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 Multi-institutional collaboration uncovers how molecular machines assemble
02.12.2016 | Salk Institute

nachricht Fertilized egg cells trigger and monitor loss of sperm’s epigenetic memory
02.12.2016 | IMBA - Institut für Molekulare Biotechnologie der Österreichischen Akademie der Wissenschaften GmbH

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

Im Focus: Molecules change shape when wet

Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water

In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...

Im Focus: Fraunhofer ISE Develops Highly Compact, High Frequency DC/DC Converter for Aviation

The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.

Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

UTSA study describes new minimally invasive device to treat cancer and other illnesses

02.12.2016 | Medical Engineering

Plasma-zapping process could yield trans fat-free soybean oil product

02.12.2016 | Agricultural and Forestry Science

What do Netflix, Google and planetary systems have in common?

02.12.2016 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>