Glow-in-the-dark sharks found gracing the waters of Hawaii
This year’s been a tumultuous one, with the rare glimmer of gratifying news reminding us there’s hope for the world yet. One such tidbit was the discovery of a new species of shark off the island of Hawaii in July – the Etmopterus lailae, a member of the lanternshark family.
The sharks in question emit an ethereal glow known as bioluminescence, though not as we’ve ever seen it before. Most glow-in-the-dark creatures achieve their radiance through the secretion of bioluminescent chemicals, or symbiotic bacteria. The Etmopterus lailae buck this trend, however, emitting their light from tiny glandular organs known as photophores.
Aside from lanternsharks, there is only one other shark family that wields the same bioluminescent capabilities, namely kitefin sharks (Dalatiidae), making the discovery a pretty special one. The luminous predators were discovered in the waters surrounding the Northwestern Hawaiian Islands in the Pacific Ocean.
What is bioluminescence?
Bioluminescence is the emission of light preceded by a biochemical reaction, a trait registered in more than 700 genera of animals. The bulk of bioluminescent animals live in the ocean (Wired reported an estimate in 2011 that 80 to 90 percent of deep sea life have such an ability), an image beautifully brought to life by everyone’s favourite scene in Life of Pi…
Bioluminescence differs from its light-emitting counterparts phosphorescence and bioluminescence insofar as it doesn’t need a prerequisite intake of sunlight (or other electromagnetic radiation) to generate its light.
Lanternsharks deviate slightly from the trend of light emission by photophores in fish in general, with the latter displaying a proclivity for light emission by the production of either symbiotic bacteria or their own chemical reactions.
Meanwhile, researchers found that velvet belly lanternsharks do similarly emit visible light through photophores. However, the biological makeup of those tiny organs – a cluster of photogenic cells known as photocytes – suggests they are also involved in a number of other functionalities, including camouflage, communication, and finding a suitable mate (glowing genitals allow specimens to identify members of the opposite sex).
There you have it: bioluminescence isn’t just a glow-in-the-dark marvel. Rather, it serves the acute evolutionary purposes of ameliorated self-preservation, intraspecies communication and procreation.