Spicules Transport Light

an orange puffball sponge is seen underwater in the pacific ocean

Biological Strategy

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Image: Ken-ichi Ueda / Flickr / CC BY NC - Creative Commons Attribution + Noncommercial

Capture, Absorb, or Filter Energy

Energy is naturally available in many forms, including kinetic, potential, thermal, elastic, radiant, chemical, and more. All living systems require energy to carry out their many activities, and have developed strategies appropriate to one or more of those forms. For example, some plants maximize their surface area available for capturing radiant energy from the sun while others have strategies to focus scattered light onto photosynthesizing areas.

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Distribute Energy

Many forms of energy are naturally available, including kinetic, potential, thermal, elastic, radiant, chemical, and more. All living systems require energy to carry out their many activities. Energy isn’t a physical object that can be held, so it also can’t be pushed, pulled, or carried. However, it can be transmitted or transformed. For example, the golden-scale snail has a tri-layered shell that dissipates, or transfers, forces from a predator biting down on it, thereby minimizing damage to its soft body inside the shell.

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Sponges

Phylum Porifera (“pore-bearing”): Sponges

Sponges may seem simple, but there’s more to them than meets the eye. True, they don’t have nerves, muscles, or organs. But they do have unique, specialized cells that help them survive. Collar cells have long tails or flagella that line the inner sponge cavity and funnel water through the body. Sponges are filter feeders, taking in large amounts of water and trapping tiny particles to eat. They also have small spiky spicules made of silica or calcium carbonate that help them keep their structure. There are at least 5,000 known species of sponges living in aquatic systems, with 98% of them in the ocean.

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Silica spicules in sponges transport light into the inner parts of the sponge by structurally arranging individual spicules in bundles.

“Here we show for the first time, that, as hypothesized 13 year ago, sponge spicules in living specimens transmit light into deeper tissue regions. Our results demonstrate that in opposite to the actual opinion, photosynthetically active microorganisms can also live in deeper tissue regions, and not only directly beneath the surface, when a light transmission system (spicules) is present.” (Brümmer et al. 2008:61)

“The spicule bundles of Tethya aurantium are arranged of a large number of single spicules, which are much shorter (several hundred μm), than the whole bundle (several cm). That means the detected light inside the sponges is transferred through the spicule bundle and is at the same time transmitted from the outer spicules to the subsequent more central spicules. This at the same time explains the finding of phototrophic organisms along the spicule bundles, because light will leave the spicule bundles while being transferred between the subsequent single spicules. While transmitting light into the sponge body, the silica spicules in living Tethya aurantium specimens enable the growth and photosynthetic activity of putatively symbiotic microalgae in the most inner part of the sponge body.” (Brümmer et al. 2008:64)

Last Updated August 18, 2016

References

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