Fluorescent Mantis shrimp

Mantis shrimp are animals of all records! They have some of the best vision in the world, the fastest acceleration in the animal kingdom and they are also fluorescent! No need for a science fiction film with the squill!
But what is fluorescence?
Fluorescence is a light emission caused by the excitation of electrons of a molecule (or atom), generally by absorption of a photon immediately followed by spontaneous emission.