The mackerel ice fish, also known as the crocodile ice fish due to its teeth and elongated head, is very unique among fish. It is also unique among the entire group of vertebrates. The mackerel ice fish is the only vertebrate that lacks hemoglobin. First recorded in 1954, the mackerel ice fish has nearly colorless blood due to this lack of hemoglobin. Hemoglobin is found in red blood cells and is what allows vertebrates to carry oxygen in their blood. Without hemoglobin, oxygen cannot attach. So how do these fish get oxygen to through their bodies?
Part of their name “ice fish” is given because these fish live in the frigid waters of
Ice fish have a denser concentration of veins and arteries supplying their high oxygen demand tissues. They also have large capillaries and blood volumes that are four times that of closely related red-blooded fish. Another feature of their body that assists with high oxygen delivery is the size of the heart. Ice fish have large hearts that beat almost twice as fast as their relatives and allow them to circulate a lot of blood very quickly. The ice fish also has a rather low metabolic rate and thus its need for oxygen is lower than that of other fish. It has also been speculated that they are capable of absorbing some oxygen directly through their skin.
I could not find any current research studies involving these fish, however I’m sure there are many interesting studies that could be done with them.
Posted By Erica Bonnell(1)