A new and unexpected survivor of Aristolochia toxicity?

Abstract

Aristolochia plants (family Aristolochiaceae) are made toxic by secondary metabolites, some of which are carcinogenic to vertebrates (J Chromatogr A 2006; https://doi.org/10.1016/j.chroma.2005.12.072). Certain secondary metabolites, specifically aristolochic acids (AAs), are important defense compounds against herbivory. However, caterpillars from some tribes of swallowtail butterflies (family Papilionidae)—namely, tribes Luehdorfiini, Troidini, and Zerynthiini—are known to feed exclusively on Aristolochia foliage and to sequester these metabolites, thereby becoming toxic to predators (Annu Rev Entomol 2002; https://doi.org/10.1146/annurev.ento.47.091201.145121).

In the Parque Estadual de Itaúnas (within the Espírito Santo state of Brazil), we recently observed a land snail (Auris sp) consuming Aristolochia zebrina. The snail was observed rasping (scraping its tongue along) leaves of A zebrina, and numerous other leaves showed signs of herbivory, possibly indicating that this particular snail fed exclusively on this plant, as no other animals were detected feeding on it. We have been monitoring this State Park for several years, and intriguingly, leaf herbivory by Papilionidae larvae has never been detected on A zebrina.