Shelters Constructed Underwater

photograph of white, blue, purple and orange sea worm against black background

Biological Strategy

Sandcastle worm

AskNature Team

Image: LA Urban Ocean Expedition Staff / Flickr / Some rights reserved

Physically Assemble Structure

Living systems use physical materials to create structures to serve as protection, insulation, and other purposes. These structures can be internal (within or attached to the system itself), such as cell membranes, shells, and fur. They can also be external (detached), such as nests, burrows, cocoons, or webs. Because physical materials are limited and the energy required to gather and create new structures is costly, living systems must use both conservatively. Therefore, they optimize the structures’ size, weight, and density. For example, weaver birds use two types of vegetation to create their nests: strong, a few stiff fibers and numerous thin fibers. Combined, they make a strong, yet flexible, nest. An example of an internal structure is a bird’s bone. The bone is comprised of a mineral matrix assembled to create strong cross-supports and a tubular outer surface filled with air to minimize weight.

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Attach Permanently

A living system can conserve energy by attaching permanently to a particular site because it can take advantage of resources that come its way, rather than expending energy to move to resources. A permanent attachment, intended to last the lifetime of the living system, creates special challenges. For example, physical mechanisms, such as the anchor that holds a marine algae to the ocean’s bottom, must be able to withstand forces that can pull it off its substrate. Chemical mechanisms, such as a barnacle’s glue, must avoid both physical and chemical breakdown, such as being dissolved by water.

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Animals

Kingdom Animalia (“having breath or soul”): Mammals, reptiles, sponges, corals, insects, birds

This kingdom captures a staggering variety of life—from the smallest coral polyp to the largest elephant. Although animal body shapes and life histories vary, there are a few defining characteristics. Animals are heterotrophs, meaning they gain energy from eating other organisms, and have developed from single-celled ancestors to highly diversified and coordinated multicellular forms. Unlike plant and fungi cells that have rigid cell walls, animal cells are bound by more flexible combinations of proteins. Most animals have cells organized into tissues and are able to move within their environment.

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Tube-like shelters of sandcastle worms are constructed from mineral particles using an underwater, quick-set glue.

“Phragmatopoma californica, also called the Sandcastle worm, is a polychaete…which lives in intertidal zones off the coast of California. The worm deploys a crown of ciliated tentacles for capturing and transporting food and particulates from the water column to its mouth where the captured materials are evaluated with ciliated lips. Food is ingested, unsuitable particles are cast away, while particles judged to be of the right size, shape, composition, and surface chemistry for incorporation into the tube are passed to a pair of dexterous palps, the so-called building organ, located immediately ventral to the mouth. Two minute spots of proteinaceous adhesive are applied before the particles are pressed into place by the building organ onto the end of the tube. The worm wriggles the newly placed particles until the adhesive sets, which takes less than 30 s under cold salty water [3].” (Endrizzi & Stewart 2009:547)

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