HEAT-SHOCK RESPONSE AND THERMAL-ACCLIMATION EFFECTS IN THE GILLS OF ANODONTA-CYGNEA - CILIARY ACTIVITY, STRESS PROTEINS AND MEMBRANE FLUIDITY

1. After the transference of fresh water mussels (Anodonta cygnea) fro m 4 to 20-24 degrees C, the heat resistance of ciliary activity in gil ls is increased significantly in 1 day and then further in 1-4 days to a new steady level. 2. If gills isolated from animals at 4 degrees C are transferred to 24 degrees C, the heat resistance of ciliary activi ty increases in 18-24 h to a level steady for 3 days. This level is eq ual to that found in gills of whole mussels after 1 day at 20-24 degre es C. 3. The response of isolated gills is not due to isolation, but p robably to heat shock. 4. The transfer of isolated gills to the higher temperature induces in 24 h the synthesis of 90 kDa stress protein, b ut does not affect the cell membrane fluidity. 5. The heat shock respo nse occurs also in isolated gills, but the thermal resistance acclimat ion of ciliary activity only occurs in the gills of whole mussels.