Fish with Clear Blood Lives in Antarctica

[n2doc]

Researchers from Japan have now found how a fish with transparent blood lives in the frigid waters of Antarctica at a depth of 3,300 feet.

The fish, called Ocellated Ice Fish, is unique because it lacks an essential protein in its body that transports blood in all vertebrates. The protein- hemoglobin- also makes the blood appear red in color, reports AFP.

The Tokyo Sea Life Park is the only aquarium in the world that has the Ocellated Ice Fish.

"Luckily, we have a male and a female, and they spawned in January," said Satoshi Tada, an education specialist at the center, reports Discovery News.

more
http://www.natureworldnews.com/articles/1246/20130406/fish-clear-blood-lives-antarctica.htm

[mike_c]

1. rather important typo...

"The fish, called Ocellated Ice Fish, is unique because it lacks an essential protein in its body that transports blood OXYGEN in all vertebrates."

on edit: Without some sort of O₂ carrier, O₂ transport would presumably be restricted to diffusion distances and rates, which are typically much to small and slow to effectively carry dissolved respiratory gasses from the gills to the systemic tissues. If the fish is very small, maybe the combination of cold temperature and high pressure helps somehow, but that's just idle speculation. This would never be possible for an endothermic vertebrate under any conditions.

[GiveMeFreedom]

2. I am challenged by your explanation.

Is this some sort of missing link? Alien? Platypus? Thanks. Peace.

[mike_c]

3. well, it's certainly odd....

Sorry for the obtuse comments. Get ready for a physiology lesson.

Animals have various kinds of respiratory surfaces, such as the interior of the lungs in terrestrial vertebrates and the gill surfaces of fish. Gas exchange between the surrounding medium and the fish's blood takes place at the respiratory surface (which must be wet, in all animals, for gas exchange to take place). Respiratory gasses are transported to the systemic tissues throughout the body such as muscles, organs, and so on where O₂ is consumed by oxidative metabolism and waste CO₂ is produced. This waste must be transported back to the respiratory surface for removal from the body. Respiratory gasses are usually (but not always) transported to and from the respiratory surface and the systemic tissues by the circulatory system, i.e. in the blood.

Respiratory gasses like O₂ and CO₂ will dissolve in water, including the aqueous solution in blood plasma (the liquid portion of blood), but only in relatively low concentration. Further, exchange of respiratory gasses into solution at the respiratory surface and between the blood and the systemic tissues is usually aided by respiratory gas carrier molecules, such as hemoglobin. Hemoglobin not only carries respiratory gasses in the circulatory system, it also facilitates the exchange of gasses at the respiratory surface, where O₂ is loaded into the blood, and at the systemic tissues where O₂ is effectively exchanged for CO₂. So hemoglobin allows blood to carry much more respiratory gas than would be possible in solution alone, and it facilitates exchanging those gasses at the respiratory surface and in the capillaries of the systemic tissues.

Without hemoglobin (or some other carrier), respiratory gasses can only be carried in solution at very low gas concentrations, usually way too low to sustain oxidative metabolism in cells throughout the systemic tissues. Further, it's exchange rates when it moves between solution in the blood and the respiratory surface and the systemic cells is limited to physical diffusion, which is slow in water and only operates over very short distances during physiologically meaningful time scales.

That's why all other vertebrates have hemoglobin in their blood-- to provide a transport mechanism for respiratory gasses between the respiratory surface and the systemic tissues that can move much higher volumes of gas than can be moved in aqueous solution alone, and to provide biochemical gas exchange reactions that are much faster than simple physical diffusion.

Tiny invertebrates (diffusion only works over very short distances) and animals with very low O₂ needs can rely on dissolved gasses and diffusion within limits, but I'm not aware of any vertebrate except possibly this one that can get away with that.

Hope that helps!

[GaYellowDawg]

6. Good explanation

However:

Gases, including oxygen, dissolve at a much higher concentration at lower temperatures and higher pressures, allowing enough oxygen to dissolve into this fish's plasma to actually do the job via diffusion. How else could you explain the secondary loss of hemoglobin expression?

I've used this fish as an example of an evolutionary dead end to my classes for a couple of years. The fish's hemoglobin genes have degraded, and can't be recovered. Although this fish is very well adapted to a very specific environment, changes in that environment - and I use climate change at the poles as an example - will result in extinction.

The most amazing part of that article, to me, was the fact that this fish has been successfully been bred in captivity. I wonder how they're oxygenating the water to the necessary level without putting it under high pressure?

[phantom power]

4. I'm gonna predict it's got some kind of hemoglobin mutation

and a pretty damned interesting mutation that must be, if that's what it is.

[mike_c]

5. with clear blood?

That would require hemoglobin without the heme, which is the oxygen binding part. But I agree with you that having no oxygen carrier is tough to swallow unless the fish's oxygen needs are shockingly low for a vertebrate. That sounds dubious even for a tiny poikilotherm.

[GaYellowDawg]

7. Phantom's right.

It is a mutation in hemoglobin; in fact, there's been an evolutionary secondary loss in the hemoglobin gene. I got to see Sean Carroll talk about this fish at an NABT (Nat'l Assoc. Bio Tchrs) meeting a few years ago. Absolutely fascinating. The fish lives in an environment that is so low temperature and so high pressure that enough gas can dissolve into the fish's plasma to oxygenate via diffusion. For more information:

Cocca, E., Ratnayake-Lecamwasam, M., Parker, S.K., Camardella, L., Ciaramella, M., di Prisco, G., Detrich III, W.H., 1995. Genomic remnants of alpha-globin genes in the hemoglobinless Antarctic ice fishes. Proc. Natl. Acad. Sci. U. S. A. 92, 1817–1821.

Acierno, R., MacDonald, J.A., Agnisola, C., Tota, B., 1995. Blood volume in the hemoglobinless Antarctic teleost Chionodraco hamatus (Lönnberg). J. Exp. Zool. 272, 407-409

[phantom power]

8. I'd give myself partial credit

I was imagining a hemoglobin mutant without the iron, but that still retained (somehow) some oxygen transport functionality.

[GaYellowDawg]

9. Hm.

It's pretty much a transition-metal ion that's at the functional heart of all known oxygen-carrying proteins, whether you're talking about hemoglobin (Fe) or hemocyanin (Cu), so that would be difficult. But here are some cool pictures:

Icefish blood and blood containing hemoglobin:



Horseshoe crab blood containing hemocyanin: