New research on magnetite in salmon noses illuminates understanding of
sensory mechanisms enabling magnetic perception across life

Date:
January 10, 2022
Source:
Oregon State University
Summary:
Scientists suggest magnetite crystals that form inside specialized
receptor cells of salmon and other animals may have roots in
ancient genetic systems that were developed by bacteria and passed
to animals long ago through evolutionary genetics.



FULL STORY ==========================================================================
It's widely understood that animals such as salmon, butterflies and birds
have an innate magnetic sense, allowing them to use the Earth's magnetic
field for navigation to places such as feeding and breeding grounds.


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But scientists have struggled to determine exactly how the underlying
sensory mechanism for magnetic perception actually works.

In a paper published this week in the Proceedings of the National Academy
of Sciences, an international team of researchers, including scientists
from Oregon State University, outlines a new theory. Magnetite crystals
that form inside specialized receptor cells of salmon and other animals
may have roots in ancient genetic systems that were developed by bacteria
and passed to animals long ago through evolutionary genetics.

The theory is based on new evidence from nanoscopic magnetic material
found within cells in the noses of salmon. The paper's lead author is
Renee Bellinger, who began the research as a doctoral student at Oregon
State, completing her Ph.D. in fisheries science in 2014.

"The cells that contain magnetic material are very scarce," said
Bellinger, who now works as a research geneticist at the U.S. Geological
Survey and is affiliated with the University of Hawaii, Hilo. "We weren't
able to definitively prove magnetite as the underlying key to magnetic perception in animals, but our study revealed associated genes as an
important tool to find new evidence of how potential magnetic sensors
may function." "Finding magnetic receptors is like trying to find a
needle in haystack. This work paves the way to make the 'needle' glow
really bright so we can find and understand receptor cells more easily," Bellinger said.



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The findings have the potential for widespread application, from improving salmon management through better understanding of how they use the ocean
to targeted medical treatments based on magnetism, said coauthor Michael
Banks, a fisheries genomics, conservation and behavior professor at
Oregon State.

"Salmon live a hard and fast life, going out to the ocean to specific
areas to feed and then coming back to their original spawning grounds
where they die.

They don't have the opportunity to teach their offspring where to go,
yet the offspring still somehow know where to go," Banks said. "If we can figure out the way animals such as salmon sense and orient, there's a lot
of potential applications for helping to preserve the species, but also
for human applications such as medicine or other orientation technology." Bellinger's work built on research from more than 20 years ago by Michael Walker of the University of Auckland in New Zealand, who initially traced magnetic sensing to tissue in the noses of trout.

"He narrowed it down to magnetite in the olfactory rosette," Bellinger
said.

"We were expecting to see chains of crystals in the noses of salmon,
similar to how magnetite-producing bacteria grow chains of crystals and
use them as a compass needle. But it turns out the individual crystals
are organized in compact clusters, like little eggs. The configuration
was different than the original hypothesis." The form in which magnetite appears, as tiny crystals inside specialized receptor cells, represents biomineralization, or the process by which living organisms produce
minerals. The similarity between magnetite crystals of bacteria and
fish suggests that they share a common evolutionary genetic history,
Bellinger said.



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The mechanism for developing magnets was developed by bacteria more
than two billion years ago and then passed on to animals. Today, these
tools to perceive magnetism continue to be present across a broad array
of animal species, said Banks, who is affiliated with OSU's Department
of Fisheries, Wildlife, and Conservation Sciences in OSU's College of Agricultural Sciences and the Coastal Oregon Marine Experiment Station
at OSU's Hatfield Marine Science Center.

The process for sharing them across animal life may have been similar to
the evolution of mitochondria, which control how animals release energy.

Mitochondria originated in bacteria and were then transferred to other organisms, he said.

Understanding the evolutionary history of magnetite is a step toward
further pinpointing the underlying process, the researchers said. Banks, Bellinger and colleagues would next like to test their new understanding
and associated markers to further address the mystery of why and how
some life forms have well-tuned tools for long and precise migratory strategies.

Co-authors of the paper are Jiandong Wei of Shanghai University in
China; Uwe Hartmann of Saarland University in Germany; Herve Cadiou
of the Institute of Cellular and Integrative Neuroscience in France;
and Michael Winklhofer of the University of Oldenburg in Germany.

Bellinger's work was supported in part by a Mamie Markham Research Award; several awards of up to $10,000 are available to support research by
graduate students at Hatfield Marine Science Center each year. These
funds allowed Bellinger to travel to France to conduct primary research
for the project.

========================================================================== Story Source: Materials provided by Oregon_State_University. Original
written by Michelle Klampe. Note: Content may be edited for style
and length.


========================================================================== Journal Reference:
1. M. Renee Bellinger, Jiandong Wei, Uwe Hartmann, Herve' Cadiou,
Michael
Winklhofer, Michael A. Banks. Conservation of magnetite
biomineralization genes in all domains of life and implications
for magnetic sensing.

Proceedings of the National Academy of Sciences, 2022; 119 (3):
e2108655119 DOI: 10.1073/pnas.2108655119 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/01/220110184842.htm
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