Hind Legs Maximize Swimming Efficiency

close up photograph of dark brown beetle swimming in water

Biological Strategy

Whirligig beetles

AskNature Team

Image: Agami Photo Agency / Shutterstock / Some rights reserved

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.

Search this Function

Distribute Energy

Many forms of energy are naturally available, including kinetic, potential, thermal, elastic, radiant, chemical, and more. All living systems require energy to carry out their many activities. Energy isn’t a physical object that can be held, so it also can’t be pushed, pulled, or carried. However, it can be transmitted or transformed. For example, the golden-scale snail has a tri-layered shell that dissipates, or transfers, forces from a predator biting down on it, thereby minimizing damage to its soft body inside the shell.

Search this Function

Move in/on Liquids

Water is not only the most abundant liquid on earth, but it’s vital to life–so it’s no surprise that the majority of life has evolved to thrive on and under its surface. Moving efficiently in and on this dense and dynamic substance presents unique challenges and opportunities for living systems. As a result, they have evolved countless solutions to optimize drag, utilize surface tension, fine tune buoyancy, and take advantage of various types of currents and fluid dynamics. For example, sharks can slide through water by reducing drag due to their streamlined shape and specially shaped features on their skin.

Search this Function

Insects

Class Insecta (“an insect”): Flies, ants, beetles, cockroaches, fleas, dragonflies

Insects are the most abundant arthropods—they make up 90% of the animals in the phylum. They’re found everywhere on earth except the deep ocean, and scientists estimate there are millions of insects not yet described. Most live on land, but many live in freshwater or saltwater marshes for part of their life cycles. Insects have three distinct body sections: a head, which has specialized mouthparts, a thorax, which has jointed legs, and an abdomen. They have well-developed nervous and sensory systems, and are the only invertebrate that can fly, thanks to their lightweight exoskeletons and small size.

Search this Living System

The hind legs of the whirligig beetle maximize swimming speed and minimize energy use by beating in an alternating stroke pattern.

The whirligig beetle can swim quickly atop water. Although it can attain its highest speeds by simultaneously beating its hind legs together, this movement is too energetically costly to maintain over great distances. In comparison, alternately beating its hind legs allows the whirligig beetle to reach comparable, though slightly slower, speeds while conserving enough energy to maintain those speeds over longer distances.

This alternate beating causes the beetle to move in an S-shaped trajectory instead of a linear one, which also helps it avoid predators due to its unpredictable pattern of movement.

This strategy was contributed by Rachel Major

Last Updated August 23, 2016

References

Journal article

Experimental Studies and Dynamics Modeling Analysis of the Swimming and Diving of Whirligig Beetles (Coleoptera: Gyrinidae)

PLoS Comput Biol | 29/11/2012 | Zhonghua Xu, Scott C. Lenaghan, Benjamin E. Reese, Xinghua Jia, Mingjun Zhang |

Philip R. LeDuc

embedly preview

AskNature