Every animal with bones hemoglobin in its blood, which carries oxygen through its body and gives blood its red color. Every animal except one – the ocellated ice fish which has water-clear blood.

The ocean’s depth have revealed a series of odd life forms in recent years, from giant squid to translucent sea anemones, but scientists say the ocellated ice fish discovered in 2011 is among the most fascinating creatures the world over.  This unique fish lives in the ice-cold waters of Antarctica at depths of up to 3,300 feet (1 kilometer), and the only specimens in captivity can be found at Japan’s Tokyo Sea Life Park. Apart from the fact that it has transparent blood and no scales, the ocellated ice fish is not much different than most of the fish species living in Earth’s waters.  But its two special traits have researchers baffled. Because hemoglobin is responsible for carrying oxygen through the body of vertebrates, it’s not yet clear how this species can survive without the metalloprotein which binds with oxygen. Several theories have been formulated on the subject, with some scientists speculating that the unusually large heart of the ocellated ice fish might help move oxygen using plasma instead of hemoglobin, and others saying that it may be able to absorb oxygen through its scale-free skin from the oxygen-rich waters of Antarctica. But the truth is very little is known about this fascinating creature and there are yet no facts to back up the claims.

Scientists hope the pair of ocellated ice fish at Tokyo Sea Life Park may help them unravel the secret to its unusual transparent blood. “Luckily, we have a male and a female, and they spawned in January,” Satoshi Tada, an education specialist at the center, told AFP. More specimens will give them the chance to conduct necessary studies.

via Livescience