Scientific Method / Science & Exploration

The weird science of high-temperature mating in headless flies

Glowing glands, happy hammocking, threatening dishwashers, and how your spit …

Headless male flies engineered to get horny in the heat: Studying mating behavior, even in an organism as simple as a fruit fly, can be challenging, since it depends on a complex set of interactions between two individuals that may not share the researchers' interest in seeing mating take place. So, some researchers (including one I went to grad school with) decided to take a shortcut. They engineered flies so that male-specific neurons would express a construct that activated the neurons when they were shifted to higher temperatures. It worked, perhaps a bit too well: "Almost all steps of courtship, from courtship song to ejaculation, can be induced at very high levels through [its] activation in solitary males." In other words, heat the male flies up, and they'll just ejaculate, even if they're on their own (although they'll do a mating dance for nobody first). In fact, it even worked if the males' heads were chopped off, driven by the activity in their nerve cord.

About the only thing the males still cared about was what species they were going after, as they courted members of their own species more intensely than any other flies placed in the same vial.

Excuse me, your gland is glowing: And that is a good thing. The thyroid and parathyroid are hormone-producing glands that reside at the base of the neck. They may be physically close and share a similar name, but they do very different things, and problems with one usually doesn't mean that there's anything wrong with the other. Which creates a problem, since removing one while leaving the other intact is a serious challenge for surgeons. Fortunately, a team of surgeons and engineers have found a way to figure out which tissue is which: the parathyroid glows. You need to illuminate it with light just on the infrared side of the visible spectrum, and the glow is also in the near infrared, but the parathyroid is much brighter than any other tissue in the neck if you look at it with the right equipment. That should increase the chances that surgeons can remove one without damaging the other.

A scientific rationale for rocking a baby to sleep: Or, how you can justify getting that hammock you've always wanted. Researchers in Switzerland figured that, since the association of rocking with sleep has persisted across cultures and generations, there was probably something to it, so they put subjects on a slowly rocking bed. Those subjects fell asleep more easily and experienced a longer stretch of a key phase of non-REM sleep. The authors propose that "sensory stimulation associated with a swinging motion exerts a synchronizing action in the brain that reinforces endogenous sleep rhythms."

Cycling through males, steady with lesbians: There are lots of studies out there that indicate women subtly change their sexual behavior in response to their menstrual cycles. According to a study from a group in Canada, one of these changes involves their ability to figure out who is a viable mate. The researchers tracked their ability to identify heterosexual males across the menstrual cycle; accuracy peaked at ovulation. A control situation, identifying lesbians in a group of women, didn't change at all in response to the cycle. The enhanced gaydar was actually a secondary effect of an enhanced interest in sex; simply priming the women with subtle romantic images was sufficient to produce the same effect.

Your dishwasher may be trying to kill you; no word on your other appliances: Researchers have now sampled the microbial communities in 189 dishwashers, located on every continent except Antarctica. Half of them contained species of fungi that cause respiratory problems in humans. The authors suggest that there's some overlap between the humid dishwasher environment and the sorts of places human pathogens prefer, which creates a bit of a health risk.

Your spit makes you look old: How's this for a depressing start to a paper: "From the moment of conception, we begin to age." Still, it's worth lifting yourself out of the pits of despair to read beyond that, because the results are a bit surprising. We've known that many areas of DNA pick up a chemical modification called methylation as organisms develop. But the researchers tested 34 pairs of identical twins, and discovered that there are areas of the genome where methylation increases with age, including three sites where it shows a linear increase for spans of over 50 years. Testing as few as two individual sites was sufficient to predict age with an average accuracy of 5.2 years.

The authors point out that there's usually sufficient DNA in environmental samples to do these sorts of tests, which could prove very useful for police, who could add age to the profile they build from forensic evidence.

Listing image by Photo illustration by Aurich Lawson based on a photograph by Gustavo Durán

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