Skin Detects Thermal Signals

gray sharks with black tips on their dorsal fins swim in clear blue water

Biological Strategy

AskNature Team

Image: Doug Finney / Flickr / CC BY - Creative Commons Attribution alone

Sense Temperature Cues From the Environment

Some living systems use their ability to perceive temperature to find prey or avoid predators, or as a way to gain information about their environment, such as whether they are near a warm or cold place. Temperature gradients can be subtle and modulate as they travel through water, air, or solids. Living organisms must therefore have a variety of thermal sensors appropriate to a given medium (liquid, gas, solid). Some even have a way to “visualize” a signal’s source. For example, the rattlesnake has heat sensors with thousands of nerve endings located in pit-shaped holes on each side of its face. The sensitivity of the pits overlaps, giving the snake a bifocal image of the heat’s source.

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Fish

Class Agnatha (“without jaws”), Class Chondrichthyes (“cartilage fish”), Superclass Osteichthyes (“bone fish”): Sharks, eels, snapper, hagfish

The fish are a diverse group, comprising multiple classes within Phylum Animalia. The most well-known classes are Chondrichthyes, which has sharks and rays, and superclass Osteichthyes, which has all bony fish like cod and tuna. Unlike other vertebrates, fish only live in water. They use special adaptations like fins, gills, and swim bladders to survive. Most are ectothermic, meaning their body temperature depends on the water temperature around them. Over half of all vertebrates are fish. They’re found from the bottom of the sea to high mountain lakes.

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The skin of the blacktip reef shark enables it to locate prey via a gel that detects thermoelectric signals.

Image: Luc Viatour / Wikimedia commons /

Image: Klaus Stiefel /

“[T]he thermoelectric properties of an extracellular gel… from the electrosensors of sharks… develops significant voltages in response to tiny temperature gradients. This bulk property of the gel indicates that temperature can be translated into electrical information without the need for ion channels, a sensitivity that may help sharks to locate thermal fronts as feeding areas.” (Brown 2003:495)

Last Updated August 18, 2016

References

Journal article

Neurophysiology: Sensing temperature without ion channels

Nature | 09/07/2008 | Brandon R. Brown

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Reference

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