TAG: GS 3: ECOLOGY AND ENVIRONMENT
THE CONTEXT: Caterpillars possess an extraordinary ability known as electroreception, allowing them to sense electric fields around them.
EXPLANATION:
- This discovery, made by British researchers and published in the Proceedings of the National Academy of Sciences.
- It is revealed that caterpillars use small bristles called setae on their bodies to detect electric fields, a sensory ability that most land-based animals lack.
Highlights of the research
- Researchers conducted laboratory experiments on four species of caterpillars: the cinnabar moth, the scarce vapourer moth, the European peacock butterfly, and the common wasp.
- These experiments aimed to explore how these caterpillars utilize electroreception to detect potential threats from predators.
- To test their hypothesis, researchers used a live electrode carrying a voltage oscillating at 180 Hz to simulate the approach of a predatory wasp.
- When exposed to this electric field, the caterpillars exhibited stress behaviors such as flailing and coiling.
- In contrast, caterpillars near an electrode without voltage did not display these stress behaviors.
- This indicates that the caterpillars’ setae are responsive to electric fields that mimic the presence of predatory insects.
- The caterpillars’ setae were found to respond to electric field frequencies ranging from 50 to 350 Hz.
- The setae vibrated most intensely at a frequency of 220.3 Hz, which is close to the wingbeat frequency of many predator insects.
- It is suggested that caterpillars might have evolved to tune their sensory organs to the specific wingbeat frequencies of their predators.
- This evolutionary adaptation would provide a significant survival advantage.
Cinnabar moth (Tyria jacobaeae) caterpillar
Electroreception
- Electroreception is a well-known sensory ability among aquatic and amphibious animals, which they use to detect predators and prey.
- Since 2013, scientists have also identified this ability in certain arthropods, including bumblebees, hoverflies, and spiders.
- However, none of these land-based arthropods have been known to use electroreception as a defense mechanism against predators until now.
- While electroreception is a crucial sensory ability, caterpillars do not rely on it exclusively to detect predators.
- Electroreception supplements the caterpillars’ other senses, providing an additional layer of protection against threats.
Mechanism of Electroreception in Caterpillars
- Caterpillars use their setae to sense electric fields in a manner analogous to the interaction between a rubber balloon and human hair.
- When a balloon is rubbed against hair, static charges accumulate on both surfaces, leading to mutual electrostatic attraction and movement without direct contact.
- Similarly, as an insect’s wings flap, static charges build up on them.
- When such an insect approaches a caterpillar, the setae on the caterpillar’s body detect these charges by accumulating charges of their own.
- This interaction creates an oscillating electric field that the caterpillar can sense.
Potential Challenges: Sensory Pollution
- One potential challenge to caterpillars’ electroreception is sensory pollution.
- The setae are sensitive to voltage frequencies present in overhead power cables, which operate around 50-60 Hz.
- Exposure to these frequencies could desensitize the setae, diminishing the caterpillars’ ability to detect predators.
- This “sensory pollution” represents an environmental factor that could negatively impact the caterpillars’ survival.