Till recently I thought Iridophores gets color from carotenoids obtained from food, mostly xanthophyll from algae like spirulina. Someone recently enlightened me by stating
I couldn't find much info on if fish can synthesize guanine or not and if spirulina plays any role in it. Any research out there regarding this subject?Pearls are made from guanine crystals deposited within the fish iridophores. I believe they are technically a type of purine. Guanine is an amino acid. So technically as long as a fish has a good quality balanced protein with a decent guanine content, pearl development will then be determined by genetics and definition more so by the deposition of carotenoids or purines around the edge of the guanine crystals.