MONITORING OF SUBLETHAL EFFECT OF CHROMIUM ON MELANOPHORES

Abstract

Some heavy metals are essential for normal physiological functioning of fish but become toxic when they accumulate in their body tissues and are not metabolized, dyes. Chromium is dangerous as it can accumulate in fish body as much as 4000 times greater than that of their surroundings. The present investigation deals with sublethal effects of chromium sulphate (10 ppm. 10% of 96 h LC50) on the melanophores of Catla catla was investigated to understand its toxicity on Melanophores morphology. Observed toxic pathological alterations include statistically significant variations in the number, size and shape of the Melanophores. Due to the lysis of the Melanophores, the melanin contents were poured into the surrounding matrix of the connective tissue, between 20 and 30 days of exposure. The chromium induced morphological changes in the melanophores protected the delicate epidermis from the toxic medium. In addition to the physiological colour changes, there was slow morphological colour changes by the gradual regeneration of the chromatophores. The density of chromatophores was maximum after 45 days. These generated pigment cells were smaller in size and more in number when compared with the normal melanophores. The study show that higher concentrations of metals in fish can alter its physiological functioning that could lead to high mortality and ultimately loss of indigenous fish biota.