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I've been working really hard for a while now on a race of creatures called Nordic mountain Valkyrie Dragons. They are large: around 7'ft tall, and 9'ft from nose to tail tip, and I'm trying to come up with a kind of blood that they might have. I don't want to use red, iron-based blood, as it wont really fit with the backstory I've given them, but I also want to have the blood be based on a metal that would actually function.

They live in a cold and mountainous area, so whatever kind of blood it is, it needs to be efficient in keeping them warm to whatever reach it can. On top of this, it needs to be able to function with relatively low oxygen levels, as they tend to live at very high altitudes. I am NOT just looking for color.

I have searched everywhere and found nothing, so I would really appreciate some help.


marked as duplicate by bilbo_pingouin, Frostfyre, bukwyrm, elemtilas, MichaelK Dec 12 '18 at 21:10

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

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    $\begingroup$ Related, if not duplicate. $\endgroup$ – Cadence Dec 12 '18 at 16:34
  • $\begingroup$ Other blood colors doesn't ask for anything other than color, whereas I am asking for kinds of bloods that would work, as well as meet specific requirements. How is that a copy? I'm not trying to be rude, I'm actually curious. $\endgroup$ – ThatCamal Dec 12 '18 at 17:09
  • $\begingroup$ I don’t believe it’s a duplicate, but I will say the first answer on that question has a graph you will find very useful. $\endgroup$ – Joe Bloggs Dec 12 '18 at 17:17
  • $\begingroup$ I agree that I don't think they're technically a duplicate, though I feel that the accepted answer also answers this question. $\endgroup$ – goodguy5 Dec 12 '18 at 17:18
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    $\begingroup$ I think it's being flagged as duplicate because you're essentially asking the same question. You ask what metals will function the way iron does (oxygen transport); the earlier question also asks what metals will work as blood components (and gives a specific list). If there is something more specific you're after, I'd suggest editing your query to clarify that issue. $\endgroup$ – elemtilas Dec 12 '18 at 21:07

Icefish style: clear blood.

The icefish has no hemoglobin or other oxygen carrying pigment. Oxygen dissolves directly in the blood.


The ocellated icefish, for example, has clear blood. It's not very well understood how or why this is. The red color of most blood is given by hemoglobin, a protein that carries oxygen along through the bloodstream to the organs that need it.

The ocellated icefish ("ocellated" refers to the eye-like spots that make up the fish's coloration) does not have any hemoglobin. Its circulatory system gets along without it: oxygen, rather than being transported by the hemoglobin, is fully dissolved in the plasma (the main liquid element of blood). At those cold temperatures, oxygen dissolves into plasma more easily, and the muscles of the fish's circulatory system are able to absorb oxygen directly from the plasma.

That's all helped along by the fact that the ocellated icefish has an extremely strong circulatory system. It's got a much larger and stronger heart than most other fish, and pumps blood through its body at a rate five times greater than the average fish.

Clear blood dragons need it cold and they need to stay cold; the colder the better. The warmer it is, the less oxygen dissolves in plasma and the less they can deliver to muscles and organs. Maybe you can rig some way in which they can dump excess heat into their breath weapon, leaving their bodies colder?

Also, the icefish is kind of sluggish. Your dragons could accumulate an oxygen store in myoglobin - that does not circulate but is part of the muscles. Oxygen stored in myoglobin is how whales can pull off their deep dives. That oxygen storage would enable a one time burst of activity on the part of the dragon.

  • $\begingroup$ Thank you for all of the additional ideas, I'll definitely use some of those $\endgroup$ – ThatCamal Dec 12 '18 at 18:04
  • $\begingroup$ Related, perfluorocarbons carry oxygen directly, better than hemoglobin. $\endgroup$ – user71659 Dec 12 '18 at 19:38
  • $\begingroup$ @user71659 - apparently tricky to evolve, though. I can't think of any biological molecules that contain fluorine. $\endgroup$ – Willk Dec 12 '18 at 19:45
  • $\begingroup$ @Willk Along with bones and teeth, fluorine shows up in plants. $\endgroup$ – user71659 Dec 12 '18 at 21:00
  • $\begingroup$ @user71659 - cool! Thanks for link! $\endgroup$ – Willk Dec 12 '18 at 21:16


  1. It's rare and there isn't really any data to indicate that it wouldn't work.
  2. It oxidizes faster than iron, so it is ideal for lower oxygen levels.
  3. It's yellow when oxidized, and white or silvery when not oxidized.
  4. It is generally considered to be non-toxic

PS. The metal that carries the oxygen around in the blood doesn't constitute a large enough fraction of the blood to have an effect on how well the fluid transfers heat. At the end of the day, all blood is mostly water, which is good at carrying heat. As far as keeping them warm, it's more about insulation and good circulation than anything else.


Look to nature

Well, hemoglobin is iron based, but hemocyanin is copper based and is used by many animals.

The Ocellated Ice Fish does not use metal hemoglobin or hemocyanin It depends upon the oxygen that simply dissolves in the blood plasma.

I suppose Cobalt and Nickel are also likely metals that bridge the gap between Iron and Copper and perhaps could be reasonable substitutes. Heavier elements are less viable due to relative scarcity if nothing else.


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