Saltwater Fish Trivia Post: Ocellated Icefish

Saltwater Fish Trivia Post: Ocellated Icefish

Icefish image from Wikipedia

Icefish image from Wikipedia

Have you ever heard a sports enthusiast say something like, “I bleed [insert mascot] [insert mascot color]!” as a testament to how much of an uber-fan they see themselves as? Around here, lots of people say, “I bleed Eagles green!” to show their support of the Philadelphia Eagles.

Well, if the Ocellated Icefish was a sports mascot…their fans would have to say they bleed…transparent fluid? Ew, weird eh?

Ok, as far as introductions to a story go that’s probably one of my worst. But, it is the start to a pretty cool story about a strange little saltwater fish. It turns out that the Ocellated icefish, Chionodraco rastrospinosus,  is the ONLY VERTEBRATE in the known universe with transparent blood. No joke. A breeding pair of the fish are currently housed at the Tokyo Sea Life Park–the only aquarium in the world to have received live specimens of this unique saltwater fish.

It turns out that the fish is somewhat commonly caught live in krill fishing operations–which is exactly how these specimens found their way to Tokyo Sea Life Park in the first place.

The Ocellated Icefish belongs to a family of fish named Channicthyidae, which all lack the protein hemoglobin, which carries oxygen through the blood of virtually every other vertebrate species. Dissolved oxygen is transported in the plasma of these fish. Even though the other members of the Channicthyidae family lack hemoglobin, the Ocellated Icefish is the only species with transparent blood.

It begs the question, for me at least, where in the world this fish comes from? If nearly every other family of vertebrates on the planet has hemoglobin in its blood…where did this family of fish come from? How did the evolve with such a unique genetic feature? I personally wonder if the fish is in such a remote and inhospitable environment that competition was light–or if the lack of hemoglobin bequeaths an advantage we don’t yet understand.

Without hemoglobin, the fish are at an oxygen disadvantage compared with similarly sized fish–seemingly to compensate (in an evolutionary sense), the fish have a supersized circulatory system, with larger hearts, blood vessels and even up to 4 times more blood.  The fish have a slow metabolism (and therefore don’t need a lot of oxygen)

What a curious little fish. If anyone has plane tickets to Tokyo they weren’t planning to use, please let me know.

Saltwater fish trivia

Image from Wikipedia

What you would need to start an Ocellated Icefish Species Tank:

  1. A friend with a krill-fishing boat who knows how to catch krill in Antarctica
  2. A water chiller that can keep the temperature close to -1.9 degrees Celsius
  3. A way to pressurize the tank to recreate ocean depths of ~1km
  4. A DIY iceberg

Disclaimer: These are not actual plans for an Ocellated Icefish Species Tank

Anyway, I hope you enjoyed learning about this quirky fish as I did. But while we are on the topic of strange saltwater fish -what is the strangest saltwater fish or coral you have ever come across or read about?

Written by: Al Ulrich

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