Aquarium

This was not my first time to the Seattle aquarium, but I still saw a bunch of things I hadn't seen before like the birds, or the section with tropical fish. I feel it was a very good way to learn about marine life and the Pacific Northwest ecology, because you get to see marine life you would not normally see and get to talk to the experts about it. One of the most interesting things I saw was this fish.

I forgot the name of it, I like it because I think it looks really different. One thing I learned  was that the yellow eye rock fish can live over 100 years old, it really changed my perspective on it, because my dad has caught those fish before but I didn't know they could be so ancient.
Question: Why does the giant clam glow/ have bioluminescence?