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Sea Pickles Glow All By Themselves — Here’s How

By LIDA TUNESI

There is something captivating about animals that create their own light. Fireflies do it, jellyfish do it, and even some sharks light up on occasion. Now, researchers from Baruch College are figuring out how sea pickles shine.

Other researchers have proposed that sea pickles’ glow comes from bacteria that live within them. But the new work presents evidence that sea pickles, or pyrosomes, produce the light themselves. The discovery is a surprising example of convergent evolution, the authors say.

Professors Jean Gaffney, Krista Dobi, and David Gruber of Baruch College and The Graduate Center, Ph.D. student Andrew Guarnaccia, and former postdoctoral fellow Nehaben Gujarati authored the study, published in Scientific Reports.

Pyrosomes are tube-shaped, gelatinous marine creatures that are actually made of hundreds to thousands of tiny individuals called zooids, living as a colony. The researchers captured pyrosomes off the coasts of Brazil and British Columbia, and sequenced their genetic material.

They found a gene that looked very similar to a gene from a creature called a sea pansy. The sea pansy gene codes for a type of enzyme called luciferase. These enzymes facilitate light-producing reactions between oxygen and molecules called luciferins. The researchers found that indeed, the new gene also coded for a luciferase, and when they mixed that enzyme with a luciferin, the reaction gave off light.

Sea pickles sit on a branch of the animal tree of life called Chordata. But animals in two other phyla—Cnidaria, which include jellyfish and sea anemones, and Echinodermata, which include starfish and sea urchins—also have very similar luciferases. The work supports the idea that an enzyme “ancestor” with a completely different function evolved into a light-producing enzyme at least three times across different animal groups.

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David Gruber (Presidential Professor, Biology, Environmental Science) | Profile 1 | Profile 2
Jean Gaffney (Assistant Professor, Biology) | Profile 1
Krista Dobi (Assistant Professor, Biology) | Profile 1