TURTLE (CHRYSEMYS-PICTA BELLII) SHELL MINERAL-CONTENT IS ALTERED BY EXPOSURE TO PROLONGED ANOXIA

Freshwater turtles (Chrysemys picta bellii) are well known for their r emarkable ability to tolerate prolonged anoxia. One of the responses t o this stress is a large increase in plasma divalent ions. Our measure ments of shell mineral composition before and after long-term anoxic s ubmergence support the assumption that calcium and magnesium are mobil ized from skeletal sources. While the loss of calcium from the shell i s not likely to substantially affect the calcium content of the whole animal, a significant portion of the whole-animal magnesium may be los t during normal overwintering. We also evaluated the renal response to anoxia and found a dramatic decrease in glomerular filtration rate, w hich may enhance the rise in body fluid divalent cations.