Shark Species Use Previously Unknown Molecules to Glow Green

A glowing chain catshark. (David Gruber / iScience)

(CN) – Two species of biofluorescent sharks discovered in 2016 use their fluorescent molecules for both communication and protection from bacteria, expanding what scientists know marine life is capable of, according to a study released Thursday.

Many deep sea creatures glow in the dark and alter the color of their skin for an array of reasons, but very few achieve this in the way swell sharks and chain catsharks do. They see the world from an entirely different perspective through a process known as biofluorescence.

The sharks take in blue ocean light and re-emit it to glow green in a way only visible to other sharks. Scientists have been baffled at how they accomplish this, but researchers have recently discovered this ability comes from a previously unknown family of molecules.

When they first discovered that swell sharks were biofluorescent, co-authors David Gruber and Jason Crawford wanted to know more about how this affects them and why it happens.

In their study published Thursday in the journal iScience, Gruber and Crawford studied these two shark species closely by extracting chemical samples from their skin and using fluorescent imaging to capture their elusive green tones. They found that specifically the light-skinned sharks had a rare fluorescent molecule responsible for the coloration.

These molecules give the sharks the unique ability to identify each other from the green glow, a fascinating feat considering most sharks are virtually color blind, but there is another possible purpose.

Similar small-molecule metabolites have been known to operate within the central nervous system and the immune system of other vertebrates. The scientists wondered if these newfound fluorescent molecules operate the same way and protect the sharks from microbial infections.

This was further suspected due to the fact that chain catsharks live near the ocean bottom where sediments contain an abundance of bacteria, yet show no signs of affliction.

When tested in the lab, the molecules taken from the skin of the sharks showed a notable resistance to the bacteria found in ocean sediments, proving that these molecules could have antibacterial properties.

This is a significant breakthrough for marine biologists working to understand these prehistoric creatures. Gruber and Crawford said they hope that with this new knowledge, they can investigate the concept of biofluorescence in other marine animals and utilize it in the medical field.

See video of the chain catshark here.

A glowing swell shark. (David Gruber / iScience)
%d bloggers like this: