Pyrrolizidine alkaloids and pentacyclic triterpene saponins in the defensive secretions of Platyphora leaf beetles

Abstract

Field collected exocrine defensive secretions of nine neotropical Platyphora species were analyzed for the presence of plant acquired pyrrolizidine alkaloids (PAs) and pentacyclic triterpene saponins. All species secrete saponins. In addition, five species feeding on Tournefortia (Boraginaceae), Koanophyllon (Asteraceae, tribe Eupatorieae) and Prestonia (Apocynaceae) were shown to sequester PAs of the lycopsamine type, which are characteristic for species of the three plant families. The PA sequestering species commonly store intermedine, lycopsamine and their O 3% -acetyl or propionyl esters as well as O 7 -and O 9 -hydroxyisovaleryl esters of retronecine. The latter as well as the O 3% -acyl esters were not found in the beetles' host plants, suggesting the ability of the beetles to esterify plant derived retronecine and intermedine or its stereoisomers. Despite the conformity of the beetles' PA patterns, considerable inconsistencies exist regarding the PA patterns of the respective host plants. One host plant was devoid of PAs, while another contained only simple necines. Since the previous history of the field collected beetles was unknown this discrepancy remains obscure. In contrast to the Palearctic chrysomeline leaf beetles, e.g. some Oreina species which ingest and store PAs as their non-toxic N-oxides, Platyphora leaf beetles absorb and store PAs as the toxic free base (tertiary PA), but apparently avoid to accumulate PAs in the haemolymph. This suggests that Chrysolina and Platyphora leaf beetles developed different lines of adaptations in their parallel evolution of PA mediated chemical defense.

Detoxification of pyrrolizidine alkaloids by the harvestman Mitopus morio (Phalangidae) a predator of alkaloid defended leaf beetles

“…This chemical defense is primarily autogenous by cardenolides synthesized from plant acquired sterols (van Oycke et al 1987;Dobler et al 1996;Pasteels et al 1996). Only a few Oreina species (e.g.…”

Pyrrolizidine Alkaloids in the Pericopine MothScearctia figulina(Erebidae: Arctiinae): Metabolism and Chemical Defense

“…In PA specialist leaf beetles, such as Longitarsus and Platyphora species, dihydropyrrolizines are not present, and these beetles show 7S PAs sequestered from their host plants, even if some epimerization to 7R does occur. 37,38 However, in S. figulina we did not find an androconial organ that produces pheromones. It is suggesting that epimerization in S. figulina might be due to a phylogenetic constraint, since the more basal species Amerila spp.…”

How to Spoil the Taste of Insect Prey? A Novel Feeding Deterrent against Ants Released by Larvae of the Alder Leaf Beetle, Agelastica alni

“…[43,44] The biogenesis of isoxazolinone derivatives released by several adult Chrysomelinae species is also known to be based on amino acids, in this case aspartic acid. [45] Interestingly, the defensive glandular secretions of several adult Chrysomelinae species also contain cardenolides or pyrrolizidine alkaloids in addition to amino acid derivatives, [10,46] but we did not detect any of these compounds in the investigated fluid.…”