Male Flies Find a Mate With Wedding Gifts Made of Vomit and Weird Dancing

Some species of fruit flies vomit and dance to attract a mate and some do not. Why do different species behave differently? Neurobiologists—scientists who study the link between the brain and biology—are always looking for clues. And they've just found a major one: the same gene is involved in the mating rituals of two species of fruit flies, even though they act completely differently toward their mates. 

A species of fruit fly known as Drosophila subobscura engage in a mating dance that includes what the researchers call a “nuptial gift,” which is a nicer way of saying that the male regurgitates so the female can taste the male's vomit to decide whether he's suitable. The neural circuitry responsible for this behavior is linked to a gene called "fru," also known as the fruitless gene. But it turns out that this gene is also linked to the mating behavior of Drosophila melanogaster, which does not perform the vomit-centered ritual.  

The researchers, led by Daisuke Yamamoto, a molecular biologist at Tokyo University, subjected groups of fruit flies to testing in order to see if they could induce the mating circuitry in the flies. “Test males were “unconscious,” yet they regurgitated “the gift” when the right neural circuit was forcibly activated in the absence of a potential partner for mating,” Yamamoto told Newsweek over email. “Thus kissing to get married is based on a hardwired program, that’s amazing.”

Male flies that lack the fruitless gene don’t perform these kinds of courtship behaviors. When researchers artificially activated the fruitless circuitry with light, the flies were compelled to perform their mating rituals, but still in ways that were species-specific. A study of the two species was published today in the journal JNeurosci.

Gene editing enabled the researchers to avoid some pitfalls that past similar research has encountered. “Most researchers currently perform experiments using only established model organisms because of their ease of use, but this makes understanding species-specific behaviors and brain anatomy very difficult,” explained first author Ryoya Tanaka. “Our research begins to address these questions by editing the genome of a non-traditional model species to introduce tools into this organism that allow us to manipulate neuronal activity, comparable to what is available in traditional models. This has then allowed us to compare neural circuits between related model and non-model species to determine how and where species-specific behaviors arise.”

The research might also have some applications for agricultural pest control. Yamamoto explained that if we can inhibit the mating behavior by adding some (human-safe) chemicals to foods on which male flies rely, we could reduce the population in size.

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