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Effect of Chromium, Cadmium and Mercury on the Gill Histology of Clarias Batrachus L.

SHAWKAT ARA BEGUM
Department of Zoology, University of Chittagong, Chittagong-4331, Bangladesh

BAHARUL HOQUE
Department of Zoology, University of Chittagong, Chittagong-4331, Bangladesh

QAMAR BANU
Department of Zoology, University of Chittagong, Chittagong-4331, Bangladesh

Abstract/ Executive Summary:

Effect of cadmium (Cd), chromium (Cr) and mercury (Hg) on the gill histology of Clarias batrachus L. was investigated following 28 days exposure to their sublethal concentrations under laboratory condition. Hyperplasia and hypertrophy of the lamellar epithelium, necrosis, partial lifting of epithelial layer, damage of gill ray, oedema of primary lamellae, damage of pillar cells and congestion of blood vessels were the main histopathological changes. In Cd treated fishes the interlamellar spaces were abolished but distended gill rays were characteristics of Cr treatment. Extensive cellular and tissue damages were prominent in Hg treated fishes.

Keywords: Heavy metal, Gill histology, Hyperplasia, Hypertrophy, Oedema

Location: Department of Zoology, University of Chittagong, Chittagong

Start Date:

End Date:

Program Area: Animal Health and Management

Commodity: Heavy metal

Objectives:

1. In the present work, effect of heavy metals Cd, Cr, and Hg on histology of the gill of Clarias batrachus L. was investegated following its exposure to sublethal concentrations for 28 days under laboratory condition.

Methodology:

Fresh and live specimens of Clarias batrachus L. (average length 16 ± 3 cm and weight 70 ± 5 g) was bought from Chittagong city market and acclimatized for 7 days in 25 L aquarium in tap water. Fish species were given oligochaetes, prawn and small pieces of Harpodon nehereus as food once in a day and water was changed at 24h interval. Following it, test fish specimens (20 / aquarium) were exposed to sub-lethal concentration of each heavy metal (Cd– 9 ppm, Cr– 12 ppm and Hg – 0.3 ppm) separately (treatment) for 28 days along with a control without heavy metal and fed once a day with a change of solution after each feeding. Standard method was followed for histopathological study. At the end of the exposure period gills from the metal exposed as well as control fishes were isolated, cleaned with physiological saline solution, cut into pieces and fixed in freshly prepared Bouin’s fixative. After 24 hours tissues were transferred to 70% alcohol for preservation. For histological slides preparation tissues were dehydrated in graded alcohol, cleared in benzene and embedded in paraffin. Thin sections (3-5µ) were cut by rotary microtome, double stained by eosin-haematoxylin, mounted with DPX for examination under microscope. Photomicrographs were taken by Ricoh 35 mm SLR camera.

Source of Information: The Chittagong Univ. J. B. Sci.,Vol. 4(1 &2):13-23, 2009

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

In the present observation mucous exudation was the general pathological symptom noted in the gills of Cd, Cr and Hg treated fishes. The mucous secretion along with proliferated primary lamellar epidermis could have form a respiratory exchange obstruction on its own. Damage of the pillar cell system, congestion of blood and necrosis in the lamellar epithelium were common in the cases of all three heavy metals. It may be inferred that this kind of lesion might affect the gill by reducing the supply of blood and might cause respiratory impairment.

Knowledge Management: Journal