MERCURY INTOXICATION IN GRASS CARP (CTENOPHARYNGODON IDELLA)
M. S.
Khan, S. A. Khan, Z.I. Chaudhary, M. N.
Khan,1 A.Aslam,
K.Ashraf2, R. M. Ayyub and M.
F.Rai
Department of Pathology1; Department of Fisheries and 2Department
of Parasitology,University
of
Veterinary
and Animal Sciences,
Lahore,
54000,
Pakistan
Abstract
The present project was carried out to
study the effects of acute and chronic mercury intoxication in Grass carp (Ctenopharyngodon
idella). For acute phase experiment, 48 fish were divided into four equal
groups (A, B, C and D). Groups B, C and D were given HgCl2 at
sublethal dose as 0.4, 0.5 and 0.6 mg/L, respectively, while group A acted as
control. Skin, gills and kidneys were isolated from the fish after 48 and 96
hours for pathological studies. For chronic phase, 72 fish were divided into
five groups (E, F, G, H and I), containing 12 fish each except group E which
contained 24 fish. Groups F, G, H and I were given HgCl2 at sublethal
dose of 0.3 mg/L for 4, 8, 12 and 16 days, respectively, while group E acted as
control. Skin, gills and kidneys were isolated from each group (F, G, H and I)
after 4, 8, 12 and 16 days respectively for pathological studies.During chronic phase in the treatment groups normal histology of
epidermis was disturbed with increased number of immature cells. Overall, skin
layers were atrophied and withered. Histopathology of gills showed hyperplasia
of epithelial cells of gill filaments, fusion of secondary lamellae giving a
club shaped appearance of filaments and contraction and sloughing of respiratory
epithelium in groups F, G, H and I. Histopathological examination of kidneys
also showed a wide range of toxicity lesions and destruction in treatment groups
(F, G, H and I).Disintegration and
disorganization of cells of both renal and haemopoitic systems including
dilatation of capillaries and thickening of basal lumen were observed. Mild to
sever tubular epithelial degeneration, karyolysis, dilation and shrinkage of
Bowman’s capsule and glomerulus were also observed. In chronic phase experiment,
fish showed clinical signs including restlessness, difficult breathing, fin
flickering and jerky movements. Suppressed growth rate was also observed in
treatment groups (F, G, H and I). During acute phase, after 48 hours, these
histopathological lesions were absent in all the groups in all the organs. But
after 96 hours, these respective lesions in respective organs were usually of
mild, moderate and severe nature in groups B, C and D, respectively. It was
concluded that mercury intoxication not only resulted in marked
histopathological changes and abnormal clinical signs but also depressed growth
rate of fish.