Structural changes in the gill cells of Gammarus duebeni (Crustacea, Amphipoda) under osmotic stress; with notes on microtubules in association with the septate junctions.

The amphipod crustacean Gammarus duebeni (Lilljeborg) tolerates salinities in the range freshwater to seawater. Such tolerance requires the ability to respond to the varying degrees of osmotic stress imposed on the single layer of epithelial cells separating the outside medium from the haemolymph space in the gills. Following transfer of individuals from low salinities to seawater, changes occur in the fine structure of the epithelial cells. These changes involve the configuration of the apical border of the cells, the mitochondria and cytoplasmic lacunae. Despite such variation in cell organisation, the association between neighbouring epithelial cells appears unaffected. Attention is drawn to a well developed system of microtubules in association with the septate junctions. The possible mechanical role of these microtubules in protecting the integrity of the septate junctions from the effects of osmotically induced changes in cell volume is discussed.