Gill morphology in the zebrafish, Brachydanio rerio (Hamilton- Buchanan)

A light and electron microscopic study of the gills of the zebrafish, Brachydanio rerio , were made to serve as a morphological basis for future investigations. It was found that for fixation of B. rerio gills, a mixture of 1·5% gluturaldehyde and 1·5% paraformaldehyde gives a mucus-free surface. Morphometric measurements of structural components of the gill secondary lamellae were made. Observations at SEM were correlated with those made at TEM. The different cell types in the branchial epithelium were characterized. Chloride cells were mainly located in the interlamellar regions and on the afferent side of the primary lamellae. Two morphologically different chloride cells were seen. The first type communicates with the external environment through a reservoir-like lumen, which is normally absent in freshwater fishes. The second type of chloride cell has more direct contact with the ambient water, resembling chloride cells from other freshwater fishes. Another cell type with features similar to those of the rodlet cell was frequently observed. This cell is interposed between other types of cells in the epithelium, and sometimes junctional complexes were present between the rodlet cell and surrounding cells.