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Defensive steroids from a carrion beetle (Silpha americana)
Experientia
|April 15, 1985
Summary
Silpha americana beetles release defensive steroids from their rectum when disturbed. Two of these steroids, 15 beta-hydroxyprogesterone and 5 beta-pregnan-16 alpha-ol-3,20-dione, deter feeding in jumping spiders.
Area of Science:
- Entomology
- Chemical Ecology
- Insect Defense Mechanisms
Background:
- Silpha americana, a carrion beetle, utilizes defensive secretions for protection.
- The anal effluent of insects can contain a diverse array of chemical compounds.
- Steroids are known signaling molecules in various biological contexts.
Purpose of the Study:
- To identify and characterize the chemical composition of the defensive anal effluent of Silpha americana.
- To investigate the potential defensive roles of these compounds against predators.
Main Methods:
- Gas chromatography-mass spectrometry (GC-MS) for compound identification.
- Nuclear magnetic resonance (NMR) spectroscopy for structural elucidation.
- Predator bioassays using jumping spiders (Araneae: Salticidae).
Main Results:
- The defensive effluent contains a mixture of seven steroid compounds, with 15 beta-hydroxyprogesterone as the principal component.
- None of the identified steroids have been previously reported in insects.
- Compounds 1 (15 beta-hydroxyprogesterone) and 6 (5 beta-pregnan-16 alpha-ol-3,20-dione) exhibited feeding deterrent properties against jumping spiders at a 1 microgram dosage.
Conclusions:
- Silpha americana employs a novel class of steroid compounds for defense.
- These steroids act as feeding deterrents, suggesting a role in predator avoidance.
- The findings expand the known repertoire of chemical defenses in insects.