Evolutionary adaptation of membranes to temperature.

TLDR

The fluidity of brain synaptosomal membranes from arctic and hot‑springs fish species, two temperature‑acclimated goldfish, and two mammals was measured by fluorescence polarization. Fluidity decreased from arctic sculpin to rat, correlating with increasing adaptation temperatures and indicating that both evolutionary adaptation and seasonal acclimation partially compensate membrane fluidity; higher temperatures increased saturated fatty acids and lowered the unsaturation index, with a significant correlation between these indices and membrane dynamics, underscoring homeoviscous compensation as a key component of temperature adaptation.

Abstract

The "fluidity" of brain synaptosomal membrane preparations of arctic and hot-springs fish species, two temperature water fish species acclimated to different seasonal temperatures, and two mammals was estimated using the fluorescence polarization technique. At all measurement temperatures, the fluidity decreased in the order: arctic sculpin, 5 degrees-acclimated goldfish, 25 degrees-acclimated goldfish, desert pupfish, and rat. This correlated with increasing adaptation or body (i.e., cellular) temperatures of 0 degrees, 5 degrees, 25 degrees, 34 degrees, and 37 degrees and suggested a partial compensation of membrane fluidity for environmental temperature that occurs over the evolutionary time period as well as during laboratory (seasonal) acclimation. Evolutionary adaptation of relatively stenothermal species to constant thermal environments resulted in a more complete compensation than laboratory (seasonal) acclimation. Each compensation is accompanied by differences in the saturation of membrane phosphoglycerides. At increased cellular temperatures the proportion of saturated fatty acids increased and the unsaturation index decreased; the correlation between these indices and the measured expression of membrane dynamic structure was highly significant. It is concluded that the homeoviscous compensation of synaptic membrane function is an important component of temperature adaptation.