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Cardenolides in the defensive fluid of adult large milkweed bugs have differential potency on vertebrate and invertebrate predator Na+/K+¬–ATPases
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  • Paola Rubiano-Buitrago,
  • Shrikant Pradhan,
  • Alfonso Aceves-Aparicio,
  • Shabnam Mohammadi,
  • Christian Paetz,
  • Hannah Rowland
Paola Rubiano-Buitrago
Max-Planck-Institut für chemische Ökologie

Corresponding Author:[email protected]

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Shrikant Pradhan
Max-Planck-Institut für chemische Ökologie
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Alfonso Aceves-Aparicio
Max-Planck-Institut für chemische Ökologie
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Shabnam Mohammadi
Max-Planck-Institut fur chemische Okologie
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Christian Paetz
Max-Planck-Institut für chemische Ökologie
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Hannah Rowland
Max-Planck-Institut fur chemische Okologie
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Abstract

The defences of aposematic animals are characterised by diversity and variability of secondary metabolites. Here we examine the nature and function of chemical defence diversity in large milkweed bugs, Oncopeltus fasciatus, testing the hypothesis that different chemical defence compounds have evolved in response to different enemies. We profiled and quantified the cardenolides sequestered by large milkweed bugs in their defensive secretions and their bodies, and measured the inhibitory properties of a subset of isolated milkweed cardenolides in the insect’s defence against the Na+/K+—ATPase target site of vertebrate and invertebrate predators, using porcine Na+/K+—ATPase data as a reference. We show that highly concentrated coroglaucigenin cardenolides in the insect’s defence (glucopyranosyl frugoside and frugoside) are toxic for both resistant and sensitive predators, whereas corotoxigenin and calotropagenin cardenolides have varying degrees of enzyme inhibition among various predators. Overall, O. fasciatus is well defended against a range of enemies due to the differential effect of these compounds´ target sites. Our results suggest that the compounds the insect sequester have evolved in response to predation pressure.