 The blood affinity for oxygen is also elevated.Normally, blood affinity for oxygen would change with changes in temperature experienced at gills (in comparison to warmer adjacent tissues); however, Hb in southern bluefin tuna shows insensitivity to temperature, and a reverse temperature effect between (Hb-O2 binding is endothermic).Due to their anatomical positioning, the heart and the liver are the coldest organs and significant work needs to be expended for them to serve a regionally warmer body.