ABSTRACT
The effect of lead, a heavy metal, was found to have clastogenic effects on Clarias batrachus. Chromosomal studies on the fish indicated that the 2n numbers of chromosomes were 50 [18 metacentric, 20 submetacentric and 12 telocentric]. The effects of lead on the catfishes were investigated by constituting four different groups [n=16]. Group A: Control, Group B: 0.010 ppm of Pb [Treatment I], Group C: 0.025 ppm of Pb, [Treatment II], Group D: 0.050 ppm of Pb [Treatment III]. The exposure period was 24 hr, 48 hr and 72 hr for each group. Chromosomal aberrations were observed in the form of ring chromosomes, breakage of chromosomes, dicentric chromosomes and fragments of chromosomes. The highest percentage of metaphase spreads with chromosomal aberrations observed were 78.3 in Treatment I during 24 hr exposure of Pb. Chromosomal aberrations were highest in the form of ring type chromosomes [63.0%] in Treatment I during 48 hr exposure period. Breakage in chromosomes were maximum [57.1%] in Treatment II during 72 hr of exposure period. Maximum numbers of dicentric chromosomes [52.9%] were observed in Treatment I during 72 hr of lead exposure. Finally, the fragmented chromosomes were observed to the maximum [45.2%] after 24 hr of lead exposure in Treatment III. The studies indicated that exposure of lead at different concentrations causes clastogenic effects on the chromosomal complements of C. batrachus and the maximum abnormalities were manifestated in the form of ring chromosomes [63.0%]