California swell sharks secretly transform the dark blue ocean depths into an intense neon light show by using uniquely specialized skin molecules to absorb ambient ocean blue…

A closer look

While we build neon signs, sharks have been hosting underground raves for millions of years. Deep underwater, all warm colors fade away, leaving only high-energy blue light. The California swell shark evolved totally unique brominated tryptophan metabolites in its skin to weaponize this environment. These molecules absorb the ambient blue light and violently kick the energy back out as glowing fluorescent green. To any predator without a specialized visual filter, the shark becomes invisible, but to other swell sharks, they glow brilliantly to identify each other in the pitch black.