Asian Fisheries Science 19(2006):131-139 131 -----Un-corrected proof --- Do not cite--- Asian Fisheries Society, Manila, Philippines Available online at www.asianfisheriessociety.org Physiological Changes in Indian River Prawn Macrobrachium malcolmsonii Experimentally Infected with Vibrio alginolyticus and Vibrio anguillarum SATYANARAYAN SETHI 1 , SUBHASH CHANDRA MUKHERJEE 2 , BASANTA KUMAR DAS 1* , SURYA KANTA SAMAL 1 and SHALINI SONI 1 1 Central Institute of Freshwater Aquaculture (CIFA), Kausalyaganga, Bhubaneswar-751002, Orissa, India 2 Central Institute of Fisheries Education, Seven Bunglows, Versova, Mumbai-4000061, India Abstract Outbreak of diseases and health related problems due to vibriosis are common in brackishwater aqua- culture and mariculture. However, studies on vibriosis in the fresh water prawn are not well documented. In the present study, biochemical changes under induced stress condition in Indian river prawn Macrobrachium mal- colmsonii was studied. Prawn juveniles of (90 ± 5 mm) procured from a nearby river were injected with patho- genic bacteria (Vibrio alginolyticus and V. anguillarum) through the gill 0.3x10 6 cfu of each prawn for a period of 15 days in controlled laboratory environment. Total protein of the haemolymph decreased. Haemolymph cholesterol was elevated significantly (p ≤ 0.05) in V. anguillarum infection, whereas triglyceride and glucose level decreased in comparison to the control. Variation of aspartate amino transferase and alanine amino trans- ferase activities increased under bacterial stress condition. The acid phosphatase level was reduced and alkaline phosphatase activity increased. There was a decrease in bactericidal activity in infected prawns. Introduction Exposure of aquatic organisms to even very low levels of pollutants in their environ- ment may result in various physiological alterations in vital tissues. The immune response of prawns is affected by environmental factors, particularly chemical contaminants in water, and exposure to bacterial, viral and parasitic infections (Adams 1991). Survival rates from cul- tured shellfish are not always predictable, and mortalities associated with bacterial infection are common. Vibriosis is considered as one of the most serious disease problems in the prawn industry in the world and therefore, Vibrio alginolyticus and Vibrio anguillarum were chosen as bacterial challenge. Several studies have been conducted on vibriosis of kuruma shrimp, * Corresponding author. Tel.: +674 246 5446 * 228 / 235 (O), Fax: +674 246 5407 E-mail address: basantadas@yahoo.com