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Insects had it first: surfactants as a defence against predators
Michael Rostás1, Katrin Blassmann
1Department of Botany II, Institute for Biological Sciences, University of Würzburg, Julius-von-Sachs-Platz-3, 97082 Würzburg, Germany.
Proceedings. Biological Sciences
|November 7, 2008
Summary
Insect oral secretions (OS) use detergent properties, not just plant toxins, to repel predators. This surfactant defense mechanism helps insects like Spodoptera exigua protect themselves from ant attacks.
Area of Science:
- Entomology
- Chemical Ecology
- Animal Behavior
Background:
- Insects utilize oral secretions (OS) as a defense against predators.
- The defensive properties of OS have been attributed to plant-derived secondary metabolites.
- This traditional view presents challenges for generalist herbivores on low-metabolite plants.
Purpose of the Study:
- To investigate a novel defense mechanism in insect OS independent of plant-derived deterrents.
- To determine if the intrinsic properties of OS contribute to predator deterrence.
- To explore the role of surfactants in insect defense strategies.
Main Methods:
- Analysis of the amphiphilic and wetting properties of Spodoptera exigua OS.
- Observation of ant behavior (e.g., cleansing) upon contact with insect OS.
- Assessment of the defensive efficacy of OS surfactants against predatory ants.
Main Results:
- Insect OS, particularly from Spodoptera exigua, exhibits high amphiphilicity.
- The OS effectively wets the hydrophobic cuticle of predatory ants, disrupting their attack.
- Ants exposed to OS engaged in extensive self-cleansing behaviors, indicating deterrence.
- The presence of surfactants in OS was sufficient to explain its defensive action.
Conclusions:
- Insect OS possesses intrinsic detergent properties that serve as a defense mechanism against predators.
- This detergency is a potentially common, yet unrecognized, mode of insect defense.
- Insects evolved the use of defensive surfactants independently, predating their agricultural application.
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