Membrane order and ATPase activity as correlates of thermal resistance acclimation of ciliary activity in the gills of Anodonta

Abstract

1.1.|The activity of frontal gill cilia is more heat resistant in warm-acclimated (24°C) than cold-acclimated (4–6°C) fresh water mussels (Anodonta cygnea cellensis).2.2.|The order of microsomal membranes prepared from the gills of warm-acclimated animals is between 3 and 45°C higher than that of membranes from cold-acclimated animals.3.3.|n-Hexanol decreases the heat resistance of ciliary activity and decreases membrane order; these variables are equally sensitive to its effect.4.4.|Mg2+ and Ca2+ increase the heat resistance of ciliary activity and increase membrane order at high temperatures.5.5.|Thermal acclimation has no effect on the activity, its temperature dependence, or on the Km of microsomal membrane-bound (Mg2+ or Ca2+) ATPase of gills.6.6.|Thermal resistance acclimation of ciliary activity is probably a side-effect of the partial homeoviscous adaptation of gill cell membranes.