Spicules Are Rigid Structural Materials

underwater photograph of sea sponges and a starfish

Biological Strategy

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Manage Compression

When a living system is under compression, there is a force pushing on it, like a chair with a person sitting on it. When evenly applied to all sides of a living system, compression results in decreased volume. When applied on two sides, it results in deformation, such as when pushing on two sides of a balloon. This deformation can be temporary or permanent. Because living systems must retain their most efficient form, they must ensure that any deformation is temporary. Managing compression also provides an opportunity to lessen the effects of other forces. Living systems have strategies to help prevent compression or recover from it, while maintaining function. For example, African elephant adults weigh from 4,700 to 6,048 kilograms. Because they must hold all of that weight on their four feet, the tissues of their feet have features that enable compression to absorb and distribute forces.

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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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The spicules of sponges are rigid structural materials due to their mineralized composition.

Image: Hannes Grobe/AWI / Wikimedia commons /

Microfossils from marine sediments-sponge spicule

Image: Zeichner (NOAA) / Wikimedia commons /

Microscopic Spiculesfrom Pachastrellid Sponge

Image: Ernest Russell Crutcher /

Sponge Spicules Grantia, Transmitted Circular Polarized Light

“There are yet other rigid materials, what Wainwright et al. (1976) refer to as ‘stony materials’ and Vincent (1990) calls ‘biological ceramics.’ These are distinguished by being very heavily mineralized, with more mineral (some inorganic salt) than organic matter. Some are tiny, such as the spicules of even very large sponges–made mainly of either calcium carbonate or silica (roughly, glass). Others occur in massive pieces, such as the skeletons of the stony corals and the shells of most mollusks, both made of calcium carbonate with a small amount of organic matter…On the general matter of what occurs where and how it’s put together, Brown (1975) remains a useful source.” (Vogel 2003:305)

Vogel S. Comparative Biomechanics: Life’s Physical World. Princeton: Princeton University Press; 2003. 580 p.

Last Updated October 26, 2016

References

Book

Comparative Biomechanics: Life's Physical World, Second Edition

Princeton University Press | 17/06/2013 | Steven Vogel

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