LAUSR

TCS [5-chloro-2-(2,4-dichlorophenoxy)phenol] caused a concentration dependent delay in embryonic development, delay and decline in hatching and reduction in length and weight of hatchlings along with an increase in abnormal/deformed embryos and larvae and percent mortality. These parameters varied in a species specific manner and increased with TCS residue in body. The 96 h LC50 values of TCS for Cyprinus carpio, Ctenopharyngodon idella, Labeo rohita and Cirrhinus mrigala were estimated at 0.315, 0.116, 0.096 and 0.131 mg/L, respectively. Hatching got delayed by 16.33 h for C. carpio (0.47 and 0.50 mg/L TCS) and C. idella (0.20 mg/L TCS) but by 18.07 h for L. rohita (0.15 mg/L TCS) and by 19.33 h for C. mrigala (0.18 mg/L TCS). Spine malformations, oedema (yolk sac and cardiac) and deflated swim bladder were present in 100% larvae of C. carpio, C. idella, L. rohita and C. mrigala at 0.30, 0.08, 0.13 and 0.14 mg/L TCS, respectively. TCS also caused hemorrhage (all but C. idella, only 3.33%), albinism and deformed caudal fin (C. idella), hypopigmentation and rupturing of yolk sac (C. mrigala), gas bubble disease (C. mrigala and L. rohita), fusion of eyes (C. carpio) and degeneration of digestive tract (L. rohita) in 10-40% hatchlings. Exposed hatchlings were very weak and paralyzed, could not swim and remained settled at the bottom of jars. Embryonic development was observed to be an early indicator of the toxicity of TCS as oedema and bubbles in yolk were observed in 40-100% embryos/hatchlings at 0.08 mg/L TCS while 100% mortality was observed between 0.15 and 0.50 mg/L TCS. L. rohita was most sensitive and C. carpio was least sensitive to the stress of TCS. Accumulation of TCS in the hatchlings (1/10 of TCS in water) after 96 h exposure hints that even small quantities of TCS may change species diversity in natural waters.