Threads Adhere Underwater

underwater photograph of echinoderm secreting white strings

Biological Strategy

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Image: Klaus Stiefel / Flickr / Some rights reserved

Attach Temporarily

Living systems must sometimes, temporarily, stay in one place, climb or otherwise move around, or hold things together. This entails attaching temporarily with the ability to release, which minimizes energy and material use. Some living systems repeatedly attach, detach, and reattach for an extended time, such as over their lifetimes. Despite being temporary, these attachments must withstand physical and other forces until they have achieved their purpose. Therefore, living systems have adapted attachment mechanisms optimized for the amount of time or number of times they must be used. An example is the gecko, which climbs walls by attaching its toes for less than a second. Other examples include insects that attach their eggs to a leaf until they hatch, and insects whose wings temporarily attach during flight but separate after landing.

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Protect From Animals

Animals–organisms that range from microscopic to larger than a bus–embody a wide variety of harms to living systems, including other animals. They threaten through predation, herbivory, defense, and parasitism, and they compete for resources such as water, nutrients, and space. Any given living organism commonly faces threats from a variety of animals, requiring strategies that effectively defend from each. Trout and other bony fish, for example, escape predators by having scales made of very thin, flake-like pieces of bone covered with slippery mucus. They also have behavioral strategies such as camouflage, fast swimming, and twisting and turning to achieve release from a predator’s grip.

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Gastropods

Class Gastropoda (“stomach-foot”): Snails and slugs

There are at least 40,000 known species of gastropod, with many more yet to be discovered, making it the largest class of mollusks. These animals exhibit torsion, meaning their internal organs are twisted 180° during development. The majority of gastropods have shells, and most open up on the right side. The largest gastropods are the size of a small child (3 feet, or 1 meter) while the smallest are barely visible to the naked eye.

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Sticky ejectable threads of sea cucumbers adhere underwater and cure quickly because as the outer cell layer is shed, the inner cell layer springs open, elongates, and secretes granules of insoluble proteins that stick together.

“Patrick Flammang of the University of Mons, Belgium, is studying the sea cucumber. The sea cucumber, a relative of the starfish, protects itself from predators by ejecting, in a matter of seconds, fine, sticky threads that entangle an attacker and enable the sea cucumber to sneak away. Before they are ejected, the threads, which consist of an outer and inner layer of cells, are quite short and not sticky. But as they are ejected, the emerging threads shed their outer cell layer, enabling the inner cell layer to spring open and elongate. At the same time, the inner cells secrete granules of insoluble proteins that stick together and adhere to whatever they come in contact with in the water. Such quick-drying, underwater glues may be alternatives to existing marine adhesives which take longer to cure.” (Courtesy of the Biomimicry Guild)

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