Magnetoreception Allows Fish to Navigate in the Dark

The scientists focused their work on zebrafish, and distally related medaka fish because they are vertebrate animals that can be genetically addressed and analyzed well under the microscope.* The researchers found that adult fish of both species change their swimming trajectories in response to a change in the direction of the Earth magnetic field that was experimentally introduced while carefully controlling for confounding variables. Interestingly, this effect also occurred in the absence of visible light such that a photon-independent mechanism has to be assumed.

“In this model, we can now look for previously unidentified magnetoreceptor cells, which our behavioral experiments predicted would involve magnetic material”, said co-first author Ahne Myklatun, a graduate student in the Westmeyer laboratory.

In addition, the researchers were able to show a similar magnetic field-dependent effect in young fish larvae. “This is a decisive advantage because in their early developmental stages, the fish are still almost transparent”, said Antonella Lauri, a postdoctoral fellow and joint lead author. “Thus, we can use imaging techniques to study the brain of the fish during behavioral runs with changing magnetic fields.” The scientists were already able to identify a candidate region in the brain – a track that could now lead to the unknown magnetic receptor cells.

Gil Gregor Westmeyer, principal investigator on this ERC-funded study, concludes: “Magnetoreception is one of the few senses whose mechanism is not understood. The kind of multidisciplinary work we present here will ultimately lead to an understanding of the biophysical mechanism of magnetoreception and its underlying neuronal computation. These findings could also offer interesting approaches to engineer biological systems for the remote control of molecular processes with magnetic fields.”

Further Information

* Recently, Westmeyer and his team have successfully developed a new microscope. The so-called NeuBtracker (NeuBtracker.org) is an open source microscope that allows observing neuronal activities in zebrafish without perturbing their behavior.

Background:
In the long term, the team would like to use the findings to develop novel techniques involving magnetogenetics, an innovative research program that could probably also play a role in the new Helmholtz Pioneer Campus (HPC). Here, researchers from various disciplines want to work together on new solutions to medical needs. “For example, in the diabetes context, it would be conceivable to develop cells that are induced by a magnetic impulse to produce insulin,” says Westmeyer.

Prof. Dr. Gil Gregor Westmeyer is affiliated with the Institutes for Biological and Medical Imaging (IBMI) and Developmental Genetics (IDG) at Helmholtz Zentrum München. He is professor of molecular imaging at the Nuclear Medicine Department and a member of the Munich School of Bioengineering (MSB) of the Technical University of Munich (TUM). The study was conducted in close cooperation with scientists at the University of Oldenburg, the University of Hohenheim and the Ludwig Maximilian University of Munich (LMU).

Contacts and sources:
Helmholtz Zentrum Muenchen – German Research Centre for Environmental Health

Myklatun, A. & Lauri, A. et al. (2018): Zebrafish and medaka offer insights into the neurobehavioral correlates of vertebrate magnetoreception. Nature Communications, DOI: 10.1038/s41467-018-03090-6