provide a useful tool for assessing aquatic pollution, specifically that relates to industrial wastes and agricultural runoff (Saha and Mazumdar, 2013 Wiederholm, 1984; Warwick, 1985; Janssens de Bisthoven et al., 1999; Vermeulen, 1995; Bhattacharya et al., 2005, MacDonald and Taylor, 2006 and Al-Shami et al., 2010). The occurrence of natural abnormalities must be considered when using chironomid mouthpart deformties as an index of environmental degradation (Bird, 1997). Efforts to demonstrate the relationship of deformity incidence in chironomid larvae with water and sediment quality have been made (Vermeulen, 1995). Hamalainen (1999) suggest that deformity incidence of chironomid larvae was a potential indicator of the impact of contaminants in aquatic systems. The application of chironomid deformities as bioindicators of pollution stress has been reviewed and shown primarily for bioassessment 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. KEYWORDS Chironomidae Mentum deformities Pesticide Sediment Rice fields Received on : 08.02.2014 Accepted on : 24.07.2014 *Corresponding author purposes (Midya et al., 2013, Bhaduri et al., 2011, Amiryan, 2010 and Rosenberg, 1992). In this context, many researchers have developed several indices deformity based on chironomid larval deformities to better understand the causes (Hamalainen, 1999). Chironomids are most important macroinvertebrates in rice agro-ecosystem, they are most widespread and often abundant group of insects in freshwater environments (Pinder, 1986). The members of genus Chironomus sp. is considered ecologically versatile due to colonizing ability in most varied conditions and increase response to organic enrichment (Stevens et al., 2006). Chironomids were considered as one of the most useful groups in assessing the quality of running waters because of their abundance, diversity and colonizing ability (Sæther, 1980). The chironomids have been recorded in rice fields throughout the world including India, Australia and the USA (Stevens et al., 2006). The rice field is a unique man-made environment with huge diversity of aquatic organisms and this diversity are closely related to the environmental changes of rice agro- ecosystem (Saha and Mazumdar, 2013 and Ali, 1996). Fernando (1993) reported that presently rice cultivation is highly mechanized and uses high fertilizer and pesticide for enhance production. Routine agricultural practices including ploughing, draining, fertilizer and pesticide applications and