Beauty doesn’t only fade within a lifetime–it also fades genetically over the course of several generations, according to new research. Scientists studying populations of sexually attractive male fruit flies have found that there’s a limit to their evolutionary success–and that there may actually be a disadvantage to being too sexy.
For the study, published in the Proceedings of the National Academy of Sciences, researchers genetically modified male fruit flies, causing them to give off excessive amounts of attractive pheromones. The scientists then introduced a flock of these foxy fellows to a normal fruit fly population. They discovered that the female flies mated with these modified flies more often initially, and the proportion of super-sexy males increased for a while–but the proportions returned to normal after seven generations.
As The New York Times reports:
“Even though we were able to make males more attractive, there must have been a fitness cost,” said Katrina McGuigan, a biologist at the University of Queensland and one of the study’s authors. “While sexual selection is really powerful, there are consequences to nonsexual traits.”
It’s not yet clear what genetic disadvantage these fruit fly ladykillers may have had. But let’s turn to the more urgent question: Is there any carryover implications for humans? The New York Times quotes McGuigan:
“Hard to say, but only that very attractive individuals may well have something wrong with them — they may not be as good as they seem to be at first glance.”
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Image: Wikimedia Commons / A. O’Toole
The humble fruit fly is overturning the science of smell. Using the fruit fly’s sensitive schnoz, scientists now have evidence that the sense of smell isn’t only a matter of molecular shape–it might also have something to do with how the molecules entering the nose vibrate.
Previously, scientists thought that we perceive a particular smell when an olfactory molecule’s shape matches the shape of receptors in our nose. The molecule enters the receptor, and so we perceive the particular smell triggered by that lock-and-key scenario. But in 1996, MIT Biophysicist Luca Turin suggested that the patterns in which molecules vibrate are what control odor.
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Microscopy often yields striking snapshots, but these colorful compositions have a less-than-glamorous subject: fruit fly intestines.
The insides of these humble critters may help researchers understand the human digestive system. Each of us has something like 500 million intestinal nerve cells, yet little is known about what they’re up to. According to a recent Wellcome Trust press release, fruit fly feces (seen in image 3 above) have helped researchers at the University of Cambridge understand how the gut’s nerve cells affect metabolism.
“We reasoned that what comes out of the gut may be able to tell us about what is going on inside,” says Irene Miguel-Aliaga, who headed the study. “So, we devised a method to extract information about several metabolic features from the flies’ fecal deposits–which are actually rather pretty and don’t smell bad. Then we turned specific neurons on and off and examined what came out.”
Examining fruit fly poo allowed the scientists to assign different functions to different intestinal neurons. Some regulate appetite, for example, while others adjust intestinal water balance during reproduction.
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Do I smell a banana? Nope. It’s a blue light I’m smelling.
Fruit fly larvae made this mistake while participating in a study recently published in Frontiers in Neuroscience Behavior. By adding a light-sensitive protein to certain smell receptors in the larvae, German scientists allowed the genetically engineered bugs to essentially smell light.
The team, under the guidance of Klemens Störtkuhl at Ruhr University Bochum, is attempting to understand “olfactory coding”–how the brain transforms chemical signals into perceptible smells. Normally, a fly’s olfactory receptor neurons only send an electrical signal to its brain when the fly smells something, but by adding a protein the researchers caused a neuron to fire when the one-millimeter bug was basking in blue light.
The fly brain uses some of its 28 olfactory neurons to detect bad smells, and others for good ones. Protein puppeteers, the researchers could pick which neuron to add the light-sensing protein to. The good-smelling neurons respond to a smorgasbord of fly-friendly scents: like banana, marzipan, and glue (apparently rotting fruit gives off these scents). By attaching the light-sensitive protein to one of these neurons, researchers caused the typically light-fearing insects to crawl straight towards the blue glow.
According to a ScienceDaily article, given their successful mapping of these larvae olfactory neurons, the researchers next hope to make adult fruit flies go bananas.
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Image: flickr / Jason Gulledge
When it comes to peculiar penises, there’s no shortage in the animal kingdom. Just last month DISCOVER blogger Carl Zimmer documented new research into why many male ducks have such an extravagant spiral-shaped phallus. This week, in a paper (in press) in the Proceedings of the Royal Society B, the study of goofy genitalia follows fruit flies.
The male fruit fly has a penis that resembles a medieval weapon, dotted with hooks and spines. Are those barbs there to remove rival sperm, or pierce the female’s genital tract to allow sperm a shortcut, or something else? There was one way to find out: lasers.
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Not all animals have fun during the mating process. Seed beetles can get pretty beaten up, and fruit flies can even get sick from it.
When female fruit flies mate, their immune system responds to the sperm the same way it does to germs. University of California, Santa Barbara evolutionary biologist Andrew Stewart sees the immune system as a battleground, a place where the sexes can compete—a female’s immune system will rev up so it can fight off the proteins in the ejaculate, so she can live longer and have more babies.
But the exact reason for this immune response is still up in the air. It’s possible the male knows that the female has mated with other male flies, and uses the pathogens in his sperm to beat the other males in fertilizing eggs. Regardless, females still pay a heavy price: Most females mate with several partners, even though if they mate just once, their life span is shortened significantly.
But the beetles have it worse, because their mating is so brutal: When a female decides to mate, she repeatedly gets jabbed by the male’s sexual organ, which looks more like a medieval weapon than pleasure tool. But the females put up with the roughness, apparently because they are so thirsty.
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