Ultrastructure of the pseudobranch in the euryhaline Cyprinodontid fish, Rivulus marmoratus.

Abstract

AbstractThe ultrastructure of the pseudobranch of the euryhaline, self‐fertilizing fish, Rivulus marmoratus (Cyprinodontidae) was studied with thin sectio and freeze‐fracture transmission electron microscopy. In specimens raised from birth in 1% or 200% seawater, the pseudobranch contains two mitochondria‐rich cell types, pseudobranchial cells and chloride cells, each of which has an extensive tubular system. Chloride cells only occur on the lateral aspects of the pseudobranch, with their apical crypts open to the environment. Apical crypt invagination to a “pit” structure and multicellular complexes occur in both salinity extremes. The ultrastructure of chloride cells in 1% and 200% SW is consistent with that described previously in the opercular epithelium, opercular skin, and gill of this species; elaboration of mitochondria and basolateral membrane accompanies increased environmental salinity (King et al.: Cell and Tissue Research 257:367–377, 1989). Pseudobranchial cells constitute the majority of the cells; they do not extend to the surface but have a more organized tubular system that is continuous with the basal membrane. These cells do not exhibit ultrastructural changes in response to increased salinity. © 1993 Wiley‐Liss, Inc.