Tokyo, Japan -- A fish with transparent blood and a big heart is a prize catch for a Japanese aquarium.
Tokyo Sea Life Park is boasting the world's only ocellated ice fish in captivity. The fish was caught in the freezing waters of the Antarctic Ocean.
Scientists say the ice fish has no hemoglobin, a protein found in all other vertebrates that gives blood its red color and is what carries through the body.
Satoshi Tada, an education specialist at the Japanese aquarium, says it is still a mystery how the fish can survive without hemoglobin.
"It may be somehow related to the fish's large heart," Tada says, and that it may be blood plasma that circulates oxygen throughout its body.