| Summary: | Australian and New Zealand Society for Comparative Physiology and Biochemistry. Auckland, N.Z., December 2012. Herbert, N.A.1, Skov, p.V.l, Tirsgaard, B.z and Steffensen, J.F. Z Only a few species of elasmobranch live in cold polar waters and the Greenland shark (Somniosus microcephalus) is the most notable example. These extremely large and long-lived sharks are thought to be sluggish but their active hunting lifestyle has recently been questioned by the finding of mobile prey species in their stomach (i.e. squid, fish and seal). The whole blood oxygen binding property of S. microcephalus was therefore examined on a recent research cruise to Greenland to provide clues on the aerobic potential of this species and to gauge the O2 carrying capacity of its blood during acute thermal change. The blood of S. microcephalus at 2oC revealed a high O2 binding affinity (P50 = 11.7 mmHg at a PCO2 level of 2.3 mmHg) and a surprisingly low sensitivity of binding to pH (the Bohr factor, ¿ = ¿log P50/¿pH = -0.22). Following an acute increase in temperature to 7oC, there was a slight loss of Hb-O2 affinity (P50 = 16.8 mmHg at a PCO2 level of 2.3 mmHg. P<0.05) but no significant increase in the Bohr factor (¿ = -0.35. P>0.05). The blood-oxygen transport system of S. microcephalus does not therefore appear compatible with an active lifestyle and is not overly sensitive to an acute rise in temperature. The implications of these observations will be discussed with respect to the known feeding ecology and depth distribution of the species.
|
|---|