Every animal with bones has blood with hemoglobin, which binds with oxygen and makes the blood appear red.Must be an evolutionary adaptation to protect against vampires.
Every animal, that is, except one.
The ocellated icefish (Chionodraco rastrospinosus) has gin-clear blood. And it has no scales. And it lives nowhere but the inky depths down to 3,200 feet (1 kilometer) in the icy waters off Antarctica. Other than that, it's just an ordinary fish.
... It's possible, some scientists speculate, that the icefish's unusually large heart might help move oxygen through its body using blood plasma instead of hemoglobin.
Also, with no scales to get in the way, the icefish may absorb some oxygen directly through its skin: Cold, polar water is richer in oxygen than warmer waters.
But the mystery surrounding the icefish's lack of hemoglobin may take years to solve. "More studies are needed on the question," Tada said.