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 Not of Divided Mind
19.01.2017 | Hertie-Institut für klinische Hirnforschung (HIH)

nachricht CRISPR meets single-cell sequencing in new screening method
19.01.2017 | CeMM Forschungszentrum für Molekulare Medizin der Österreichischen Akademie der Wissenschaften

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

New Study Will Help Find the Best Locations for Thermal Power Stations in Iceland

19.01.2017 | Earth Sciences

Not of Divided Mind

19.01.2017 | Life Sciences

Molecule flash mob

19.01.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>