Bioluminescent Sharks Set the Sea Aglow

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.

Researchers studied three species of bioluminescent sharks near the Chatham Islands, New Zealand
Coastline of one of the Chatham Islands, New Zealand
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Millions of Pickles, Pickles in the Sea

For a few years beginning late in 2013, warmer ocean conditions in the eastern Pacific prompted the appearance of unexpected species and toxic algal blooms that devastated others. When temperatures cooled in 2017, the marine ecosystems seemed to be returning to normal. Except for the pyrosomes. Although these previously rare organisms did start to wash up on beaches during the periods of warming, they began to appear by the millions from Oregon to Alaska that spring.

Photo by Steven Grace.

Some combination of ideal conditions led pyrosomes to multiply, dominate the ocean surface and wash up on beaches along the US and Canadian Pacific Coasts. Pyrosomes typically exist offshore, far below the surface in warm, tropical waters all over the world. Their sudden proliferation in other areas is likely due to the warm, Pacific ocean “blob,” although atypical sea currents and changes in pyrosome diet have been offered as other possible explanations.

While the appearance of pyrosomes impeded the efforts of fisherman by clogging nets and filling hooks, greater ecological effects have yet to be observed. As we celebrate World Oceans Month, pyrosomes offer a mesmerizing example of the astounding biological diversity our oceans have to offer and, perhaps, a cautionary tale of the impact climate change can have on those marine lifeforms.

The pyrosome species common in the NE Pacific, Pyrosoma atlanticum, goes by a few other colorful names. Each name reveals something captivating about these creatures. Commonly called “sea pickles” due their size, shape and bumpy texture (like a transparent cucumber), these are not single organisms, but colonies formed by hundreds or thousands of individual multicellular animals call zooids.

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Bioluminescence from the Sky to the Ocean Depths

It is nearly one month past the summer solstice and here in southern Wisconsin, the glow of fireflies at dusk and into darkness is a summertime pleasure not to be missed.

Fireflies employ the substrate luciferin and the enzyme luciferase, to produce their bioluminescence. The flash of a firefly lantern is designed to attract a mate, although with some species the potential mate becomes prey. Different species of fireflies have different flash patterns, which helps them find one of their own, when pairing off to create new little shiners.

A Photinus sp. firefly with glowing lantern. Image from art farmer, Indiana.
A Photinus sp. firefly with glowing lantern. Image from art farmer, Indiana.

In contrast to showy bioluminescence during night time flight, ocean depths have luminescence displays from a wide variety of creatures. Many of these bioluminescent sea creatures are recent discoveries, their discovery, habitat and behavior identified with the use of mini-submarines and non-manned submersibles.

One glowing example is the cluster wink snail. Terrestrial snails have been noted to leave a slightly luminescent trail of snail mucus as they crawl. But in 2010, the cluster wink snail was noted to flash a bright green light throughout  its entire shell. What better than an illuminated shell?

The snail has been noted to light up when disturbed, perhaps because the light makes the snail look larger. Or the bright flash may attract larger predators to come closer, scaring away the initial interrogator.

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