Tokyo aquarium exhibits Antarctic icefish with see-through blood

by Hisashi Sasaki

Kyodo

The Antarctic Ocean-dwelling ocellated icefish is an anomaly in the natural world, as the only vertebrate with transparent blood.

Icefish have “no hemoglobin that carries oxygen into the blood,” said Naoaki Kawahara, a fish keeper at Tokyo Sea Life Park, the only aquarium in the world to exhibit the unusual creature.

Hemoglobin is the protein that normally gives blood its red color, but its absence in the icefish also means the species has white muscles, liver and even gills, which are normally bright red.

While an icefish has a big heart that sends a large amount of oxygen-carrying blood plasma throughout its body, the fish is known to take in oxygen through not only its gills but also the surface of its body.

The abundance of oxygen in the cold Antarctic Ocean is believed to contribute to the survival of the fish. But it is still unknown why the blood of the fish contains no hemoglobin.

The plan to exhibit icefish started after the aquarium learned that Nippon Suisan Kaisha Ltd.’s krill boats occasionally catch the fish alive in the Antarctic Ocean.

“We asked Nippon Suisan for cooperation in bringing such fish to Japan,” recalled Kawahara, 39.

Kawahara and two other aquarium officials were sent 13 fish from five species from a Nippon Suisan fishing vessel in Punta Arenas near the southern tip of Chile in August 2011. The 70-hour transportation of the fish to Japan involved stops in Santiago and Toronto.

The water temperature in the container needed to be kept below 3 degrees so the fish could survive, but had dropped to minus 1.9 degrees. Nine of the fish turned up dead when the container was opened in Santiago to change its water.

Nevertheless, the four surviving fish, including two ocellated icefish, were safely brought to Japan.

Hearing the news at Dallas/Fort Worth International Airport in Texas, the three “felt relieved but remained shocked” by the death of the nine fish, said Kawahara, who was born in Kamakura, Kanagawa Prefecture, and studied marine science at a university in Florida.

“Above and below water is a totally different world,” said Kawahara. “You can see things in the sea that you can’t see on land.”

After a professor at the U.S. university told him scientists mostly dealt with deceased creatures, Kawahara decided he “wanted to handle living organisms and thought of working at an aquarium.”

After graduating from the university, Kawahara worked at aquariums in Hawaii and Atlanta before landing his current job in 2011.

“I belong to a section primarily for collection of living organisms,” Kawahara said.

While people tend to see an aquarium merely as a place to keep fish in tanks, “I want to tell them how and where various fish live and how we have collected them,” he added. “But it’s extremely difficult to do so.

“I want children to see many kinds of living organisms and feel something” about them, Kawahara added. “From time to time, we can learn from kids, who perceive things in ways adults cannot imagine.”