DOUGHERTY, B.E*; MCNAMER, A.N.; CROCKETT, E.L.: Inverse Compensation for Fluidity in Mitochondrial Membranes from Thermally Acclimated Earthworms
Exposure to low temperature typically results in changes at many levels of biological organization including adjustments in both chemical and physical properties of biological membranes. We compare membrane fluidities in enriched mitochondrial preparations from the body wall of the earthworm (Lumbricus terrestris) after four weeks of acclimation to 5 and 15oC. Membranes from 5oC-acclimated worms are more ordered than membranes from 15oC-acclimated animals with significantly greater polarization values at all but one temperature measured with the fluorescent probe DPH. At physiological temperatures polarization values are 0.22 and 0.15 for 5- and 15oC-acclimated worms, respectively. Although reports of inverse compensation of fluidity (greater membrane order in cold-bodied animals compared with warm counterparts) are relatively rare, inverse compensation in the earthworm is accompanied by changes in the metabolic status of the animal. Supported, in part, by the Honors Tutorial College at Ohio University.
