Gill damage to catfish, Saccobranchus fossilis following exposure to chromium

Abstract

Air-breathing catfish, Saccobranchus fossilis, were exposed to 5.6 mg L−1 of Cr for 7 d under static bioassay conditions. Gill tissue was examined through the scanning electron microscope (SEM) for surface morphological changes. In the control fish, the gill epithelium on primary and secondary lamellae contained distinctive surface features consisting of whorled patterns of microridges (microfolds) with intervening grooves. The microridges and grooves on the primary lamellae surface were regular in their architecture; whereas, the microridges of secondary lammellae were further apart and discontinuous. Small pores were observed on primary and secondary lamellar epithelium. SEM study of chromate exposed gill morphological data revealed that hyperplastic reaction start locally in the primary and the secondary lamellar epithelium. It appears that the hyperplastic results from direct chromate damage to the epithelial cells. Other gill damages were edema, fusion of secondary gill lamellae and degeneration of epithelial cells. Marked ultrastructural alterations in the pattern of microridges and intervening grooves, and swelling of primary and secondary epithelial cells were evident at 5.6 mg L−1 of Cr level.