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 Climate Impact Research in Hannover: Small Plants against Large Waves
17.08.2018 | Leibniz Universität Hannover

nachricht First transcription atlas of all wheat genes expands prospects for research and cultivation
17.08.2018 | Leibniz-Institut für Pflanzengenetik und Kulturpflanzenforschung

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Color effects from transparent 3D-printed nanostructures

New design tool automatically creates nanostructure 3D-print templates for user-given colors
Scientists present work at prestigious SIGGRAPH conference

Most of the objects we see are colored by pigments, but using pigments has disadvantages: such colors can fade, industrial pigments are often toxic, and...

Im Focus: Unraveling the nature of 'whistlers' from space in the lab

A new study sheds light on how ultralow frequency radio waves and plasmas interact

Scientists at the University of California, Los Angeles present new research on a curious cosmic phenomenon known as "whistlers" -- very low frequency packets...

Im Focus: New interactive machine learning tool makes car designs more aerodynamic

Scientists develop first tool to use machine learning methods to compute flow around interactively designable 3D objects. Tool will be presented at this year’s prestigious SIGGRAPH conference.

When engineers or designers want to test the aerodynamic properties of the newly designed shape of a car, airplane, or other object, they would normally model...

Im Focus: Robots as 'pump attendants': TU Graz develops robot-controlled rapid charging system for e-vehicles

Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.

Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....

Im Focus: The “TRiC” to folding actin

Proteins must be folded correctly to fulfill their molecular functions in cells. Molecular assistants called chaperones help proteins exploit their inbuilt folding potential and reach the correct three-dimensional structure. Researchers at the Max Planck Institute of Biochemistry (MPIB) have demonstrated that actin, the most abundant protein in higher developed cells, does not have the inbuilt potential to fold and instead requires special assistance to fold into its active state. The chaperone TRiC uses a previously undescribed mechanism to perform actin folding. The study was recently published in the journal Cell.

Actin is the most abundant protein in highly developed cells and has diverse functions in processes like cell stabilization, cell division and muscle...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

LaserForum 2018 deals with 3D production of components

17.08.2018 | Event News

Within reach of the Universe

08.08.2018 | Event News

A journey through the history of microscopy – new exhibition opens at the MDC

27.07.2018 | Event News

 
Latest News

Smallest transistor worldwide switches current with a single atom in solid electrolyte

17.08.2018 | Physics and Astronomy

Robots as Tools and Partners in Rehabilitation

17.08.2018 | Information Technology

Climate Impact Research in Hannover: Small Plants against Large Waves

17.08.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>