Deadly fish known for their spikes and venom may pack a newfound weapon — switchblades on their faces, some of which can fluoresce green, a new study finds.

The discovery began when ichthyologist William Leo Smith at the University of Kansas at Lawrence dissected a wispy waspfish that had been his pet. Wispy waspfish are a species of stonefish, a group inhabiting Indian and Pacific coastal waters that are among the deadliest in the oceans. Many protect themselves with spikes or camouflage