Resistance to plant toxins in milkweed butterflies is linked to toxin storage for defense

A monarch caterpillar feeding on milkweed (Credit: OakleyOriginals. CC BY 2.0)
A monarch caterpillar feeding on milkweed (Credit: OakleyOriginals. CC BY 2.0)

When your only food source also contains a deadly poison, your options are pretty limited: either find a new food source or find some way of making the poison less toxic. This is exactly the situation that many plant-eating insects find themselves in, particularly those that eat milkweed.

Milkweeds produce a class of chemical toxins named cardenolides. These compounds specifically bind and inhibit the sodium potassium pumps found in heart muscle cells. Without working pumps sodium levels in the cell rise, setting off a chain of events that ultimately disrupt muscle contraction in cardiac tissue. At a high enough dose, these heart-stimulating effects can be lethal to insects, humans and animals in between. How then do insects that depend on milkweed as their main food source cope with this hidden poison? Continue reading

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