As planktonic organisms the larvae of the marine annelid Platynereis swim freely in the open water. They move by activity of their cilia, thousands of tiny hair-like structures forming a band along the larval body and beating coordinately.
Light microscope image of the larva of the marine annelid Platynereis. The larvae swim freely in the sea, moved by activity of their thousands of tiny hair-like structures, which form a band along the larval body (ciliary band), beating coordinately. © Markus Conzelmann, MPI for Developmental Biology
Researchers discovered various neuropeptides in the nerve cells of Platynereis (white). They are highlighted in different colours in this image. © Albina Asadulina and Markus Conzelmann, MPI for Developmental Biology
With changing environmental conditions the larvae swim upward and downward to their appropriate water depth. Scientists of the Max Planck Institute for Developmental Biology in Tübingen, Germany have now identified some signalling substances in the larval nervous system regulating swimming depth of the larvae. These substances influence the ciliary beating and thus hold the larvae in the preferred water depth. The scientists discovered a very simple circuitry of nerve cells underlying this regulation, reflecting an early evolutionary state of the nervous system.
The locomotory system of many animals is muscle based. However, small marine animals often move by cilia. This type of locomotion is more ancient in evolution than muscle-based locomotion and very common in marine plankton. Besides the annelid larvae, the larvae of many marine invertebrates are part of this plankton, for example larvae of snails, sea shells and starfish.
“Not much is known about how the nervous systems of the marine plankton regulate ciliary beating, since the locomotion of intensely explored model organisms like the fruit fly is based on muscles,” says Gáspár Jékely. Together with his team at the Max Planck Institute for Developmental Biology and in cooperation with Thomas A. Münch at the Centre for Integrative Neuroscience in Tübingen, he has examined in detail the nervous system of marine annelid larvae of Platynereis dumerilii.
The ciliary band of Platynereis larvae serves as a swimming motor in the seawater: When cilia beat fast and continuously, larvae swim upward, and when cilia cease beating, the larvae sink. These larvae sense different environmental conditions, e.g. they react to changes in temperature, light and food supply, and alter their movement in the water column accordingly.
In order to gain insight into the regulation of this behaviour, the Tübingen scientists analysed the genes of Platynereis. They discovered several neuronal signalling substances, so-called neuropeptides in their Platynereis gene databases. Moreover, the scientists found that these neuropeptides are produced in single sensory nerve cells of the larva and are released directly at the ciliary band. The scientists concluded that these nerve cells send the sensory information directly on to the cilia. Some of these neuropeptides influence over cilia beating frequency, others act on the frequency of cilia holdups as well. By means of the neuropeptides, the scientists could control the up and down movement of freely swimming larvae and change their swimming depth in the water column deliberately.
“We have discovered that the responsible nervous circuitries are built in an unusually simple way. The sensory nerve cells have motor function at the same time, that is, they send the motion impulse directly to the ciliary band,” says Markus Conzelmann from the Max Planck Institute for Developmental Biology, first author of the study. Such simple circuitries are not known from the regulation of muscle-based locomotion. “We were astonished to find not only one neuropeptide as part of such a simple circuitry, but eleven different ones.”
According to the scientists this discovery gives insights into the form and function of nerve systems in an early stage of evolution. Moreover, the results could be interesting for other fields of marine biology: “We now have a suitable model to further explore the regulation of swimming depth in marine plankton. Since the swimming behaviour of plankton is crucial for the survival and prevalence of thousands of marine animal species, our research results could be relevant for marine ecology,” explains Gáspár Jékely. In his future research he wants to reveal how single nerve cells process the different sensory information from water pressure, temperature or salinity.
The Max Planck Institute for Developmental Biology conducts basic research in the fields of biochemistry, genetics and evolutionary biology. It employs about 325 people and is located at the Max Planck Campus in Tübingen. The Max Planck Institute for Developmental Biology is one of 80 research institutes that the Max Planck Society for the Advancement of Science maintains in Germany.Contact
Dr. Gáspár Jékely | EurekAlert!
Embryonic development: How do limbs develop from cells?
18.05.2018 | Humboldt-Universität zu Berlin
Reading histone modifications, an oncoprotein is modified in return
18.05.2018 | American Society for Biochemistry and Molecular Biology
So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics
Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...
The historic first detection of gravitational waves from colliding black holes far outside our galaxy opened a new window to understanding the universe. A...
A team led by Austrian experimental physicist Rainer Blatt has succeeded in characterizing the quantum entanglement of two spatially separated atoms by observing their light emission. This fundamental demonstration could lead to the development of highly sensitive optical gradiometers for the precise measurement of the gravitational field or the earth's magnetic field.
The age of quantum technology has long been heralded. Decades of research into the quantum world have led to the development of methods that make it possible...
Cardiovascular tissue engineering aims to treat heart disease with prostheses that grow and regenerate. Now, researchers from the University of Zurich, the Technical University Eindhoven and the Charité Berlin have successfully implanted regenerative heart valves, designed with the aid of computer simulations, into sheep for the first time.
Producing living tissue or organs based on human cells is one of the main research fields in regenerative medicine. Tissue engineering, which involves growing...
A team of scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg investigated optically-induced superconductivity in the alkali-doped fulleride K3C60under high external pressures. This study allowed, on one hand, to uniquely assess the nature of the transient state as a superconducting phase. In addition, it unveiled the possibility to induce superconductivity in K3C60 at temperatures far above the -170 degrees Celsius hypothesized previously, and rather all the way to room temperature. The paper by Cantaluppi et al has been published in Nature Physics.
Unlike ordinary metals, superconductors have the unique capability of transporting electrical currents without any loss. Nowadays, their technological...
02.05.2018 | Event News
13.04.2018 | Event News
12.04.2018 | Event News
18.05.2018 | Power and Electrical Engineering
18.05.2018 | Information Technology
18.05.2018 | Information Technology