The role of cucurbitacins on the development of the polyphagous saltmarsh caterpillar (Estigmene acrea Drury) (Lepidoptera: Arctiidae)

In response to herbivory, plants produce specialized metabolites, which can negatively affect insect growth and reproduction by reducing food digestibility and/or impeding essential physiological processes. The impact of plant-produced defense metabolites on herbivore growth and reproduction depends on the degree of dietary specialization of herbivores. Generalist herbivores are often more vulnerable to plant defense metabolites, whereas specialists can detoxify or sequester and use them for protection against natural enemies. Plants of the gourd family (Cucurbitaceae) include several domesticated and wild species that produce a class of triterpenoid defense compounds, cucurbitacins, which mediate plant-herbivore interactions. Nevertheless, several domesticated cucurbit varieties have lost the ability to produce cucurbitacins or produce low levels. In this study, we will measure the levels of cucurbitacins produced by the domesticated plant species Cucurbita pepo and the wild species Cucurbita foetidissima and assess their impact on the development of the polyphagous saltmarsh caterpillar (Estigmene acrea, Drury) (Lepidoptera: Arctiidae). Saltmarsh caterpillars feed on more than 60 plant species of different families. They have been reported to sequester compounds such as iridoid glycosides and have shown the ability to adapt to pyrrolizidine alkaloids. Little is known about the effect of cucurbitacins on saltmarsh caterpillars. However, a recent study has shown that they could suppress defenses in zucchini plants by rendering neighboring plants more susceptible to subsequent saltmarsh caterpillar attack. Overall, this study aims to cast light on the plant chemical compounds that mediate the interactions of wild and domesticated species of the gourd family with E. acrea caterpillars.