Anti-predator chemical defence in the mountain katydid (Acripeza reticulata)

Abstract

Chemical defences are an anti-predatory strategy involving the accumulation of compounds that case harm, discomfort or are unpalatable to predators. Many chemical defences are acquired through sequestration, in which plant secondary metabolites are consumed by tolerant prey and repurposed for prey defences. The mountain katydid (Acripeza reticulata) is a putatively chemically defended insect which exhibits a deimatic display. Traditionally, deimatism is considered to be a bluff, however this definition would be challenged if the mountain katydid possessed a true chemical defence. In this study I aimed to determine if compounds associated with chemical defences were found in the mountain katydid's abdominal exudate. I analysed this exudate, as well as katydid regurgitate, faeces and Senecio diet using gas-chromatography mass-spectrometry (GC-MS). In both the abdominal exudate and the Senecio plants I detected pyrrolizidine alkaloids (PAs) - chemical defence compounds found in many insect and plant species. The types of PA present were not significantly different between the plant and the exudate, and PAs were generally not excreted through the katydid's faeces, suggesting that sequestration was occurring. Future studies on the katydid's chemical defence would require the identification of the PAs in both the Senecio diet, and the exudate. Finally, taste aversion experiments are necessary to definitively determine if the function of these PAs is indeed chemical defence.

Date of Award	2019
Original language	English