This question already has an answer here:

For example: humans have red, iron-based blood, and breathe oxygen, like most mammals. Would a creature with silver-based blood have black blood? What gas would they breathe and why? To summarize, how are the three things linked, if they are? Could you provide examples?


marked as duplicate by John, AlexP, Nosajimiki, Morris The Cat, JBH Jul 3 at 14:17

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.

  • 1
    $\begingroup$ the color doesn't depend on what you bearthe but what proteins you use to breathe i.e an animal that breathes oxygen can have green blood like worms and some squids or blue like crustacea, while some animals have transparent water like blood... $\endgroup$ – Charon Aug 7 '16 at 15:20
  • 1
    $\begingroup$ Ask on biology.stackexchange.com instead. $\endgroup$ – fredsbend Aug 7 '16 at 16:27

I believe I found the perfect National Geographic article for you.

  • Blood oxygen carrier - element - color - example animal
  • Hemoglobin - iron - red - humans
  • Hemocyanin - copper - blue - many octopodes
  • None - none - clear - ocellated icefish
  • Hemoglobin (which breaks down into biliverdin) - iron - green - green-blooded skink

Special: Hemargentum - silver - brownish black - I made it up

The purpose of these "carrier" materials is to make oxygen transportation more efficient. The ocellated icefish does not need a carrier material because it lives in water that is highly oxygenated already. Carrying this over to silver, the obvious transport compound would be silver oxide. Unfortunately, I believe silver oxide is chemically difficult to make, and this would result in a lot of wasted energy.

There's also the possibility of silver sulfate (Ag2SO4). Unfortunately, the standard way to create silver sulfate requires silver nitrate (AgNO3), and if you already have silver nitrate, I can't imagine turning it into silver sulfate is going to buy you more efficient energy transfer.

The problem I keep running into is that figuring out a plausible reason for something to have silver-based blood requires some deep organic chemistry knowledge. I hope I've given you a start, but you might need to find some biochemistry boards to ask on instead.


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