Many deep sea creatures are bioluminescent. However, before documenting the luminescence of the kitefin shark, Dalatias licha, there has never been a nearly six-foot long luminous vertebrate creature. In a recent study, Mallefet and colleagues examined three species of sharks: Dalatias licha, Etmopterous lucifer, and Emopterus granulosus and documented their luminescence for the first time. These bioluminescent sharks are the largest bioluminescent creatures known.
The Bioluminescent Sharks
Shark bioluminescence was described in the early nineteenth century, and roughly 10% of shark species are capable of producing light by bioluminescence. The kitefin shark alongside two other bioluminescent shark species, the black belly lantern shark and the southern lantern shark, live in what is considered the ocean’s “twilight zone.” At a depth between 200 and 1000 meters below sea level, the twilight zone lies beyond solar light penetration.
Glowing Aids In Hiding
Beyond being extremely fascinating, several evolutionary advantages may have led to the development of bioluminescence in sharks.
Scientists have discovered that sharks often use their bioluminescence to camouflage themselves to fend off potential predators and sneak up on prey. The blue glow allows them to break up their silhouette and appear invisible while roaming the twilight zone. In fact, the kitefin shark when examined had remains of smaller sharks in its stomach despite being one of the slowest moving shark species in the world.
What Helps Us Sleep Makes Sharks Light Up
Led by Dr. Jérôme Mallefet, scientists found that the bioluminescence of these sharks is controlled hormonally. Melatonin activates and regulates their bioluminescence. However, the exact details of how the sharks turn their bioluminescent light off are not completely understood. The “lights off” switch is thought to be controlled through a separate hormonal pathway.
A second study from Mizuno and colleagues, provides evidence that sharks use coelenterazine as a substrate for the luciferin-luciferase reaction in their bioluminescence system, contributing more data to the understanding of the appearance and evolutionary history of bioluminescence in living organisms.
Making the Most of Deep Sea Research
It is amazing that the deep sea is the biggest ecosystem on Earth yet the majority of it remains a mystery. Scientists and researchers continue to research the deep sea and the creatures that live throughout its depths. However, the reality is, that deep sea research is being hindered by changes to the ocean caused by environmental stresses and climate change. With luck as more discoveries like glow-in-the-dark sharks are made, more people will prioritize preserving the ocean and its marvels.
References
Mallefet, J. , Stevens, D.W., and Duchatelet, L. (2021) Bioluminescence of the largest luminous vertebrate, the Kitefin Shark, Dalatias licha: First insights and comparative aspects. Frontiers in Marine Science [ last accessed March 23, 2021]
Mizuno, G. et al. (2021) Lantern shark Etmopterus use coelenterazine as substrate for their luciferin-luciferase bioluminescence system [ https://www.biorxiv.org/content/10.1101/2021.03.01.433353v1?rss=1; last accessed March 10, 2021]
Want to learn more about other bioluminescent organisms? Check out this blog.
To learn more about the last 30 years of bioluminescent innovations and the discoveries they’ve enabled, please visit our 30th anniversary celebration page.
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