An Ocellated Icefish (Chionodraco rastrospinosus) is now on display at Tokyo Sea Life Park, an aquarium in Edogawa, Tokyo. The species lives in the Antarctic region, but is extremely rare, and has never been collected or exhibited at any aquarium in the world. It is the world''s first living icefish display at an aquarium!

Most of the Icefish species have been caught around the Antarctic Peninsula in the depth from 5 to 1000 meters. They have no scales at all except along lateral lines, and the head is very depressed.

They are unique in that their blood is translucent like clear water. Almost all the vertebrates have hemoglobins in the blood, and the hemoglobins usually contain red pigments, but icefish lack hemoglobins.

We don''t know why they don''t have hemoglobins, which are very important proteins transporting oxygen in the blood stream. All we know is that the icefish''s large heart sends a large amount of oxygen-containing blood throughout the body, and that they take in oxygen not only through the gills but also through the body surfaces. High oxygen concentrations in the Antarctic sea also seem to help icefish to live without hemoglobins.

We dissected one of the icefish specimens brought to the aquarium, and observed their muscles, liver, and gills look indeed all white (photo above).

These ocellated icefish had been caught by a Japanese fishing boat in the Antarctic sea. The boat brought them to Punta Arenas, Chile, and we transported them all the way to Japan.

One of the specimens has been on display in the ''Arctic and Antarctic Seas'' tank from August 24, 2011. The world''s first exhibit of a very unique fish with transparent blood.

August 25, 2011

Copyright 2011, Tokyo Zoological Park Society
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