Sharks Warn Off Predators by Wielding Light Sabers
Lanternshark uses light to camouflage itself and warn off predators, study finds.
by Helen Scales
Diminutive deep-sea sharks illuminate spines on their backs like light sabers to warn potential predators that they could get a sharp mouthful, a new study suggests.
Paradoxically, the sharks seem to produce light both to hide and to be conspicuous—a first in the world of glowing sharks.
“Three years ago we showed that velvet belly lanternsharks (Etmopterus spinax) are using counter-illumination,” said lead study author Julien Claes, a biologist from Belgium’s Catholic University of Louvain, by email.
In counter-illumination, the lanternsharks, like many deep-sea animals, light up their undersides in order to disguise their silhouette when seen from below. Brighter bellies blend in with the light filtering down from the surface.
Fishing the 2-ft-long (60-cm-long) lanternsharks up from Norwegian fjords and placing them in darkened aquarium tanks, the researchers noticed that not only do the sharks’ bellies glow, but they also had glowing regions on their backs…
(read more: National Geo) (photos: Jérôme Mallefet)