There's a family of cold-water fish, the Crocodile Icefish, who completely lack hemoglobin. https://en.wikipedia.org/wiki/Channichthyidae …
Replying to @St_Rev
An awful lot of blah, blah, blah in the wiki trying to explain how this evolved, while admitting that it is failing to do so.
12:38 AM - 12 Mar 2018
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