Channeling light in the deep sea

Peter Weiss

A genus of sea sponges grows its own light-conducting fibers that are remarkably similar to commercial-grade optical fibers—and in some ways better. A team of U.S. and Israeli researchers that recently studied several Euplectella species says the primitive creatures' fibers might serve as a model for improved telecommunications fiber optics.

In the Aug. 21 Nature, Joanna Aizenberg of Lucent Technologies' Bell Labs in Murray Hill, N.J., and her colleagues report that the sponges' fibers, called spicules, have glass cores infused with sodium ions that enhance the fibers' optical properties.

Made at high temperatures, commercial fibers can't exploit such impurities because those additives tend to clump as the glass cools. Moreover, these heated-then-cooled fibers develop undesirable internal stresses. On both counts, Aizenberg says, human-made fibers might benefit if manufacturers could assemble them bit by bit at low temperatures, as the sponges do.

Other sponges previously found to sprout light-conducting spicules (SN: 8/4/01, p. 77: Available to subscribers at http://www.sciencenews.org/articles/20010804/bob13.asp) inhabit shallower water than does Euplectella and may harvest sunlight with their fibers. At the inky depths of 500 to 1,000 meters, says Aizenberg, Euplectella's fibers are more likely to transmit photons from bioluminescent organisms to help the sponges find their meals.

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Letters:

What would sessile organisms do with information provided by the light from "their meals?" Just because spicules on a sea sponge transmit photons doesn't mean that that's their function.

David Contey
Boulder, CO

Each Euplectella sponge houses a pair of bioluminescent shrimp. The researchers speculate that the spicules transmit the shrimps' light into the sponge's surroundings. The glow attracts organisms that the shrimp eat. In turn, the sponge feeds on waste products of the shrimp.—P. Weiss

References:

Sundar, V.C. … and J. Aizenberg. 2003. Fibre-optical features of a glass sponge. Nature 424(Aug. 21):899–900. Abstract available at http://dx.doi.org/10.1038/424899a.

Further Readings:

Weiss, P. 2001. Soaking up rays. Science News 160(Aug. 4):77–79. Available to subscribers at http://www.sciencenews.org/articles/20010804/bob13.asp.

Sources:

Joanna Aizenberg
Bell Laboratories
Lucent Technologies
Murray Hill, NJ 07974

From Science News, Volume 164, No. 12, September 20, 2003, p. 190.