Antioxidant availability trades off with warning signals and toxin sequestration in the large milkweed bug (Oncopeltus fasciatus)
Heyworth HC, Pokharel P, Blount JD and others. Ecology and evolution, April 2023.
Read the paper Free to read · doi:10.1002/ece3.9971
What this paper is about
Warning coloration and chemical defence often go together, and one explanation is that both draw on the same limited resource. Large milkweed bugs need antioxidants both for their red pigment and to protect themselves from the toxins they store.
The authors tested whether the two uses compete, and found a trade-off between brightness and the ability to absorb toxin safely.
Summarised here from the abstract below. Not the authors’ words.
Abstract
In some aposematic species the conspicuousness of an individual's warning signal and the concentration of its chemical defense are positively correlated. Several mechanisms have been proposed to explain this phenomenon, including resource allocation trade-offs where the same limiting resource is needed to produce both the warning signal and chemical defense. Here, the large milkweed bug (Oncopeltus fasciatus: Heteroptera, Lygaeinae) was used to test whether allocation of antioxidants, that can impart color, trade against their availability to prevent self-damage caused by toxin sequestration. We investigated if (i) the sequestration of cardenolides is associated with costs in the form of changes in oxidative state; and (ii) oxidative state can affect the capacity of individuals to produce warning signals. We reared milkweed bugs on artificial diets with increasing quantities of cardenolides and examined how this affected signal quality (brightness and chroma) across different instars. We then related the expression of warning colors to the quantity of sequestered cardenolides and indicators of oxidative state-oxidative lipid damage (malondialdehyde), and two antioxidants: total superoxide dismutase and total glutathione. Bugs that sequestered more cardenolides had significantly lower levels of the antioxidant glutathione, and bugs with less total glutathione had less luminant orange warning signals and reduced chroma of their black patches compared to bugs with more glutathione. Bugs that sequestered more cardenolides also had reduced red-green chroma of their black patches that was unrelated to oxidative state. Our results give tentative support for a physiological cost of sequestration in milkweed bugs and a mechanistic link between antioxidant availability, sequestration, and warning signals.
Abstract reproduced from the published paper, which is licensed CC BY. Copyright remains with the authors.
Key terms
Milkweeds in this paper
- Red Milkweed Asclepias rubra
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"Antioxidant availability trades off with warning signals and toxin sequestration in the large milkweed bug (Oncopeltus fasciatus) (listing)." Milkweed USA, 2026, https://milkweedusa.com/research/antioxidant-availability-trades-off-with-warning-signals-and-toxin-2023/. Accessed DATE.
Milkweed USA. "Antioxidant availability trades off with warning signals and toxin sequestration in the large milkweed bug (Oncopeltus fasciatus) (listing)." Last modified 2026-08-01. Accessed DATE. https://milkweedusa.com/research/antioxidant-availability-trades-off-with-warning-signals-and-toxin-2023/.
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title = {Antioxidant availability trades off with warning signals and toxin sequestration in the large milkweed bug (Oncopeltus fasciatus) (listing)},
author = {{Milkweed USA}},
year = {2026},
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