BIOLOGIA (PAKISTAN) PKISSN 0006 – 3096 (Print) June, 2016, 62 (1), 139-144 ISSN 2313 – 206X (On-Line) Author’s Contribution: A.K., Experimental design and manuscript writing; N.A., Experimental setup and laboratory work; W.A., Helped in manuscript writing. *Corresponding author:phd_asma@yahoo.com Histopathological Changes in Spleen and Kidney of Silver carp (Hypophthalmicthys molitrix) after Acute Exposure to Deltamethrin *ASMA KARIM, NOREEN AHMAD & WAJID ALI Department of Zoology, Govt: College of Science, Wahdat Road, Lahore. Pakistan. ABSTRACT The pyrethroid group of pesticides, which include deltamethrin, is preferably used for pest control programs as a replacement for organochlorines and organophosphates group of pesticides, as it has comparatively low toxicity and has low persistence in the environment. Deltamethrin is highly toxic to aquatic organisms including fishes as compared to terrestrial animals. The present study was carried out to explore the lethal effects of deltamethrin on spleen and kidney of silver carp. Numerous histological changes were observed in kidney and spleen of fish after acute exposure to pesticide. Doses were 25%, 50% and 75% of LC50. Histopathological changes like damage in tissues of spleen and kidney became severe with increasing dose concentration. Most pronounced histopathological changes in kidney included degeneration of renal tubules, dilatation of glomerular capillaries, degeneration of glomeruli, narrowing of the tubular lumen, and atrophy and lyses of glomerular tufts. Spleen of treated fish showed necrosis and significant changes in number of melano- macrophage centres as compared to control. Key Words: Deltamethrin, Silver carp, Degenerative changes, Kidney, Spleen INTRODUCTION Pesticides are substances or mixture of substances used to kill and destroy different pests. Pesticides contribute significantly to human welfare and at the same time they also have significant undesirable effects on non-target organisms (John., 2007; Hazarik & Das., 1998). There is a direct way of entry of Pesticides into the water when applied incorrectly, or by running off from surrounding treated products in an indirect way (Svobodova et al., 2003). Pesticides which have tendency to persist in the environment for a long time, produce a risk to fish and its consumers. The increase and persistence of insecticides in the aquatic environment add up to threat biological life, as acute and chronic poisoning in many aquatic organisms including fishes have been observed (Soderlund et al., 2002). The pyrethroid group of pesticides, including deltamethrin, is considered as a preferable replacement for organochlorines and organophosphates as former group has low toxicity and less persistence in the environment (Kamal & Khalid, 2012). It is a natural compound pyrethrum characterized as non persistent sodium channel modulator, and is much less acutely toxic than organophosphate and carbamate usually applied against household pests (Anderson, 1989; Class et al., 2012). The pyrethroids are extensively used as pesticides because they degrade shortly after their application, and lack the accumulation tendency in organisms (Laskowski., 2002). The major advantages of pyrethroids over organophosphrus pesticides are that these are very effective even in low concentration and stable in light and above all they disintegrate very easily. These pesticides have very low toxicity for birds and mammals (Koprucu & Aydin., 2004). Water is polluted by pesticides mainly due to rigorous agriculture along with surface run off and surface seepage after its application (Banaee et al., 2011). Contamination of surface waters in agriculture by pesticides is a global issue (Hill, 1985; Sibley & Kaushik, 1991). Pesticides pose a threat to human life and aquatic animals when their degraded parts are found in drinking water. Keeping these facts in view pesticides are well documented globally and form major issues at local, regional, national and global levels (Cerejeira et al., 2003; Spalding et al., 2003). Being aquatic vertebrates fishes are mainly susceptible to environmental