This shark uses 'lightsabers' to thwart predators

You could say the Force is strong with with this shark.

 

The velvet belly lanternshark (Etmopterus spinax) uses built-in lightsabers —actually two bioluminescent spines on its back, making it a dual-wielding Jedi among its kind— to warn predators, the National Geographic reported.

 

But the lightsabers also help the lanternshark hide or make itself visible, according to a new study led by Julien Claes, a biologist from Belgium's Catholic University of Louvain.

 

For now, National Geographic said it is still unknown how the sharks create and control the lights on their backs.

 

Using counter-illumination, the lanternsharks light up their undersides to disguise their silhouette when seen from below, with the brighter bellies blending in with the light.

 

The sharks were found to have two rows of light-emitting cells - or photophores - on either side of a spine on the front edges of their two dorsal fins.

 

"Sometimes they flip around and try to hit you with their spines. So we thought maybe they are showing their weapon in the dark depths," said study co-author Jérôme Mallefet, who is also from Belgium's Catholic University of Louvain.

 

Translucent spines: more luminescent

 

The researchers found the lanternshark spines were more translucent than other shark spines. This let the spines transmit some 10 percent of light from the photophores.

 

They also found the glowing spines were visible from several meters away to predators such as harbor seals, harbor porpoises and blackmouth catsharks.

 

Mallefet said the bioluminescence "has all the characteristics to play the right role as a warning sign."

 

"It's a magnificent way to say 'hello, here I am, but beware I have spines,'" he added.

 

Yet, the study also found such warning signals are no obstacle to the lanternsharks' hunt for food.

 

Attracting mates: lightsabers are sexy

 

But aside from warding off predators, Claes also said the lanternsharks could also use bioluminiscence to attract mates.

 

"I also discovered during my PhD thesis that velvet belly lanternsharks have glowing organs on their sexual parts," he told National Geographic by email.

 

This "makes it very easy, even for a human, to distinguish male and female of this species in the dark!" he added.

 

Other species

 

The National Geographic report said many other species use bioluminescence as a warning signal, such as marine snails, glowworms, and millipedes.

 

Edith Widder, a marine biologist from the Ocean Research and Conservation Association, had discovered a jellyfish whose bioluminescence rubs off on attackers.

 

"It's like paint packages in money bags at banks," she said.

 

Widder also said glowing deep-sea animals use bioluminescence for various functions. — TJD, GMA News