Fiber-Optic Wonder

Joanna Aizenberg, a scientist and one of Earth's most complex multicellular animals, entered a San Francisco store and encountered the elegant remains of Euplectella speciosa—a deep-sea sponge and one of Earth's simplest multicellular animals. Scientist and sponge might one day revolutionize fiber-optic cables, the thread weaving together our wired world.

Fiber-optic cables are basically bundled strands of optical fibers—filaments of glass and reflective cladding that transmit coded light. These fibers are crafted under high heat using expensive equipment. Because the fibers are not very flexible, the cable is hard to install and repair, and is prone to minute cracks.

The sponge Aizenberg encountered—called Venus's flower basket and other names—transmits light through resilient, flexible glass fibers made at sea temperature. Aizenberg and her colleagues aim to find out how.

Venus's flower basket is a type of hexactinellid or glass sponge whose skeleton is composed of needlelike spicules of silica. The sponge uses proteins to collect and arrange silica particles into hairlike glass fibers two to three inches long. Traces of sodium are added, making the glass fiber better able to conduct light. Organic material and concentric shells of glass encase the fibers for protection. According to Aizenberg, “You could tie [the fibers] in tight knots and, unlike commercial fiber, they would still not crack.”

This sponge lives in tropical waters and anchors itself to the ocean floor. It likely gathers luminescent (light-emitting) organisms and turns itself into a “fiber-optic lamp” to attract the plankton that it eats. Seeking protection from predators, other creatures live inside this cuplike sponge with a lattice top. Often, a mating pair of shrimp will swim in and remain for the rest of their lives.

As scientists like Aizenberg realize, connectivity means more than communication among humans. There's a sea of information to be learned when we connect with the unwired world as well.

Vocabulary

cladding:
A metal coating bonded onto another metal under high pressure and temperature.

concentric:
Having a common center.

filament:
A fine wire or thread.

lattice:
An open framework made of strips that overlap in a crisscross pattern.

spicule:
A small, needlelike structure.

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Activity

  1. Why do you think plankton are attracted to the light transmitted by the Euplectella speciosa?
    [anno: Plankton are probably attracted to the light produced by the Euplectella speciosa because the plankton probably think the light is sunlight. Some kinds of plankton make food by photosynthesis.]
  2. What kind of a relationship do you think the sponge has with luminescent organisms? Why?
    [anno: The sponge probably has a symbiotic relationship with luminescent organisms. The luminescent organisms provide a source of light to the sponge, which it then uses to attract food, and the luminescent organisms probably receive protection from the sponge.]
  3. What is another reason that an organism living in the sea might have for producing its own light?
    [anno: Answers may vary but could include that animals might produce light to scare away predators.]