The unusual use of glowing “lightsaber” spines help certain sharks protect themselves against potential predators, according to a new study published February 21 in the journal Scientific Reports.
The velvet belly lanternshark is a small species that lives deep within the waters of the Atlantic Ocean and Mediterranean Sea. The sharks are equipped with transparent spines along their dorsal fins which are illuminated by light-producing cells.
According to BBC News, researchers believe this feature is used to ward off predators swimming above by showcasing an area of the shark’s body that would be difficult to swallow. If this proves to be the function of their “lightsaber” spines, the velvet belly lanternshark will be the first known species of fish to employ bioluminescence as a defense mechanism.
The sharks also sport additional glowing cells along the bottom of their bodies. This is most likely a camouflage technique that helps hide the shark from predators below.
Lead study author Dr Julien Claes, a shark biologist from the Catholic University of Louvain in Belgium, explained:
“Imagine you are below the shark, the shark is swimming and you have the light from the Sun coming down. If you are just below the shark what you are going to see is a shadow. So imagine if the shark can actually produce a light, which is identical to the light produced by the Sun. Then the shadow of the shark is going to disappear.”
The dual mechanism is an unusual combination of strategies, according to Nicolas Straube, a researcher at the College of Charleston. While not affiliated with the new study, he spoke about the shark findings to Live Science:
“It seems [contradictory] on the first glance, but the counter-illumination is used to be invisible from potential predators attacking from below, while the spines could only be seen by predators attacking sideways or from above and it seems to be evolutionarily advantageous, to warn potential attackers beforehand: If you try to eat me, you will be pierced by these two nice spines. So, the two strategies may in fact work well in concert.”
What do you think about the “lightsaber” shark’s use of glowing spines to scare away predators?