Blood viscosity and hematological changes during prolonged submergence in normoxic water of northern and southern musk turtles (Sternotherus odoratus)

Musk turtles (Sternotherus odoratus) can survive at least 150 days of submergence in normoxic water at 3°C, during which time there are large increases in packed cell volume (PCV). We investigated the effects of submergence in normoxic water at 3°C on the blood viscosity of musk turtles from northern (Massachusetts) and southern (Alabama) locales. Blood was collected from air‐breathing turtles and after 20, 50, 100, and 150 days of submergence in normoxic water at 3°C. Hematological responses to submergence were similar in the two groups, therefore the results were combined. Packed cell volume increased steadily above that of controls after 20, 50, 100, and 150 days of submergence. Hemoglobin concentration also progressively increased above that of controls after 20, 50, and 100 days of submergence but declined to near control values after 150 days. Blood viscosity increased with increasing PCV; however, blood viscosity of musk turtles appears less affected by PCV than is blood viscosity of mammalian species. As such, musk turtles appear to be able to maintain adequate blood flow to tissues while increasing the oxygen carrying capacity of the blood during prolonged submergence. However, after 150 days submergence, oxygen delivery should decrease due to a reduced oxygen carrying capacity of the blood and an increased resistance to blood flow, which may limit the length of time these turtles can remain viable during hibernation. J. Exp. Zool. 287:459–466, 2000. © 2000 Wiley‐Liss, Inc.