Question: Is it true that catsharks have bioluminescence?

Lesser-Spotted Catshark answered on 22 Nov 2017:

Close but not quite. Catsharks have biofluorescence which is a little bit different from bioluminescence. Catsharks will emit green visible light when hit with light of a different wavelength (blue to UV). UV (ultra-violet) light is high energy and penetrates the sea quite well so while many of the colours of what we call ‘visible’ light from red to violet get filtered out by the sea, UV penetrates quite well. When this hits the sharks they will absorb the UV and emit a green light. To be honest, we really don’t know very much about what its purpose is in catsharks! This has only very recently been discovered so well done for knowing about it. Some scientists have suggested it helps them to camouflage, or to find mates.

Some other sharks do exhibit true bioluminescence which means making their own light independent of absorbing another wavelength. These include some deepwater species like the lanternshark Etmopterus spinax. In this case they have specialized cells called photophores which will produce their own light using a trick of biochemistry!