Fiber-optic Sponges

The millions of long, thin, sharp silica spicules in Rossella racovitzae sponges, three-foot high brown organisms that inhabit the Ross Sea in Antarctica, give the sponge structure and shape, as well as ward off predators. Biologist Riccardo Cattaneo-Vietti, of the University of Genoa in Italy, and his colleagues have found that the spicules also pipe light into the sponge, much like fiber-optic wires. The transmitted light appears to support symbiotic photosynthetic green algae that produce sugars for the sponge. Cattaneo-Vietti and his colleagues determined how well the four- inch-long structures transmit light by bending a spicule 90 degrees and shining a red laser into it. About 65 percent of the light was transmitted one and a half inches from the top of the spicule; at approximately two and a half inches from the top (past the bend), 10 percent of the laser light was still getting through. Silica spicules are an essential part of all sponges, and Cattaneo-Vietti suspects they may have a similar light-piping function in many of them.