Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Casanova or caveman: Scientists isolate nerve cells that choreograph male fly’s courtship behavior

29.07.2004


When a male fruit fly encounters a prospective mate, he initiates courtship by following her around and gently tapping her with his leg. If she seems interested, he serenades her with a love song. Singing is followed by more intimate acts that sometimes lead to successful mating.

Now Stanford University scientists have discovered that this elaborate courtship behavior is actually choreographed by a cluster of nerve cells embedded in the central nervous system of the male fly. When these cells fail to function properly, the courtship ritual breaks down and the male is transformed from a suave Casanova into a clumsy brute that tries to force himself on unwilling females.

These findings, published in the July 29 edition of the journal Nature, may eventually help scientists understand how the brain orchestrates sexual behavior in a variety of species - from flies to reptiles to humans, according to the researchers.



"The fruit fly is a model organism whose basic cellular functions are very similar to what they are in people," said Bruce S. Baker, the Dr. Morris Herzstein Professor in Biology at Stanford and co-author of the Nature study. "It wouldn’t surprise me to learn that human sexual behaviors also have underneath them a basic circuitry in the nervous system that mediates attraction and mating."

Casanova to caveman

In the Nature study, Baker and Stanford graduate student Devanand S. Manoli focused on a gene known as fruitless - one of approximately 13,000 genes in the DNA of the common fruit fly, Drosophila melanogaster.

Baker and several colleagues had previously discovered that fruitless was the master gene that controlled sexual behavior in male flies. "We found that the fruitless gene was responsible for building the neuronal circuitry for male courtship," Baker said. "This circuit, which is built into the fly’s brain and ventral nerve cord, is comprised of about 1,500 neurons - roughly one percent of the total number of nerve cells in a fruit fly."

In the Nature paper, Manoli and Baker showed that 60 of those cells carried out the crucial task of coordinating the steps of the courtship ritual. When those cells didn’t function properly, the male was unlikely to successfully mate, the researchers found.

"Drosophila male courtship is a complex, innate sequence of stereotyped behaviors that are programmed into the male during development," Baker explained. "The fly isn’t taught anything. In fact, he’s ready to mate 24 hours after he emerges from the pupa."

The courtship ritual consists of six steps carried out in a specific order. First, the male senses the presence of the female and follows her. Then he taps the female with his foreleg, which triggers pheromone cues. The male then extends a wing and vibrates it, producing a species-specific courtship song. The fourth step involves licking the female’s genitalia with his proboscis, followed by attempted copulation (step five) and copulation (step six).

"A normal male completes the first three steps in about two minutes," Baker said. "That’s followed by about two minutes of licking before he first attempts copulation." Copulation itself lasts another 20 minutes.

"But when we interfere with the functioning of those 60 nerve cells, the male essentially skips the tapping step and attempts to do everything else at once: He tries to copulate, lick her genitalia and play her a love song simultaneously. So what normally takes a total of four minutes is reduced to just 10 seconds - and that doesn’t work very well."

Reproductive failure

While some mating did occur during the experiment, the mutant males failed to achieve their ultimate goal - reproductive success.

"The mutants did copulate, but it never resulted in fertilization, because they would consistently mis-transfer their sperm and other seminal contents," Baker said. "It also took them longer to achieve copulation than normal males. That may well be because, for successful copulation, it’s female willingness that drives the whole thing. We can well assume that, when the mutant males behave in this way, they are doing things that the female does not find attractive."

Removing the network of nerve cells had other deleterious consequences, Baker noted.

"In normal courtship, to anthropomorphize it, the flies are polite," he said. "Normal males show what we refer to as ’deference’ - once one male starts courting a female, the other male leaves the couple alone for at least a while, postponing his own courtship. But what happens when we put several mutant males together with a female? All the males go after her at the same time."

As an example, Baker pointed to a videotape shot during the experiment in which a female fly is frantically pursued by a half-dozen out-of-control mutants.

"Our study shows that there is an identifiable set of cells, a place in the central nervous system, that serves to coordinate each of the subroutines that make up a behavior - licking, tapping and so forth," Baker said.

"There’s been some debate about whether the courtship ritual is really made up of subroutines or whether it’s one continuum," he added. "What we found is that while interfering with the neural network changes the sequence, the individual subroutines - such as licking and singing - are still there. This suggests very strongly that these subroutines are somehow built into the nervous system itself."

The evolution of courtship

"Another interesting suggestion from our work is that, while rapid mating and multiple male courtship are very abnormal for Drosophila, such behaviors are the norm in other insect species," Baker observed. "This raises the possibility that there is an ancestral neuronal circuit for courtship that’s common to many species, and that the very different courtship behaviors we see throughout the animal kingdom may have come about by relatively minor changes in this circuit."

Although a fruit fly is only a fraction of the size of a human being, Baker noted that both species are strikingly similar in their genetic makeup.

"The list is endless of the ways that people and flies are fundamentally similar," he explained. "For example, most major developmental genes that build the body plan and various organ systems are the same in people and flies."

Could the genes that control sexuality in flies also play a role in directing human sexuality?

"If you look at the basics of fly behavior, you find an innate ability to recognize somebody who is the right species and is the right sex," Baker said. "You tap them and get their attention, you play them a love song and so on. So the basic rudiments are pretty similar to what people do to get successful mating and produce an offspring.

"Of course, the actual way that’s manifested in humans - whether you go to a rock concert or to the opera - is entirely cultural and based on your upbringing. But a basic drive to reproduce and a basic reproductive strategy may be there. The tough job for geneticists is figuring out the pieces of the machinery that actually bring these behaviors about."

Mark Shwartz | EurekAlert!
Further information:
http://www.stanford.edu

More articles from Life Sciences:

nachricht Symbiotic bacteria: from hitchhiker to beetle bodyguard
28.04.2017 | Johannes Gutenberg-Universität Mainz

nachricht Nose2Brain – Better Therapy for Multiple Sclerosis
28.04.2017 | Fraunhofer-Institut für Grenzflächen- und Bioverfahrenstechnik IGB

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Fighting drug resistant tuberculosis – InfectoGnostics meets MYCO-NET² partners in Peru

28.04.2017 | Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

 
Latest News

Wireless power can drive tiny electronic devices in the GI tract

28.04.2017 | Medical Engineering

Ice cave in Transylvania yields window into region's past

28.04.2017 | Earth Sciences

Nose2Brain – Better Therapy for Multiple Sclerosis

28.04.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>