Turtle (Chrysemys picta bellii) Shell Mineral Content Is Altered by Exposure to Prolonged Anoxia

Freshwater turtles (Chrysemys picta bellii) are well known for their remarkable ability to tolerate prolonged anoxia. One of the responses to this stress is a large increase in plasma divalent ions. Our measurements of shell mineral composition before and after long-term anoxic submergence support the assumption that calcium and magnesium are mobilized from skeletal sources. While the loss of calcium from the shell is not likely to substantially affect the calcium content of the whole animal, a significant portion of the whole-animal magnesium may be lost during normal overwintering. We also evaluated the renal response to anoxia and found a dramatic decrease in glomerular filtration rate, which may enhance the rise in body luid divalent cations.