Accessory cells in teleost branchial epithelium

Abstract

Correlated morphological and cytochemical investigations of the branchial epithelium of the pinfish, Lagodon rhomboides, have revealed a cell type that is invariably associated with chloride cells. These cells, termed “accessory cells,” have been described previously in the teleost pseudobranch (Dunel and Laurent. J. Microsc. Biol. Cell 16:53-74, 1973) but not in the gill proper. Accessory cells are more numerous in pinfish adapted to seawater than to 33% seawater, and in the former participate with chloride cells in the formation of apical crypts. Although accessory cells are much smaller than chloride cells, they possess numerous mitochondria and display an abbreviated labyrinth of plasma membrane-derived tubules. The labyrinth membranes of accessory cells are essentially unreactive, however, when processed for Na-K-ATPase localization by K-nitrophenylphosphatase cytochemistry, whereas chloride cell membranes exhibit copious, ouabain-sensitive reaction products. The zonulae occludentes between accessory cells and chloride cells also appear to be less extensive than those between either of these cells and the flanking pavement cells. These features suggest that accessory cells represent a population of partially differentiated chloride cells.