Berberis sawfly contains toxic peptides not only at larval stage

Livestock can die from grazing in areas where larvae of certain Argidae or Pergidae species containing toxic peptides occur in mass. However, it remains unknown whether other stages also contain these compounds. Here, single specimens of larvae, prepupae, and adults of Arge berberidis , plus samples of its cocoons and larval feces, were analyzed by liquid chromatography-tandem mass spectrometry. The four peptides, pergidin (Perg), 4-valinepergidin (VPerg), dephosphorylated pergidin (dpPerg), and lophyrotomin (LGln), were detected in each of the three stages. Peptide concentrations, in percentage fresh weight, increased from larval up to adult stages, with mean values from 0.044 to 0.125% for Perg, 0.008 to 0.023% for VPerg, and 0.064 to 0.116% for LGln, whereas dpPerg never exceeded 0.001%. The concentrations of this latter peptide averaged 0.002% in the cocoon built by the prepupa, and nearly no peptides were detected in larval feces. Moreover, the concentrations of the three main peptides (Perg, LGln, and VPerg) tended to be correlated with each other in larvae and especially in adults. It is likely that peptide production, purportedly by an endosymbiont, stops at prepupal stage and that concentration of the peptides increases from prepupa to adult due to a decrease of body weight.