Education

Trout giving Duke, UNC team clues to sea-creature navigation

Duke biology post-doc Bob Fitak and four of his colleagues collaborated on a study that found 181 genes in rainbow trout brains that react to changes in the magnetic field around the fish. The finding may offer a clue about how the fish navigate.
Duke biology post-doc Bob Fitak and four of his colleagues collaborated on a study that found 181 genes in rainbow trout brains that react to changes in the magnetic field around the fish. The finding may offer a clue about how the fish navigate. Ray Gronberg

Five-inch rainbow trout don’t often figure in fish stories, but at Duke University, 20 of them may have pointed the way to a better understanding of how aquatic creatures navigate.

A team working out of biology professor Sönke Johnsen’s lab reported recently that it’d identified 181 trout-brain genes that reacted when the researchers pulsed the animals with a faint magnetic field.

What that means remains a puzzle, though post-doc Bob Fitak and others on the team hope it eventually contributes to an understanding of how fish, turtles and other sea creatures are able to sense the Earth’s magnetism and use it to find their way.

In their paper, they noted that some of the genes are linked to a protein that stores iron oxide molecules, and that others contribute to the development of the trout’s vision systems.

That fits both of the working theories biologists have for how the magnetic sense in aquatic creatures might work, Fitak said, adding that a genetics-focused approach to the problem offers the chance that researchers “might be able to find the pathways” to how the sense develops.

At Duke, the project’s continuing with a look at genes specifically from rainbow trout retinas, Fitak said. The recent paper looked at samples drawn from the brain.

Collaborative effort

As is the norm in academia these days, and especially so in the Triangle, the work behind this month’s paper took contributions from people at several universities.

From Duke, Johnsen supplied the lab and funding, Fitak the genomics analysis and lab tech Jay Wheeler the care of the animals plus figuring out “what was feasible” in the way of studying them, Fitak said.

From UNC-Chapel Hill, biology professor Ken Lohmann and Ph.D. student David Ernst loaned the “pulse magnetizer” used to created the magnetic field around the 10 fish that received the treatment, and trained their Duke colleagues in its use.

Most of the team received credit in the paper for helping design the study, and all of them helped write up the results.

Obtaining the data took help from the Genomic Sciences Laboratory at N.C. State University, a so-called “core” lab with that has a battery of commercial, off-the-shelf, high-end DNA sequencers.

Duke and UNC have sequencers like them too, but at all three universities, researchers tend to shop around, looking to send their samples to a lab with not just the most up-to-date machinery and software but a queue of work requests that fits their schedule, Fitak said.

The fish themselves came from a private-sector trout farm in Brevard. The team purchased 251 juveniles, one of its members driving from the Triangle to the mountain community to pick them up because the order was too small to qualify for the farm’s we-deliver promise.

Once in Durham, the fish lived in a round, 4-foot-round tank in the basement of Duke’s Biological Sciences Building. When the time came, researchers randomly netted 20 of them for the study, half for a control group that didn’t get the magnetic pulse.

Johnsen, a Swarthmore- and UNC-trained researcher who’s been on Duke’s faculty since 2001, hired Fitak as a post-doc to help build up his lab’s expertise in genomics. Fitak in turn had to get up to speed on sensory biology, Johnsen’s specialty.

A project like the trout study likely would’ve taken “more people and money and time than you could imagine” without the advances in analytics and DNA sequencing that’ve unfolded in the past decade or so, said Fitak, who trained at Ohio State and the University of Arizona.

The grants Johnsen drew on for the project came from the U.S. Air Force, which like the rest of the federal Department of Defense subsidies basic research in biology, particularly into sensory systems.

The Air Force has an obvious motive for trying to push navigation science and technology. When it comes to understanding “magnetoreception” in animals, “they’re not particularly interested in the species,” but in backing research teams that “can get at this mechanism,” Fitak said.

Ray Gronberg: 919-419-6648, @rcgronberg

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