The Ocellated Icefish's heart pumps a lot of blood through its body to make up for the lack of hemoglobin lost through evolution. The icefish has a heart considerably larger than its similarly-sized cousins, like the Notothenioids, making them use up more than twice as much energy as their red-blooded counterparts. Fish in warmer areas of the ocean use about 5% of their metabolic rate to keep their heart pumping, whereas the icefish devotes more than 4 times as much! Icefish also have many more blood vessels for each organ in their body compared to red-blooded fish. All of these unusual characeristics in an icefish are simply there to counteract the lack of hemoglobin in the icefishes' blood!
