A fish with gin-clear blood has gone on display at the Tokyo Sea Life Park in Japan. The pair was caught by krill fishermen in the Antarctic, who had to keep them alive for months at temperatures near freezing to bring them back. They’re the only specimens of Ocellated Icefish, Chionodraco rastrospinosus, known to be displayed in captivity anywhere in the world.
So far, so impressive. But let’s dispel a myth or two right away. Despite a report — multiplied endlessly around the internet the way these things get multiplied — that it’s the only vertebrate (let alone fish) with gin-clear blood, that’s not exactly true.
There’s an entire family of such fish, called the crocodile icefish or white-blooded icefish. Far from being just one whackadoo weird species, the ocellated icefish is just part of a decent-sized group of at least 25 recognized species — and maybe more waiting to be found — that live in the icy waters of Antarctica. For whatever reason, their ice-colored blood fits right into the frigid scenery when they’re hunting the mighty krill or other small fish.
As, you might expect from a fish with ice running in its veins, they like it brisk. In fact, they seem to prefer a temperature that’s right around the freezing point of salt water — a cool -1.9o C. Brrrr.
They’ve lost almost all of the hemoglobin in their blood, which is what gives our blood its red color. As a result, they have what biologists have described as “reduced cardiac performance.” That means that they have to have much larger hearts to get their gin-clear blood a-pumping through their inefficient little veins.
Even if they’re not the one and only, the icefish in Japan are indeed special, since they have survived being transported by guys who normally catch and eat fish to make their way to the safety of a public aquarium. Check out this video.
I like that bit at the end where the aquarium expert says that ocellated icefish tastes like chicken. Kidding. But apparently the fish with the gin-clear blood tastes pretty good.
[icefish larvae photo Professor Dr. habil. Uwe Kils via Wikipedia Commons “Picture of the Day”]