Head Bores Through Wood

a tightly composed photo shows small holes are seen in a piece of drift wood

Biological Strategy

Naval shipworm

AskNature Team

Image: Jon D. Anderson / Flickr / CC BY - Creative Commons Attribution alone

Move in/on Solids

To obtain needed resources or escape predators, some living systems must move on solid substances, some must move within them, and others must do both. Solids vary in their form; they can be soft or porous like leaves, sand, skin, and snow, or hard like rock, ice, or tree bark. Movement can involve a whole living system, such as an ostrich running across the ground or an earthworm burrowing through the soil. It can also involve just part of a living system, such as a mosquito poking its mouthparts into skin. Solids vary in smoothness, stickiness, moisture content, density, etc, each of which presents different challenges. As a result, living systems have adaptations to meet one, and sometimes multiple, challenges. For example, some insects must be able to hold onto both rough and slippery leaf surfaces due to the diversity in their environment.

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Physically Break Down Living Materials

Living materials are those that are part of living systems (whether currently or formerly alive). For example, a fallen log, although dead, is considered a living material. Breaking down or breaking up living materials is important for living systems that feed on them, as well as in facilitating the decomposition of organic matter. Breakdown increases the material’s surface area exposed to moisture, fungi, bacteria, and other living systems, many of which use enzymes and other chemicals to further break it down. But living materials can be difficult to break down because, for their own survival, their composition must provide support and protection. Therefore, living systems require mechanical means (such as grinding, tearing, or chewing) to manipulate these materials, as well as strong materials that can overcome resistance. For example, small beetles that chew through wood have large, strong jaws that enable them to cut through this tough material.

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Chemically Break Down Organic Compounds

The vast majority of biochemical assembly and breakdown processes–even by the most complex organisms–occur within cells. In fact, cells are able to perform hundreds, even thousands of chemical transformations at the same time under life-friendly conditions (ambient temperature and pressure in an aqueous environment). Part of the reason that decomposition reactions (chemical breakdown) can occur under such mild conditions is because most often, they occur in a stepwise, enzyme-mediated fashion, sipping or releasing small amounts of energy at each step. For example, the breakdown of glucose to pyruvate–and the release of energy–occurs in the 10-step enzyme catalyzed process of glycolysis.

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Bivalves

Class Bivalvia (“two-valved”): Clams, mussels, oysters

The bivalve name says it all: these animals are characterized by a two-sided shell that is connected at the hinge with a muscle. The 15,000 species in 90 families have flattened bodies, no head, and generally live a sedentary lifestyle. Instead of having a circular band of teeth like other molluscs, many are filter feeders. They use cilia, or hair-like extensions, to move water into their bodies and pluck out plankton to eat. Consequently, there are no terrestrial bivalves, and only 15% live in freshwater ecosystems. The rest live in marine environments.

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The head of a shipworm bores circular burrows in wood thanks to raspy, rotating shells.

Worm-like molluscs of the genus Teredo have been known to people for thousands of years because of their habit of wrecking wooden ships and piers. “There are many different types of shipworms, the largest of which is up to 2 metres long. The worm has a head with two shells (they do the damage), and a wormlike body that follows behind…They invade wood while in the tiny larval stage…The shipworm uses the shell on its head to burrow. Their ridged and rough surfaces rub the wood away as the worm first turns its head one way then the other. This cuts away a perfectly circular tube that is just a bit larger than the shell itself. The worm then eats the wood it has cut away, turning the in the wood into that it uses for energy. The wormlike body follows behind the shell, producing a substance like chalk to line the burrow…The worm gets its oxygen from water. It draws the water in then passes it out again through through two tubes on its tail called siphons. These stick out from the opening of the burrow but can be pulled in and the burrow closed by special small plates called pallets. These seal the tube so tightly that shipworms can survive when the timber is temporarily out of water.” (Liverpool Museum 2008)

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