Response of the lichen-eating moth Cleorodes lichenaria larvae to varying amounts of usnic acid in the lichens

Abstract

Lichens are characterized by a great variety of secondary metabolites. The function of these substances remains partly unknown. In this study, we propose that some of these metabolites may expel insect herbivores. To test this hypothesis, we reared larvae of the lichenivorous moth Cleorodes lichenaria on three selected lichens, Cladonia arbuscula subsp. mitis, Usnea hirta, and Usnea dasypoga. In experimental setup, the secondary metabolite usnic acid was removed from the lichens with acetone prior to feeding, whereas a control was left untreated. On all three lichens, removal of usnic acid from the lichens using acetone significantly prolonged survival of larvae and increased their viability. Larvae reared on control lichens contained significantly more usnic acid than those reared on treated lichens, both in their biomass and their faeces. These results support the hypothesis that usnic acid serves as a repellent against insect feeding, besides its well established functions of UV protection and antimicrobial properties.

Which Specialized Metabolites Does the Native Subantarctic Gastropod Notodiscus hookeri Extract from the Consumption of the Lichens Usnea taylorii and Pseudocyphellaria crocata?

“…As to this latter point, usnic acid exhibited an acute toxicity against larvae of the polyphagous insect herbivore Spodoptera littoralis with a LD 50 at 8.6 µM for (−)-usnic acid and 90.8 µM for (+)-usnic acid [ 25 ] as well as towards the larvae of the house mosquito Culex pipiens with a dose-dependent larval mortality [ 26 ]. Likewise, a recent study reported on the detrimental effects of usnic acid on the growth and survival rate of the larvae of the lichen-eating moth Cleorodes lichenaria [ 27 ]. Harmful effects of usnic acid were also demonstrated on vertebrate herbivores.…”

Overcoming Deterrent Metabolites by Gaining Essential Nutrients: A Lichen/Snail Case Study

“…Generalist lichenophages species generally preferred lichens with few secondary metabolites (Benesperi and Tretiach, 2004;Boch et al, 2015;Černajová and Svoboda, 2014;Gauslaa, 2005;Goga et al, 2015) but, more than the total amount of metabolites, the nature of the latter turns out to be the main discriminant factor in food preference by lichenophages. In the accidental degradation of the lichen herbarium of the Trieste University, the coleopteran Lasioderma serricorne avoided lichen species containing the dibenzofurane usnic acid, the depside atranorin or the depsidone fumarprotocetraric acid (Nimis and Skert, 2006).…”

Overcoming deterrent metabolites by gaining essential nutrients: A lichen/snail case study

“…Generalist lichenophage species prefer lichens with few specialised metabolites (Benesperi and Tretiach, 2004;Boch et al, 2015;Černajová and Svoboda, 2014;Gauslaa, 2005;Goga et al, 2015), but more than the total amount of metabolites, their nature turns out to be the main discriminant factor in food preference. In the accidental degradation of the lichen herbarium of the Trieste University, the coleopteran Lasioderma serricorne avoided lichen species containing the dibenzofuran usnic acid, the depside atranorin or the depsidone fumarprotocetraric acid (Nimis and Skert, 2006).…”