A new study in Ecology Letters has discovered that monarch butterflies employ medicinal plants to treat their larva. Researchers found that certain species of milkweed, which the larva feed on, can reduce the threat of a sometime deadly parasite. However, even more surprising: “we have also found that infected female butterflies prefer to lay their eggs on plants that will make their offspring less sick, suggesting that monarchs have evolved the ability to medicate their offspring,” says lead author Jaap de Roode.
According to de Roode this is the best evidence yet of animals employing medication to prevent or cure disease.
“The results are also exciting because the behavior is trans-generational,” Thierry Lefevre, a member of de Roode’s lab, said. “While the mother is expressing the behavior, only her offspring benefit. That finding is surprising for monarch butterflies.”
When monarch butterfly larva feed on certain species of milkweed they consume a chemical known as cardenolides, which can kill a bothersome gut parasite in the butterflies known as Ophryocystis elektroscirrha. This parasite can hurt a butterfly’s ability to fly, shorten their life-span, and in worse-case-scenarios outright kill them. Since female butterflies pass the parasite on to their offspring, researchers wondered if infected monarch mothers would act on the disease. Proving their hypothesis: in lab tests de Roode discovered that infected mothers preferred to lay their eggs on milkweed with the toxic cardenolides, while those unaffected with the parasite were ambivalent.
The researchers say that studying how animals utilize medicinal compounds in their surroundings could lead humans to discover new drugs.
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