Effect of freezing on the transmembrane distribution of ions in freeze-tolerant larvae of the wood fly Xylophagus cinctus (Diptera, Xylophagidae)

The present study shows that freezing of freeze-tolerant larvae of the wood fly Xylophagus cinctus caused Na+, K+ and Mg++ to move to electrochemical equilibrium across the cell membranes. Na+ and Mg++ moved from the haemolymph into the cells, while K+ moved the opposite way. The original distribution of ions was restored after the larvae were thawed. The transmembrane fluxes of ions were of the same magnitude in the frozen and thawed larvae. The redistribution of ions in the frozen larvae did not give rise to any apparent change in the volume of cells and haemolymph upon thawing, i.e. the redistribution of solutes appeared to be osmotically neutral.