Mating, tattoos and leaving home: the story of a growing guppy | MSU Today

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Nature is full of great questions that are easy to ask and hard to answer. With good old-fashioned hard work and the help of a humble gill vertebrate, Michigan State University’s Sarah Fitzpatrick and Isabela Lima Borges made progress on one of these mysteries.

Assistant Professor MSU Sarah Fitzpatrick

The Spartans conducted an extensive study of Trinidadian guppies to gather elusive data on relatively short swims. This information can help explain the greater mystery of why some people leave the safety of home to pursue their lives elsewhere.

“Traveling can be dangerous and it takes energy. Considering all the risks, why are things moving at all? Said Fitzpatrick, assistant professor of integrative biology in the College of Natural Sciences based at WK Kellogg Biological Station, or KBS. “It is such a fundamental element of ecology that we know so little. “

The answers to this question were largely based on theory, but thanks to a new study published in the journal Ecology letters on November 25, the team provided hard data to back it up.

MSU graduate student researcher Isabela Lima Borges

MSU graduate student researcher Isabela Lima Borges

The data is also valuable from a conservation standpoint, said Borges, the first author of the new study and a graduate student researcher in the Department of Integrative Biology, also at KBS. By revealing more of an animal’s natural behavior, researchers can better spot when human activity begins to alter it.

The team showed that although most guppies stayed put throughout their lives, venturing males were more likely to have offspring than their home-stay counterparts. Women tended to move less and saw no benefit in moving more. Still, there was a clear reward for the men who swam in the hen house.

“We get the chicken and the egg,” Borges said. “We see that the males move more and that the males benefit more.”

It wasn’t a total surprise. The theory suggests that because staying at home is often safer – for example, there is less risk of being eaten – there must be some benefit to traveling. Otherwise, why go? But data to confirm the benefits were scarce.

“What we’ve done is take it a step further and track the benefits for the guppies that have left the house,” said Fitzpatrick, who is also a senior faculty member at MSU. Ecology, Evolution and Biology Program and the KBS coordinator Molecular Ecology and Genomics Laboratory. “It’s cool to see a result that makes sense.”

Female guppies, like the fish on the left, saw no reproductive benefit from leaving the house.  In contrast, males, like the fish on the right, who moved more had more offspring.  Credit: Courtesy of Fitzpatrick Lab

Female guppies, like the fish on the left, saw no reproductive benefit from leaving the house. In contrast, males, like the fish on the right, who moved more had more offspring. Credit: Emily Kane

While the unpretentious guppy’s reproductive exploits may not seem like big news, they may indicate how other species are responding to the should-I-stay-or-should-I-go question.

“Although this is a single species study, there are many larger theories that can be drawn from it,” Borges said. “For example, we would expect to see this behavior in other species that do not have male parental care.”

These broader implications are made possible by the special place of the Trinidadian guppy in science. Fish live in streams across Trinidad and each stream presents the guppies that live there with slightly different conditions. So the different streams are almost like different iterations of the same natural experiment, Borges said.

For this reason, scientists have studied fish for decades and established the guppy as a model organism. With a wealth of history and knowledge at their disposal, scientists can use what they learn about guppies to inform their understanding of larger patterns in the natural world.

It sounds like how scientists have long relied on fruit flies to test ideas about genetics and evolution in the lab, Fitzpatrick said, with a few notable differences. Guppies have a backbone, and scientists can study them in the wild with relative ease.

“I tell people that guppies are the fruit fly of the vertebrate world,” said Fitzpatrick, “With them we can study evolution in action in natural environments.”

Four mesh butterfly nets rest in a stream with clear water and a rocky bed.

The team used butterfly nets to extract Trinidadian guppies from their native streams. Credit: Courtesy of Fitzpatrick Lab

However, the study was still intensive. “It was very difficult and it’s an ‘easy’ species to study,” Borges said, which helps explain, in part, why such solid data had not been available before.

In collaboration with collaborators from Colorado State University and the University of Texas at Austin, the researchers “tattooed” around 1,300 guppies. The researchers essentially color-coded individual fish with small, injectable tags to track the movements of the guppies.

The team then fished the guppies out of their streams once a month for a year, noting their position, taking photographs and recording other measurements before releasing the fish to the water.

The data showed that most of the fish stayed in the same pools they were born in, but others ventured tens of meters away (moving more than 10 meters or around 33 feet was considered far away for one. guppy). The record holder swam about 250 meters, or just over 800 feet.


The male Trinidadian guppy is a colorful fish, even without a tattoo. Credit: Emily Kane

Beyond documenting the reproductive benefits of the move, the team also noted other trends in their data. For example, larger males were more likely to move farther than smaller males. And fish that lived longer tended to move around more.

Yet despite all the answers this study provides, Fitzpatrick hopes the work will help inspire simple questions, even for people who don’t study ecology or evolution.

“I would like people to look outside and wonder when they see an animal, how far from their homes has this individual moved and why? ” she said.

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