Determination of water “bound” by soluble subcellular components during low-temperature acclimation in the gall fly larva, Eurosta solidagensis

Abstract

1. 1. The water of hydration, or bound water, associated with soluble subcellular components was estimated using a microbalance drying technique and correlated with acclimation temperature in the overwintering, freezing-tolerant larva of the goldenrod gall fly, Eurosta solidagensis. 2. 2. Total water bound by soluble components of E. solidagensis increased as the temperature of acclimation decreased from 0.193 g/g dry wt in larvae acclimated to 22 °C to a maximum of 0.633 g/g dry wt in larvae acclimated to −30 °C. 3. 3. Using dialysis (membrane molecular weight cutoff = 12,000 daltons), low-molecular-weight, “dialyzable” components were separated from high-molecular-weight “nondialyzable” soluble components. Both fractions were found to contribute to the increase in water bound with decreased acclimation temperature. The increase was 2.5-fold for the nondialyzable fraction and four fold for the dialyzable fraction between 22 and −30 °C. 4. 4. Total water bound increased as a function of time at a constant acclimation temperature, and this increase was found to be due solely to an increase in water bound by the nondialyzable fraction. 5. 5. The molecular basis of water binding by both the dialyzable and nondialyzable fractions of E. solidagensis is discussed and the role of bound water as a mechanism of overwintering freezing-tolerance is evaluated.