Locomotion in Invertebrates


The invertebrates utilize a diversity of mechanisms to move. This diversity is evident by examining the variety of arrangements of muscles found within the skeletal system, and the structure of the components comprising the skeletal support system itself.

Keywords: invertebrates; locomotion; walking; swimming; flying

Figure 1.

A muscular‐hydrostatic support system – the mantle of the squid. The arrangement of the circular and radial muscles is shown. The circular muscles are arranged around the circumference. Contraction of these muscles decreases the diameter of the mantle and propels water out of the mantle cavity. During rapid escape responses, contraction of the radial muscles, which run from the inside of the mantle to the outside, increases the rate at which the mantle refills. The collagenous fibres, which are found throughout the mantle in highly organized arrangements, are also shown. (From Gosline and DeMont, 1985.)

Figure 2.

The muscles and tendons used when a locust jumps. Prior to jumping both the extensor and flexor muscles contract, and during this time the flexor muscle stores elastic strain energy in both the semilunar process and the extensor tendon. The animal jumps by suddenly relaxing the flexor muscle, which releases the energy stored elastically and powers the jump. (From Alexander, 1992.)

Figure 3.

The three mechanisms used by a fruitfly to develop aerodynamic lift. The three panels show the prominent aerodynamic force during each phase of the wing stroke: delayed stall occurs during most of the wing stroke (1), while at the end of the stroke the wing rotates providing a rotational lift (2, 3, 4), and at the start of the upstroke the wing captures the wake to produce an additional force (5). (From Dickinson, 2001.)


Further Reading

Alexander R McN (1990) Animals. New York: Cambridge University Press.

Alexander R McN (1992) Exploring Biomechanics – Animals in Motion. New York: Scientific American Library.

Delcomyn F (1977) Co‐ordination of invertebrate locomotion. In: Alexander R McN and Goldspink G (eds) Mechanics and Energetics of Animal Locomotion. New York: John Wiley.

DeMont ME (1992) Locomotion of soft bodied animals. In: Alexander R McN (ed.) Advances in Comparative Environmental Physiology 11 – Mechanics of Animal Locomotion, pp. 67–185. New York: Springer‐Verlag.

Dickinson M (2001) Solving the mystery of insect flight. Scientific American 284: 48–57.

Gosline JM and DeMont ME (1985) Jet‐propelled swimming in squids. Scientific American 252: 96–103.

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DeMont, M Edwin, Ford, Matthew D, and Mitchell, Sean C(May 2005) Locomotion in Invertebrates. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1038/npg.els.0003641]