I've been working on an alien species, and I wanted it to have a blood colour other than red. I was going to go with Coboglobin until I found the sites I was looking at providing diametrically opposite info.

The first one I looked at claimed that Coboglobin was best in warm, oxygen-rich environments, and was amber-coloured in the arteries and clear in the veins, and the second site I looked at claimed that it was best in cold, oxygen-poor environments and was clear in the arteries and amber in the veins. Obviously someone got it completely backwards, but I'm not sure which!

For reference, the species is roughly human-sized and has an upright build and is a very distant descendant of a type of animal that had characteristics of both insects and other arthropods - namely the circulatory system and closed respiratory system of land crabs - but has diverted massively since, to the point that it no longer fits that classification (mostly so I can get away with it being human-sized without having to deal with factors that limit insect and arthropod size, like the weight of pure exoskeletons and the poor oxygen-carrying capacity of Haemocyanin).

I've gotten some very helpful feedback, and now all I'd like to clear up once and for all is whether Coboglobin is more suited to warm, oxygen-rich environments as this source states or cold, oxygen-poor environments as this source states.


Coboglobin is colourless when deoxygenated and amber yellow when oxygenated.

Veins typically carry our deoxygenated blood, so it would be clear in the veins and amber yellow in the arteries.

Coboglobin also has a low tolerance for cold and low oxygen, so it's best used in consistently warm (~15 degrees Celsius sounds about right) temperatures, and highly oxygenated environments. Unfortunately, the high oxygenated environments suitable for this blood base makes this a poor contender for an environment humans could live in.

If you're purely looking for a different color than red, I would suggest Vanabins. Vanabins has a range of colors, starting from deep blue-purple when deoxygenated, and as the oxygen level increases, the blood changes color from green to blue to yellow.

For an environment that suits humans and your species, I would suggest using Hemerythrin as a blood base - Hemerythrin preforms equally as well regardless of environmental conditions, and can be used well in cold or warm and low or abundant oxygen environments. Unfortunately, it only works at 1/4th of the efficiency as other transport cell types. It promotes cell growth and regeneration, allowing faster healing, as well as giving immunity to carbon monoxide poisoning and resistance to nitrogen stress on the blood stream. It's Colorless when deoxygenated and violet when oxygenated.

Combine that with Erythrocruorin for the plasma, and you might be able to fix the inefficiency issues. Erythrocruorin is based around a massive complex of iron molecules, allowing it to transport many dozens or possibly even hundreds of times the amount of oxygen as hemoglobin. It's red, like hemoglobin, but much more intense. With a balance of the Hemerythrin and Erythrocruorin, you could possibly produce an interesting magenta.

  • $\begingroup$ That lines up with my first source, but not with my second. Hmm. My priority is less on the colour and more the environment the blood base favours, as that'd have knock-on effects on the biology and psychology of the race in question - for example, a high oxygen quotient would mean more fire hazards, which the species would have to adapt to. I'm trying to have the creature-building influence the worldbuilding and vice-versa. $\endgroup$ – Pcm979 Feb 4 '17 at 2:45
  • 1
    $\begingroup$ @Pcm979 Well, you didn't provide what environment you want the species to be in, so I can't really tell you which to use now can I? If you provide the environment desired, I'll edit my answer to include what blood type is best there. $\endgroup$ – Aify Feb 4 '17 at 2:54
  • $\begingroup$ The only prerequisite I have for the environment is that humans should be able to breathe the atmosphere for at least a while without dying. Beyond that I'm planning to to use the blood base's preferred environment to shape the planet, and not the other way around. All that said, I had started building the world based on the 'high Oxygen content/high temperature' assumption before I found the conflicting info and I'd be irksome to have to throw that out and start from scratch, but if the conflicting source is correct, I'd like to know. $\endgroup$ – Pcm979 Feb 4 '17 at 3:29
  • 1
    $\begingroup$ @Pcm979 Updated answer. $\endgroup$ – Aify Feb 4 '17 at 7:31
  • 1
    $\begingroup$ @Pcm979 That's quite interesting. Toxic blood to deter predation. Wonder if could work on vampires? Sorry, just a random thought. However, vanabins does give coloured blood, and possibly toxic too. Ain't science wonderful! $\endgroup$ – a4android Feb 4 '17 at 12:08

From Wikipedia: 'Blood of this type would be amber yellow in colour when in the veins while uncoloured and clear in the arteries.' I am pretty sure this is right.

  • 2
    $\begingroup$ Why are you "pretty sure"? $\endgroup$ – T.J.L. Feb 4 '17 at 1:58
  • $\begingroup$ I checked other scources $\endgroup$ – KingraHoundoomJazz Feb 4 '17 at 2:26
  • 3
    $\begingroup$ Then reference them. $\endgroup$ – T.J.L. Feb 4 '17 at 2:27
  • 1
    $\begingroup$ "Coboglobin blood would be colorless with a faint pinkish tinge when loaded with oxygen, but in the veins would take on a dark yellow or deep amber color. " 10.4 - Alien blood $\endgroup$ – KingraHoundoomJazz Feb 4 '17 at 2:43
  • 1
    $\begingroup$ Oh, well. I can't find that anywhere, so good luck. $\endgroup$ – KingraHoundoomJazz Feb 4 '17 at 2:55

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.