The Antarctic Cod (Dissostichus mawsoni), also known as the Tootfish, is a species of fish of the family Nototheniidae. It produces antifreeze glycoprotein that allows it to live in the frigid waters off the coast of Antarctica. Its distribution range is generally below 65 degrees South. It is mainly caught in the Ross Sea in the austral summer but has also been recorded south of the Indian Ocean region, in the vicinity of the Antarctic peninsula, and near the South Sandwich Islands. Despite its name, it is unrelated to the true cod species. This fish is probably mesopelagic and is found as deep as 6500 feet.
Antarctic Cod have a lightweight cartilaginous skeleton, lack a swim bladder, and have fatty deposits which allow them to live in middle level waters. They also have retinas that are well adapted to the low light levels since snow and ice on the surface of the ocean, even in summer, reduces light levels to that of the great depths in the open oceans. Coloring is black to olive brown and lighter on the undersides. They have a broad head, narrow body, two fins running along the back and belly, large pectoral fins, and an additional small fin in front of the back fin. Antarctic Cod has been recorded up to 78.75 inches in length and weighing more than 300 pounds. Its flesh is white and high in oil content. It has a similar taste to cod, which led to its naming. They are the main fish predator in the Antarctic waters. Their primary predators are weddell seals, leopard seals, large squid, and Orca.
With a heartbeat once every six seconds, research involving Antarctic cod may lead to advances in cardiac medicine involving conditions where human hearts beat slowly during certain medical procedures or fail to beat fast enough due to hypothermia.