Nature of blue color in corals and fish

[pszemol]

Is blue color in corals and fish caused by pigment of mechanical structures filtering light, like in butterfly wings or bird's feathers?

https://youtu.be/3g246c6Bv58?t=323

Pszemol

 

[MondoBongo]

from what i have read, only Mandarin Dragonets (synchiropus splendidus) produce a natural blue pigment. they're one of the few things that does, apparently.

 

[EMeyer]

blue colors in corals typically result from chromoproteins, which are slightly modified versions of the same fluorescent proteins that are responsible for all the colors we see under blue lights.

These chromoproteins operate by straight up reflection and absorption like other pigments, rather than the interesting structural properties described in your video.

I have no idea abut blue colors in fish, but it seems plausible that similar things could happen in their scales.

 

[MondoBongo]

this is all i've been able to find on it:

https://bioone.org/journals/Zoologi...s-of-Callionymid-Fish/10.2108/zsj.12.811.full

https://en.wikipedia.org/wiki/Synchiropus_splendidus

S. splendidus is one of only two vertebrate species known to have blue colouring because of cellular pigment, the other being the closely related psychedelic mandarin (S. picturatus). The name "cyanophore" was proposed for the blue chromatophores, or pigment-containing and light-reflecting cells. In all other known cases, the colour blue is structural, as it comes from thin-film interference from piles of flat, thin and reflecting purine crystals.