FREEZING SURVIVAL AND METABOLISM OF BOX TURTLES, TERRAPENE-CAROLINA

Adult eastern box turtles Terrapene carolina carolina from Ohio readil y recovered after 44 h of freezing exposure at -2 C. During thawing at 25 C, motor responses resumed in a sequence of increasing complexity with a reflex twitch in response to poking seen after 1.2 +/- 0.5 h, c oordinated retraction of the limbs after 2.0 +/- 0.18 h, and voluntary locomotion after 2.7 +/- 0.4 h. Turtles dissected immediately after f reezing exposure had ice in body cavities and surrounding skeletal mus cles in limbs. Analysis of putative cryoprotectants in serum and seven organs showed that all organs accumulated glucose during freezing. Ne t glucose accumulations of 6-20 mumol/g wet weight represented 4-22-fo ld increases; the highest glucose levels were in liver, heart, and ser um. Liver glycogenolysis was identified as the source of the glucose; this was supported by both metabolite (a 62.5-fold increase in the pre cursor glucose-6-phosphate) and enzyme (the percentage of glycogen pho sphorylase in the active a form rose from 21.3-57.5%) responses to fre ezing. Freezing exposure also caused an increase in lactate levels in serum and four organs, but glycerol (<2 mumol/g), sorbitol (<0.3 mumol /g), and free amino acid levels in organs were unchanged. Both the low levels of putative cryoprotectants and measurements of serum osmolali ty, 244 +/- 4.3 and 315 +/- 15.4 mOsmol/l for control and freezing exp osed turtles, indicated that box turtles can endure freezing without a n accumulation of large pools of low molecular weight cryoprotectant.