Physiologically induced changes in intramembranous particle frequency in the axons of an osmoconforming bivalve

Freeze-fractured axonal membrane surfaces from the connectives of Mytilus edulis show an increment in particle frequency of 52% (fixed tissues) or 68% (unfixed tissues) after long-term adaptation to low salinity. Particle size distribution was unaffected by osmotic adaptation, but was significantly different in fixed and unfixed material. The possibility that these structural changes reflect the known increase in sodium pump frequency in this osmoconforming tissue is considered.