A single protein makes lovesick flies spill their guts

Vomiting up a droplet of sugar won’t appear to be essentially the most romantic gesture from a possible suitor. But for one fly species, males that spill their guts are fairly a catch.

Drosophila subobscura flies’ peculiar “romantic” barfing might need advanced by repurposing brain cells that usually control digestion for more romantic pursuits, researchers report August 14 in Science.

Most male fruit flies court docket by following the females round and vibrating their wings to serenade them with a species-specific love tune, says Adriane Otopalik. But some fly species, like D. subobscura, spice issues up somewhat. The males will vomit a little bit of their final meal and supply it to females they’re concerned with, says Otopalik, a neuroscientist at Howard Hughes Medical Institute’s Janelia Research Campus in Ashburn, Va.

Nuptial presents like these are frequent in some animals, like male spiders trying to win over their mates with out getting their heads bitten off. Scientists suppose feminine flies, which might be “very choosy,” would possibly use this romantic barf to choose appropriate suitors, says Otopalik, who was not concerned within the examine.

The hundreds of neurons that management most of male fruit flies’ courtship produce a male-specific model of a protein known as fruitless. Artificially activating these neurons could make D. subobscura males go through the motions of their seduction dance — even when there aren’t any females round, says Daisuke Yamamoto, an evolutionary biologist at National Institute of Information and Communications Technology in Kobe, Japan.

Yamamoto and his collaborators puzzled if someplace in these courtship mind cells was the important thing to understanding how nuptial reward giving advanced.

The crew discovered {that a} group of 16 to 18 digestion-controlling neurons within the D. subobscura mind had the male model of the fruitless protein. Activating simply that small variety of mind cells triggered males to spill their guts, making them extra profitable at mating with the women of their species.

These similar digestion-related neurons in Drosophila melanogaster don’t produce the male-specific fruitless protein. This fly species diverged from D. subobscura about 30 million to 35 million years in the past and doesn’t have this vomit-wooing technique.

D. melanogaster’s digestion neurons aren’t related to the remainder of the courtship neurons. But when the researchers made these mind cells in D. melanogaster produce the male-specific fruitless protein, male flies vomited as they pursued the females. This additionally made these cells bigger, rising towards and presumably connecting to the courtship neurons on this species. 

This is an “amazing example of … cross-species comparison as a way of trying to understand sort of general principles of how a sex-specific behavior comes into being,” Otopalik says.

In D. melanogaster, the digestion neurons are concerned in effervescent, a conduct the place overstuffed flies vomit a few of their abdomen contents, Yamamoto says.

“These [digestion] neurons actually directly control the motor system,” projecting into the flies’ intestine and mouthparts, Yamamoto says. So nuptial reward giving in all probability advanced by borrowing a whole preexisting vomit circuit and repurposing it into the courtship system.

The mind cells in all probability acquired related accidentally, he says. But the connection was fruitful, and barfing grew to become fairly the romantic gesture.