Tricksy insects sing a song of love and deceit

motheyes

Beyond a spider snacking on an unfortunate fly, the social lives of insects tend to go unrecognized. Perhaps you notice all the ants marching in a line, or bees heading back to a nest, but it all seems so mechanical, so primal.

In reality, insects have social lives that are more complex than you might imagine. One of the most intriguing is insect courtship. Across many species – such as crickets, fruit flies, moths – males must sing to the female in order to mate. The female will listen, considering, and if the male does well enough? Then he can mate. If he can’t sing well enough? He’s out.

While beautiful and touching, it does make you wonder why? Why should a female care that a male can sing well? There is evidence that song can indicate the fitness of the male – males with better song have offspring that are more likely to survive. However, insects often live in mixed environments that consist of many different species. If you dare, go to a garbage heap buzzing with flies. Chances are that it will have big ones and small ones, many different species competing for the same food. One way to screen out the wrong type of fly is to listen for the right song.

But insects are sneaky and can have alternative motives. Another use of the song lies not just in wooing the ladies, but in scaring off competitors. Males of one species of moth will shout out a string of shrieks that sound like the ultrasonic homing call of the bat. Look at the figure below: while the long, crooning song used to attract females doesn’t scare off other males, bat calls – or the short pulse of other males – will send them packing (capture rate is the probability of a moth making its way to a trap emitting courtship pheromones).

scary song

Insects are tricky creatures, able to sneakily imitate predators in order to scare off competitors before deftly turning to romantic ballads.

References

Nakano, R., Ihara, F., Mishiro, K., Toyama, M., & Toda, S. (2014). Double meaning of courtship song in a moth Proceedings of the Royal Society B: Biological Sciences, 281 (1789), 20140840-20140840 DOI: 10.1098/rspb.2014.0840

Hoikkala, A., Aspi, J., & Suvanto, L. (1998). Male courtship song frequency as an indicator of male genetic quality in an insect species, Drosophila montana Proceedings of the Royal Society B: Biological Sciences, 265 (1395), 503-508 DOI: 10.1098/rspb.1998.0323

Photo by Johan J.Ingles-Le Nobel

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Oops! Late as always

I couldn’t get my act together to finish a paper write-up early in the week – holidays and then busy in lab, plus it’s about 4 papers (!) instead of the normal 1 – so enjoy these anecdotes from Information Processing:

WSJ: … When the great California Institute of Technology geneticist Seymour Benzer set out in the mid-1960s to find mutations in fruit flies that affected behavior, rather than mere anatomy, he was ridiculed for challenging the consensus that all behavior must be learned.

Benzer told the geneticist Max Delbrück about the plan to find behavioral mutants; Delbrück said it was impossible. To which Benzer replied: “But, Max, we found the gene, we’ve already done it!” (Benzer’s mother was more succinct: “From this, you can make a living?”) He was soon able to identify mutations related to hyperexcitability, learning, homosexuality and unusual circadian rhythms, like his own: Benzer was almost wholly nocturnal.

Since then, thanks to studies of human twins and a rash of genetic investigations in animals, it has become routinely accepted that most things, including personality, sexual orientation and intelligence, are to some degree affected by genes. The University of Virginia’s Eric Turkheimer has declared what he calls the “first law of behavior genetics”: that all human behavioral traits are heritable.

He’s got a lot of good stuff there, read it all!

 

 

Why you’ll become an alcoholic unless you get more sex

One very social behavior involves a man and a woman who love each other very much (hint: I’m talking about sex).  Flies who love each other very much obviously also mate, although you may not know that they undergo a courtship ritual first – not just any ol’ fly is getting to home plate.  That’s a behavior I’ll talk more about in a future post.  What I want to talk about here is instead what happens to that unlucky guy who, know matter how hard he tries, isn’t getting any.

A recent paper looked at this very question by taking a bunch of flies, and either having one group that either had a lot of sex or were rejected.  And can I say how awesome this sounds?  Listen to the protocol: one group of male flies experienced 1-hour sessions of sexual rejection three times a day for four days.  Another group experienced six-hour sessions of mating with multiple receptive virgin females for four days.  Let’s just say that you probably couldn’t do this kind of science in people.

The flies were then given the choice between food with alcohol and food without alcohol.  When the flies were sexually satisfied, they went without the alcohol; the flies were rejected needed that extra beer.  It turns out even virgin flies choose the alcohol – though they like it less than the rejected flies – which means that it is the lack of sex that mainly influences how much they need to drink.  If these same flies are allowed to mate?  Then they don’t need the alcohol anymore!

Desire, motivation and addiction in the brain are normally associated with the neural chemical dopamine.  But in this paper they looked at a neural peptide instead.  In humans, the neural peptide Y regulates alcohol consumption, as does all kinds of stress like PTSD and early maternal separation.  The equivalent peptide in fly is neural peptide F (NPF).  When they measured the amount of NPF in these flies, they found that it matched the desire for alcohol: the sexually rejected males had the lowest amount of NPF, the virgins had a little more, and the mated males had the most.  By decreasing the amount of NPF with siRNA or artificially activating it, they were able to control how much the flies wanted the alcohol.

So what is happening in the brain in response to sex?  Sex releases this neuropeptide – NPF in flies, NPY in humans – and the peptide is rewarding!  You love it (no surprise there)!  The peptide probably sets in motion changes in the larger reward system, modifying dopamine transmission over the course of many days.  This reveals the importance of investigating how we interact with our environment and fellow creatures in order to understand how our brain really works.

Reference

Shohat-Ophir, Kaun, Azanchi, Huberlein.  Sexual deprivation increases ethanol intake in Drosophila.  Science (335) 1351-1355.  DOI: 10.1126/science.1215932

See also the perspective.