Achieving Precise Alignment

an orange sea slug nestles into sand underwater

Biological Strategy

Rosy tritonia

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Image: Anthony Disbrow / Flickr / CC BY - Creative Commons Attribution alone

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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Sense Electricity/Magnetism From the Environment

Some living systems use electric or magnetic signals as a way to receive information from their environment. Magnetic and electric fields can help such living systems determine direction, altitude, or location, and electric fields also help living systems find other living systems. Detecting and interpreting electrical and magnetic signals requires specialized techniques. For example, mud-dwelling bacteria use crystals composed of magnetite to sense geomagnetism, which helps orient the bacteria to burrow deeper into the mud.

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Sense Balance/Orientation

Living systems must maneuver, remain in position, detect differences in weight, and find direction. This often requires more than visual cues, and so living systems have strategies for sensing balance and orientation from both internal and external cues. Once balance or orientation is detected, living systems must make the adjustments necessary to maintain position and direction. For example, sea slugs use neural mechanisms to detect and align themselves at an angle to the earth’s north-south magnetic axis.

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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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Sea slugs align themselves at a precise angle by detecting the Earth's north-south magnetic axis.

“Undersea creatures are also sensitive to magnetic pull. The sea slug (Tritonia diomeda), for instance, is known to align itself precisely at an angle of 87.6° east to the Earth’s north-south magnetic axis.” (Shuker 2001:46)

“Tritonia diomedea uses the Earth’s magnetic field as an orientation cue, but little is known about the neural mechanisms that underlie magnetic orientation behavior in this or other animals. Six large, individually identifiable neurons in the brain of Tritonia (left and right Pd5, Pd6, Pd7) are known to respond with altered electrical activity to changes in earth-strength magnetic fields. In this study we used immunochemical, electrophysiological, and neuroanatomical techniques to investigate the function of the Pd5 neurons, the largest magnetically responsive cells…Given that TPeps [neuropeptides isolated from Pd5] increase ciliary beating and Tritonia locomotes using pedal cilia, our results are consistent with the hypothesis that Pd5 neurons control or modulate the ciliary activity involved in crawling during orientation behavior.” (Cain et al. 2006:235)

Last Updated September 14, 2016

References

Book

The Hidden Powers of Animals: Uncovering the Secrets of Nature

26/02/2021 | Dr. Karl P. N. Shuker

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Reference

Journal article

Immunochemical and electrophysiological analyses of magnetically responsive neurons in the mollusc Tritonia diomedea

J Comp Physiol A | 20/10/2005 | Shaun D. Cain, John H. Wang, Kenneth J. Lohmann

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