Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

The neurobiological consequence of predating or grazing

18.01.2013
Scientists from Tübingen compare neuronal network connections in two worm species

Researchers in the group of Ralf Sommer at the Max Planck Institute for Developmental Biology in Tuebingen, Germany, have for the first time been able to identify neuronal correlates of behaviour by comparing maps of synaptic connectivity, or “connectomes”, between two species with different behaviour.

They compared the pharyngeal nervous systems of two nematodes, the bacterial feeding Caenorhabditis elegans and the predator/omnivore Pristionchus pacificus and found large differences in how the neurons are “wired” together.

A long standing question in neurobiology is how certain behaviours are reflected in the pattern of connections between neurons. Answering this question requires a comparative approach, which has proved impossible even in a rather small organism like the nematode due to technical limitations in the preparation and analysis of the extremely large data sets. Dan Bumbarger and his colleagues have chosen the pharyngeal nervous systems of C. elegans and P. pacificus, which consist of only 20 neurons and show a high degree of independence from the body nervous system. These 20 neurons regulate the contraction of the pharynx muscles which are responsible for the uptake of food and its processing prior to digestion in the intestine.

Bumbarger has prepared ultra-thin sections of two Pristionchus worms and compared the number and location of synapses in the pharynx nervous system with the existing C. elegans data. Despite the small size of a nematode, data generation and analysis took over three years: Each of the 150 micrometre long pharynx regions yielded more than 3000 sections that had to be individually imaged and analysed under the electron microscope.

The first result of this extensive study came as a surprise: “By means of their shape and position each of the 20 neurons in Pristionchus pacificus could be correlated to an exact equivalent in Caenorhabditis elegans” explains the scientist. “This is all the more astonishing as the evolutionary distance between the two worm species is over 200 million years and they differ markedly in feeding behaviour and in the anatomy of their mouth parts.” While C. elegans feeds exclusively on bacteria, P. pacificus is able to switch its behaviour to prey on other worms if bacterial food gets scarce.

These differences are reflected in the number and position of neuronal synapses. While in C. elegans only 9 out of 20 nerve cells are motor neurons, which primarily activate muscle cells, the number is up to 19 in P. pacificus; only one neuron functions exclusively as an interneuron, establishing connections between nerve cells. “This hints at substantial differences in information flow”, states Ralf Sommer. Clearly, the regulation of movements is much more complex in P. pacificus – a finding which correlates perfectly with the predatory feeding behaviour of the worm.

By means of partly newly developed analytical methods the scientists in Tuebingen also compared the relevance of individual neurons and synapses for the entire network. It became obvious that two neurons in the anterior part of the P. pacificus pharynx have significantly gained in importance: They are the motor neurons regulating the muscle cells that control the movement of mouth parts, most prominently the movement of teeth which are not found in C. elegans. “The mouth parts are particularly active during a predatory attack, but not when feeding on bacteria” explains Sommer. In C. elegans, these two neurons function exclusively as interneurons. There are marked differences in the posterior part of the pharynx as well. This is where C. elegans has a specialized muscular “grinder” for crushing bacteria, their only food source. In P. Pacificus, which does not have a grinder, some of the muscle cells have lost synaptic connections with neurons.

“The patterns of synaptic connections perfectly mirror the fundamental differences in the feeding behaviours of P. pacificus and C. elegans”, Ralf Sommer concludes. A clear-cut result like that was not what he had necessarily expected. Previous studies in much simpler neural circuits - as in the marine snail Aplysia – had indicated that changes in behaviour do not have to coincide with changes in number and location of synapses. Differences in physiological properties of neurons or in their modulation by neurotransmitters can be sufficient to effect behavioural changes.

Original Publication:
Daniel J. Bumbarger, Metta Riebesell, Christian Rödelsperger, Ralf J. Sommer. System-Wide Rewiring Underlies Behavioral Differences in Predatory and Bacterial Feeding Nematodes. Cell (2013), 17 January 2013; doi: 10.1016/j.cell.2012.12.013

Contact:
Ralf J. Sommer
Phone: +49 7071 601- 371
E-mail: ralf.sommer(at)tuebingen.mpg.de

Dan Bumbarger
Phone: +49 7071 601- 440
E-mail: daniel.bumbarger(at)tuebingen.mpg.de

Janna Eberhardt | Max-Planck-Institut
Further information:
http://www.tuebingen.mpg.de

More articles from Life Sciences:

nachricht A new potential biomarker for cancer imaging
05.02.2016 | Universiti Putra Malaysia (UPM)

nachricht NIH researchers identify striking genomic signature shared by 5 types of cancer
05.02.2016 | NIH/National Human Genome Research Institute

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Automated driving: Steering without limits

OmniSteer project to increase automobiles’ urban maneuverability begins with a € 3.4 million budget

Automobiles increase the mobility of their users. However, their maneuverability is pushed to the limit by cramped inner city conditions. Those who need to...

Im Focus: Microscopy: Nine at one blow

Advance in biomedical imaging: The University of Würzburg's Biocenter has enhanced fluorescence microscopy to label and visualise up to nine different cell structures simultaneously.

Fluorescence microscopy allows researchers to visualise biomolecules in cells. They label the molecules using fluorescent probes, excite them with light and...

Im Focus: NASA's ICESat-2 equipped with unique 3-D manufactured part

NASA's follow-on to the successful ICESat mission will employ a never-before-flown technique for determining the topography of ice sheets and the thickness of sea ice, but that won't be the only first for this mission.

Slated for launch in 2018, NASA's Ice, Cloud and land Elevation Satellite-2 (ICESat-2) also will carry a 3-D printed part made of polyetherketoneketone (PEKK),...

Im Focus: Sinking islands: Does the rise of sea level endanger the Takuu Atoll in the Pacific?

In the last decades, sea level has been rising continuously – about 3.3 mm per year. For reef islands such as the Maldives or the Marshall Islands a sinister picture is being painted evoking the demise of the island states and their cultures. Are the effects of sea-level rise already noticeable on reef islands? Scientists from the ZMT have now answered this question for the Takuu Atoll, a group of Pacific islands, located northeast of Papua New Guinea.

In the last decades, sea level has been rising continuously – about 3.3 mm per year. For reef islands such as the Maldives or the Marshall Islands a sinister...

Im Focus: Energy-saving minicomputers for the ‘Internet of Things’

The ‘Internet of Things’ is growing rapidly. Mobile phones, washing machines and the milk bottle in the fridge: the idea is that minicomputers connected to these will be able to process information, receive and send data. This requires electrical power. Transistors that are capable of switching information with a single electron use far less power than field effect transistors that are commonly used in computers. However, these innovative electronic switches do not yet work at room temperature. Scientists working on the new EU research project ‘Ions4Set’ intend to change this. The program will be launched on February 1. It is coordinated by the Helmholtz-Zentrum Dresden-Rossendorf (HZDR).

“Billions of tiny computers will in future communicate with each other via the Internet or locally. Yet power consumption currently remains a great obstacle”,...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

AKL’16: Experience Laser Technology Live in Europe´s Largest Laser Application Center!

02.02.2016 | Event News

From intelligent knee braces to anti-theft backpacks

26.01.2016 | Event News

DATE 2016 Highlighting Automotive and Secure Systems

26.01.2016 | Event News

 
Latest News

A new potential biomarker for cancer imaging

05.02.2016 | Life Sciences

Graphene is strong, but is it tough?

05.02.2016 | Materials Sciences

Tiniest Particles Shrink Before Exploding When Hit With SLAC's X-ray Laser

05.02.2016 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>