Many Legs Provide Thrust for Burrowing

close up photograph of a rolled up red millipede

Biological Strategy

Millipedes

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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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Modify Position

Many resources that living systems require for survival and reproduction constantly change in quantity, quality, and location. The same is true of the threats that face living systems. As a result, living systems have strategies to maintain access to shifting resources and to avoid changing threats by adjusting their location or orientation. Some living systems modify their position by moving from one location to another. For those that can’t change location, such as trees, they modify position by shifting in place. An example of an organism that does both is the chameleon. This creature can move from place to place to find food or escape predators. But it also can stay in one place and rotate its eyes to provide a 360-degree view so that it can hunt without frightening its prey.

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Myriapods

Class Myriapoda (“many feet”): Centipedes and millipedes

The species in this class are defined by their feet. The name centipede means “one hundred feet” and millipede means “one thousand feet”. Although myriapods don’t have exactly 100 or 1000 legs, centipedes have one pair of legs per body segment while millipedes have two pairs per segment. Centipedes have a flattened body and are fast-moving carnivores who use venom to kill their prey. Millipedes, on the other hand, are rounder in shape and move slowly through soil to eat decaying plants. Both animals like to live in dark, moist environments that allow them to stay protected and hydrated.

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The many short legs of a millipede provide thrust for burrowing as the leg movements follow a wave along the body.

Image: Ghost Particle /

Image: Janice Carr / Centers for Disease Control and Prevention /

“A millipede advances along a twig. Although renowned for the number of their legs, even the longest millipedes have only about 680 legs, and most species have far fewer. You might expect that an animal with so many legs would move very fast, but the millipede’s legs are so short and its fat body so close to the ground that its legs take only short strides at a time. Nevertheless, they can deliver considerable thrust, and millipedes are strong enough to burrow into the ground very efficiently…The leg movement of the millipede occurs in a wave along the body: certain groups of legs are moving forwards as others are thrusting backwards. At any given time there are always some legs in contact with the ground at intervals along its body.” (Foy and Oxford Scientific Films 1982:45)

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Last Updated October 26, 2016

References

Book

The grand design: Form and colour in animals

26/02/1983 | Sally Foy

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