The notoriety of “Shark Week” may be getting a flashy new upgrade, thanks to the phenomenon of glowing sharks. Certain shark species have been found to biofluoresce, illuminating the deep blue water in their vicinity with a light, bright green that is visible only to other sharks. The source of this light was previously unknown, but we now know that the hue is made possible by a family of small-molecule metabolites — a method of biofluorescence that differs from others that have been previously studied. And this finding could hold the key to benefits for the biomedical community. David Gruber with the ‘shark eye’ camera he built with his colleagues to simulate how fluorescent sharks appear to each other. Courtesy of David Gruber. David Gruber, a professor at The City University of New York, details his fresh catch of a discovery. “The exciting part of this study is the description of an entirely new form of marine biofluorescence from sharks — one that is based on brominated tryptophan-kynurenine small-molecule metabolites,” he said. Gruber and Jason Crawford, a professor from Yale University, focused on the skin colors of two particular species of sharks that biofluoresce — the swell shark and the chain catshark. After extracting chemicals from the light and dark skins of these two sharks, the researchers were able to detect a fluorescent molecule present in the lighter skins, yet absent from the darker ones. In addition to making the sharks look cool, these new biofluorescent molecules have displayed antimicrobial properties. Gruber explained, “These catsharks live on the ocean bottom, yet we don’t see any biofouling or growth, so this could help explain yet another amazing feature of shark skin.” He went on to speculate about the potential for these molecules to aid in central nervous system signaling, resilience to microbial infections, and photoprotection. Gruber and Crawford hope this new understanding can lead to a broader exploration of marine animal luminescence for the purpose of new imaging techniques, and they hope to study other luminescent marine animals. “If you can harness the abilities that marine animals have to make light, you can generate molecular systems for imaging in the lab or in medicine,” Crawford said. “Imaging is an incredibly important biomedical objective that these types of systems could help to propel into the future.” Don’t expect to find glow sharks on the shelves this holiday season, but the benefits from studying them could soon be felt by those out of the water. The research into this new brand of biofluorescence is promising. Perhaps one day other species will be able to biofluoresce in some way, under the watchful electronic eye of a biomedical professional. This research was published in iScience (www.cell.com/iscience/fulltext/S2589-0042(19)30244-5).