Hematological responses of the grey carpet shark ( Chiloscyllium punctatum ) and the epaulette shark ( Hemiscyllium ocellatum ) to anoxia and re‐oxygenation

We compared the hematological responses of wild and captive populations of two closely related sharks to a standardized anoxic challenge and during a 12 hr recovery period in normoxia: the epaulette shark ( Hemiscyllium ocellatum , Bonnaterre, 1788) and the grey carpet shark ( Chiloscyllium punctatum , Müller and Henle, 1838). Compared to normoxic controls, a significant increase in hematocrit (captive 22.3%; wild 35.9%) coupled with a decline in mean corpuscular hemoglobin concentration occurred in epaulette sharks indicating erythrocyte swelling in response to anoxia. However, the grey carpet shark had a significantly increased hematocrit (captive 27.2%; wild 29.3%), erythrocyte count (captive 37.6%; wild 46.3%) and hemoglobin concentration (captive 31.9%; wild 31.5%), suggesting a release of erythrocytes into the circulation and/or hemoconcentration in response to anoxia. Plasma glucose concentrations were maintained in both wild and captive epaulette sharks and in wild grey carpet sharks during anoxia but increased significantly after 2 hr of re‐oxygenation (epaulette: captive 55.8%; wild 50.1%; grey carpet shark: wild 70.3%) and remained elevated for 12 hr. Captive grey carpet sharks had an immediate increase in plasma glucose concentrations after anoxia (96.4%), which was sustained for 12 hr of re‐oxygenation. Lactate concentrations significantly increased in captive and wild animals of both species after anoxia, reaching a peak at 2 hr of re‐oxygenation. Both species showed significant, yet divergent, hematological changes in response to anoxia and re‐oxygenation, which may not only prolong their survival and assist in recovery but also reflect their respective ecophysiological adaptations to the extreme environments that they inhabit. J. Exp. Zool. 311A:422–438, 2009 . © 2009 Wiley‐Liss, Inc.