Shark researchers working off the eastern coast of New Zealand have made an illuminating discovery. In a new study, published in the journal Frontiers in Marine Science, the scientists found that three species of deep-sea shark are bioluminescent, producing a soft blue-green light with specialized cells in their skin.

One of the species, the kitefin shark, grows to a length of nearly six feet, making it the largest known bioluminescent vertebrate. Giant squid, which get much bigger, are also known to produce light.

Bioluminescence had previously been documented in only around a dozen shark species, so this discovery significantly adds to our knowledge of how prevalent the phenomenon is in