Modifications of gill ultrastructure and ionic composition in the crab Goniopsis cruentata acclimated to various salinities

Abstract

1. 1. The ultrastructure of the epithelium and intracellular ion content of posterior gills were investigated in crabs acclimated to 150, 100 or 25% sea-water (SW). 2. 2. In 150 and 100% SW the epithelial cells, rich in mitochondria, showed a well-developed system of apical membrane infoldings and dense arrays of microtubules. 3. 3. In 25% SW the cells appeared swollen, with abundant vacuoles, and the apical foldings became distorted; microtubules were absent and numerous septate desmosomes were apparent. 4. 4. While gill intracellular Na +, Cl − and K + contents remained fairly constant in all the media tested, the intracellular concentrations varied inversely in relation to cell volume, which was three times larger in 25% SW than in 150% SW. 5. 5. The morphological alterations of the gills may precede the breakdown of their regulatory capabilities.