Lantern Shark Light Switch Powered By Hormones
Lurking in the dark, murky depths of the world’s oceans are quite the number of fascinating creatures. Very little sunlight reaches these deep places of the world, but should you ever decide to brave these territories, you may find yourself amidst a spectacular light show—all courtesy of nature.
Bioluminescence is a common thing for many creatures, especially those who lurk between the devil and deep, blue sea. Some glow-in-the-dark creatures you may already be familiar with are things like fireflies, glowworms, anglerfish and some forms of squid. Plants also have developed such characteristics, including 7 fungi that joined the ranks earlier this year.
Photo by Etrusko25 (Image source: Wikimedia Commons)
Now, it was believed for the longest time that these bioluminescent species all powered their lighting effects in the same way: through nerve cells. However, scientists have recently discovered one animal—possibly more, pending on further research—that does not rely on nerves. Instead, their on/off switch is powered by hormones; and the odd species out would be the Velvet Belly Lantern Shark.
The first discovery of its kind, Belgian researchers found that melatonin, prolactin and alpha-MSH are responsible for the glowing quality of these sharks. Making such a find supports theories that glowing capabilities have evolved numerous times in animals. Julien Claes, co-author of the study, suspects that other sharks may also rely on hormones rather than nerves to create the glowing effect, as well. Not all sharks have the ability to light up, mind you, but at least 1 out of 8 do, and Claes intends to study them further. “It’s amazing—this work just shows that bioluminescence is a very complex phenomenon,” he says. “We are still really at the beginning of this story.”
Since the lantern shark uses 3 different hormones to produce the on/off lighting effect, each hormone serves a different purpose. First, we have melatonin: known as the “dark hormone”, it is useful for sleep regulation in humans, and apparently it provides a slow, long-lasting glow in sharks—capable of lasting for several hours. Scientists speculate this glowing method allows the sharks to camouflage themselves, counter-illuminating them from below as they descend further down into the sea. Melatonin is also used by other animals, particularly during those long, winter nights; as it is released by the pineal gland, where information on the amount of external light is stored.
Next on the list, we have prolactin. This produces a glow at a much faster rate, but it only lasts about an hour. Still unsure of the reasons for this, researchers suspect it may have to do with signaling other sharks or potential mates.
Last of all, the off-switch of the shark comes in the form of alpha-MSH. This hormone can be contributed to the darkening of skin in a number of species (including humans), though when released into the brain it can also have effects on appetite and sexual arousal.
The bioluminescent ability has happened numerous times throughout the evolution of animals and the world. It makes me wonder how long it will be before people start using similar traits or techniques. Who knows, perhaps a thousand years from now, courtships will be rated on who gives the best light show, rather than expensive dates.
The full report of the study will be published in the Journal of Experimental Biology on November 15th.
By Heidi Marshall
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Tags: bioluminescence, bioluminescent animals, evolution, glow-in-the-dark species, hormones, new discovery, velvet belly lantern sharks
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