Environmental Toxicology and Pharmacology 22 (2006) 200–204 Gill and kidney histopathology in the freshwater fish Cyprinus carpio after acute exposure to deltamethrin Elif Ipek Cengiz ∗ Department of Biology, Section of Hydrobiology, Faculty of Science and Art, University of Dicle, 21280-Diyarbakir, Turkey Received 15 December 2005; accepted 24 March 2006 Available online 23 May 2006 Abstract The histopathological effects of deltamethrin on the gill and kidney tissues of the common carp, Cyprinus carpio were determined by light microscopy. The fish were exposed to 0.029 mg l -1 (50% of 96 h LC 50 ) and 0.041 mg l -1 (70% of 96 h LC 50 ) solutions of deltamethrin for short-term (96 h). The most common gill changes at all doses of deltamethrin were desquamation and necrosis. Besides, aneurism in secondary lamellae, lifting of the lamellar epithelium, oedema, epithelial hyperplasia and fusion of the secondary lamellae were reported. Lesions in the kidney tissues of fish exposed to deltamethrin were characterized by degeneration in the epithelial cells of renal tubule, pycnotic nuclei in the hematopoietic tissue, dilation of glomerular capillaries, degeneration of glomerulus, intracytoplasmatic vacuoles in epithelial cells of renal tubules with hypertrophied cells and narrowing of the tubular lumen. © 2006 Elsevier B.V. All rights reserved. Keywords: Synthetic pyrethroids; Deltamethrin; Histopathology; Cyprinus carpio; Gill; Kidney 1. Introduction Pyrethroid insecticides are used preferably over organochlo- rine and organophosphates due to their potent insecticidal prop- erties and are practically non-toxic to most non-target animals, especially mammals. Pyrethroids have a short life in most ani- mals as they are readily metabolized; fish are an exception since they seem to be deficient in the enzyme system that hydrolyzes pyrethroids (Haya, 1989). Fish are among the group of non- target aquatic organisms. Pyrethroids pose a serious potential hazard to fish because of the use of these compounds in many aquatic larvicidial pro- grams (Tara and Glenn, 1986). Pyrethroids are highly toxic to most fish being deltamethrin one of the most toxic and widely used. The fish exhibit several symptoms of stress when treated with deltamethrin (Datta and Kaviraj, 2003). Emulsifiable con- centrate formulations of pyrethroids are usually two to nine times more toxic than the technical grade, most likely due to synergis- tic interactions (Sanchez-Fortun and Barahona, 2005). ∗ Tel.: +90 412 248 85 50/3197; fax: +90 412 461 38 99. E-mail address: ecengiz@dicle.edu.tr. Tissue damages brought about by waterborne pollutants can be easily observed because the fish gills come into immediate contact with the environment. The gill surface is more than half of the entire body surface area. In fish the internal environment is separated from the external environment by only a few microns of delicate gill epithelium and thus the branchial function is very sensitive to environmental contamination. Hence, fish serve as excellent bioassay animals for toxicological impact studies and have been widely used for this purpose. In fish, as in higher vertebrates, the kidney performs an important function related to electrolyte and water balance and the maintenance of a stable internal environment. The kidney excretes nitrogen-containing waste products from the metabolism such as ammonia, urea and creatinin. Following exposure of fish to toxic agents such as pesticides, tissue alter- ations have been found at the level of the tubular epithelium and glomerulus (Teh et al., 1997). Water pollution induces patholog- ical changes in fish. As an indicator of exposure to contaminants, histology represents a useful tool to assess the degree of pollu- tion. The common carp is an economically important fish and was selected for the bioassay experiments because of its widespread and presently cultured all over Asia, in most parts of Europe and on a small scale in some countries of Africa and Latin America 1382-6689/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.etap.2006.03.006