A study of some factors involved in the adaptation to temperature in the freshwater crayfish austropotamobius pallipes (lereboullet)

Abstract

The phenomena of resistance compensation to temperature and heat death in the freshwater crayfish Austropotamobius pallipes has been studied, with particular regard to muscle membranes. The lipid composition of whole muscle was analysed by conventional chromatographic techniques. The principle phospholipids present were choline phosphoglycerides (50%), ethanolamine phosphoglycerides (25%) and serine/inositol phosphoglycerides (10%). Temperature acclimation had no effect on the phospholipid composition. The fatty acid composition of various phospholipid classes were also analysed by GLC and were found to be highly unsaturated. Total phospholipid extracts from animals acclimated to 4 C (18 hr light photoperiod) contained as lightly greater proportion of unsaturated fatty acids, compared to extracts from 25 C acclimated crayfish. The acidic phospholipids showed the greatest changes. Acclimation to 4 C with 8 hr light photoperiod conditions caused incorporation of a still greater proportion of unsaturated fatty acids into membrane phospholipids. This daylength effect, however, was not associated with a change in the thermal resistance of the whole animal. The overall activity of the Ca(^2+) stimulated ATPase of crayfish sarcoplasmic reticulum was unaffected by thermal acclimation, although warm-acclimated crayfish yielded significantly more microsomal protein per gram muscle weight. The kinetics characteristics of enzyme activity were independent of temperature up to 28 C. Incubation at 35 C (a lethal temperature) caused a decline in enzyme-substrate affinity. Thermal acclimation had no effect upon these characteristics. Arrhenius plots of enzyme activity for preparations isolated from both acclimated groups were linear. The activation energy for the enzyme from each acclimation group was similar (approximately 15 Kcals. Mole(^-1) ; 62,8 KJ. Mole(^-1)).The process of inactivation of the Ca(^2+)-stimulated ATPase at lethal temperature was also studied. High KC1 media protected the enzyme from inactivation, although dilution, and addition of BSA and calcium had no effect. Inactivation in low KC1 media, was a first order process. Acclimation had no significant effect upon the rate of inactivation. The proposed role of membranes in the phenomenon of resistance compensation has been discussed in the light of this and other data. An ultrastructural and histological study of a Microsporidian parasite of crayfish muscle is also presented.