In an Emory University blog called eScience
, de Roode said
"We have shown that some species of milkweed, the larva’s food plants, can reduce parasite infection in the monarchs. And we have also found that infected female butterflies prefer to lay their egg on plants that will make their offspring less sick, suggesting that monarchs have evolved the ability to medicate their offspring.
We believe that our experiments provide the best evidence to date that animals use medication."
de Roode noted that the team found females not infected with the parasite do not lay their eggs on the species of plants that help the butterflies fight the infestation.
de Roode, who has been given $500,000 for more in-depth studies of how Monarchs use medicinal plants, saying there has been little research into "self-medication by animals."
de Roode was the lead researcher on a four person research team, and their paper Evidence for trans-generational medication in nature
, which details their findings, was published in the journal, Ecology Letters.
In a press release
issued Monday, one of the team's researchers, Thierry Lefevre said
"The results are also exciting because the behavior is trans-generational. While the mother is expressing the behavior, only her offspring benefit. That finding is surprising for monarch butterflies."
Another of the researchers, ecologist Mark Hunter, stressed the lack of knowledge about the healing properties of plants.
"When I walk around outside, I think of the plants I see as a great, green pharmacy. But what also strikes me is how little we actually know about what that pharmacy has to offer. Studying organisms engaged in self-medication gives us a clue as to what compounds might be worth investigating for their potential as human medicines."
Monarch butterflies are known for their annual migrations to Mexico, where the insect overwinters. The butterflies migrate from Eastern Canada to Mexico each year. One of the more popular butterfly overwintering locations is now a UNESCO World Heritage Site
The brightly coloured orange, black and white butterflies are toxic to their predators, and it is believed the colouring of the Monarch warns a would-be predator of their toxic nature. The butterflies feed on many different varieties of milkweed, which make the butterflies toxic.
de Roode had originally been studying if the Monarchs were choosing more poisonous varieties of milkweed to create better protection from predators, but while undertaking that study,
"... de Roode wondered if the choice could be related to the parasite Ophryocystis elektroscirrha. The parasites invade the gut of the caterpillars and then persist when they become adult monarchs. An infected female passes on the parasites when she lays her eggs. If the adult butterfly leaves the pupal stage with a severe parasitic infection, it begins oozing fluids from its body and dies. Even if the butterflies survive, they do not fly as well or live as long as uninfected ones."
The idea that animals other than humans might use medicinal plants to treat themselves for illness or parasites was an accidental discovery that came about in the 1970s, reported Jerome Burne
in The Guardian in 2002.