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

Abstract

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, Muller 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 reoxygenation (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 12hr 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.