Heliconius melpomene Butterflies Mating

Heliconius melpomene butterflies mating in captivity in Panama. Credit: Kelsey Byers

Butterflies have developed to produce a strongly scented chemical in their genitals that they leave behind after sex to discourage other males from pursuing their females– researchers have discovered.

Researchers discovered that a chemical made in the sex glands of the males of one species of tropical butterfly is identical to a chemical produced by flowers to bring in butterflies.

The study published in PLOS Biology today (January 19, 2021) determined a gene for the very first time that shows butterflies and flowers separately evolved to make the very same chemical for various purposes.

Researchers led by Professor Chris Jiggins, St John’s College, University of Cambridge, mapped production of the aromatic chemical compound to the genome of a types of butterfly, called Heliconius melponene, and discovered a new gene.

Dr. Kathy Darragh, lead author of the paper, said: “We identified the gene accountable for producing this powerful anti-aphrodisiac scent called ocimene in the genital areas of male butterflies. This reveals that the advancement of ocimene production in male butterflies is independent of the advancement of ocimene production in plants.

Kathy Darragh

Dr. Kathy Darragh, very first author of the paper, with a Heliconius butterfly in the Madingley insectary in Cambridge. Credit: Tom Almeroth-Williams

” For a long period of time it was thought bugs took the chemical substances from plants and after that utilized them, however we have actually revealed butterflies can make the chemicals themselves– but with very various intents. Male butterflies utilize it to repulse rivals and flowers use the same odor to attract butterflies for pollination.”

There are around 20,000 types of butterflies worldwide. Some only live for a month but the Heliconius melponene butterflies found in Panama that were studied live for around 6 months. The females typically have few sexual partners and they store the sperm and utilize it to fertilize their eggs over a number of months after a single breeding.

Male butterflies have as many mates ‘as they can’ and each time they transfer the anti-aphrodisiac chemical because they want to be the one to fertilize the offspring. This chemical, nevertheless, is not produced by all Heliconius butterflies.

If the odor has such an effective result, how do the butterflies understand when to be attracted or when to avoid?

Dr. Darragh, now based at the University of California, Davis, discussed: “The visual cues the butterflies get will be essential– when the aroma is spotted in the presence of flowers it will be appealing however when it is discovered on another butterfly it is repulsive to the males– context is key.”

This new analysis of the power of odor– likewise called chemical signaling– sheds new light on the importance of aroma as a form of communication.

Teacher Jiggins said: “The butterflies most likely adjusted to identify it and discover flowers and they have then developed to utilize it in this very different way. The males want to pass their genes onto the next generation and they don’t desire the females to have infants with other daddies so they utilize this fragrance to make them unsexy.

” Male butterflies bother the females a lot so it might benefit the women too if the smell left means they stop being troubled for sex after they have already mated.”

Reference: “A novel terpene synthase manages distinctions in anti-aphrodisiac pheromone production between closely associated Heliconius butterflies” 19 January 2021, PLOS Biology
DOI: 10.1371/ journal.pbio.3001022

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