Single-insect NMR: A new tool to probe chemical biodiversity

Because of analytical limitations, multiple animals or plants are typically required to identify natural products. Using a unique 1-mm high-temperature superconducting NMR probe, we directly examined the chemical composition of defensive secretions from walking stick insects. Individual milkings were dissolved in D2O without purification and examined by NMR within 10 min of secretion. We found that Anisomorpha buprestoides secretes similar quantities of glucose and mixtures of monoterpene dialdehydes that are stereoisomers of dolichodial. Different individual animals produce different stereoisomeric mixtures, the ratio of which varies between individual animals raised in the same container and fed the same food. Another walking stick, Peruphasma schultei, also secretes glucose and a single, unique stereoisomer that we are naming peruphasmal. These observations suggest a previously unrecognized significance of aqueous components in walking stick defensive sprays. Single-insect variability of venom demonstrates the potential importance of chemical biodiversity at the level of individual animals.