PHOTO: Glowing Sea Animal Mystery Solved?

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May 26, 2009—Fluorescent proteins in some sea creatures may actually promote a healthy glow, according to a new study of a fishlike animal called a lancelet (pictured).

So-called green fluorescent proteins in the animals' bodies that do not cause brightness may instead act as antioxidants that protect the creatures in times of illness or stress.

Some fluorescent proteins do not cause animals to glow. So scientists wanted to find out why animals would have such proteins.

An early answer seems to be that the proteins suppress oxygen radicals—highly reactive molecules—from causing damage to the animal's body. The process may be similar to the supposed protective benefits of antioxidants in humans.

The new research is the first evidence that these non-glowing proteins plays a role beyond brightness.

"Despite a huge knowledge base about the biochemistry of [the proteins], little is known about their biological functions and our results clearly indicate that it is not always related to fluorescence," Dimitri Deheyn, a lead scientist at Scripps Institution of Oceanography, said in a statement.

Deheyn and colleagues ran an antioxidant bioassay, a commercially available kit that can determine a protein's capacity to prevent cell damage, on all the lancelet's fluorescent proteins. The team found that the proteins that make the animal glow have no antioxidant capacity, while the non-fluorescent proteins do.

Lancelets are the closest living invertebrate relatives of vertebrates, or animals with spines, and the thin creatures spend most of their time burrowed in coastal sands.

For the study, researchers collected a species of lancelet off Tampa, Florida.

Different proteins throughout a lancelet's body emit varying levels of fluorescence. For instance, the species has a more luminous head (head detail at top, and indicated with arrow in full-body picture at bottom).

(See more glowing animal pictures.)

The discovery will help scientists understand how the glowing proteins evolved across the animal kingdom, the scientists say.

Study published in the journal BioMed Central (BMC) Evolutionary Biology

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