ELNITSKY, Michael A.; LAYNE, JR., Jack R.; Slippery Rock University, PA: Effect of Tissue Freezing on Hemolymph Potassium Concentration in Gallfly Larvae.

Larvae of the goldenrod gallfly (Eurosta solidaginis) are tolerant of extensive tissue ice formation, facilitating their survival of the winter microclimate that prevails in their hibernacula (ball galls on goldenrod plants). These insects manifest a number of biochemical and energetic responses in support of their freeze tolerance. Nevertheless, tissue freezing may affect cellular homeostasis in Eurosta larvae as a result of changes in water distribution and in ATP production. We monitored hemolymph potassium concentration in recently thawed Eurosta larvae. The hemolymph potassium of unfrozen larvae was 35.5+1.2 mM. When larvae were frozen under a lethal condition (-80 C for 1 day), hemolymph potassium was significantly (t = 14.97, P < 0.0001) elevated to 59.4+1.0 mM. Freezing at -6 C, which is routinely survived byEurosta larvae, did not change (P > 0.05) hemolymph potassium even when the freeze went uninterrupted for three weeks. Hemolymph potassium was significantly (q = 8.38, P < 0.001) elevated in comparison to the control level (to 52.1+9.0) when the -6 C freeze went uninterrupted for 6 weeks. The changes in hemolymph potassium cannot be attributed to dehydration since body water contents remained stable during the freezes. Elevated hemolymph potassium under the -80 C freeze likely resulted from massive cellular disruption; whereas, redistribution of tissue water accompanying the -6 C freeze had no effect on the distribution of potassium. The rise in hemolymph potassium upon prolonged freezing at -6 C may relate to decreased activity of transmembrane pumps. This may be a regulated response helping to conserve ATP pools or it was a passive consequence of diminished ATP production.