Fruit Flies Are Essential to Science. So Are the Workers Who Keep Them Alive.

The rooms that make up the Bloomington Drosophila Stock Center at Indiana University are lined wall to wall with identical shelves. Each shelf is filled with uniform racks, and each rack with indistinguishable glass vials.

The tens of thousands of fruit fly types within the vials, though, are each magnificently different. Some have eyes that fluoresce pink. Some jump when you shine a red light on them. Some have short bodies and iridescent curly wings, and look “like little ballerinas,” said Carol Sylvester, who helps care for them. Each variety doubles as a unique research tool, and it has taken decades to introduce the traits that make them useful. If left unattended, the flies would die in a matter of weeks, marooning entire scientific disciplines.

Throughout the Covid-19 pandemic, workers across industries have held the world together, taking on great personal risk to care for sick patients, maintain supply chains and keep people fed. But other essential jobs are less well-known. At the Stock Center dozens of employees have come to work each day, through a lockdown and afterward, to minister to the flies that underpin scientific research.

To most casual observers, fruit flies are little dots with wings that hang out near old bananas. But over the course of the last century, researchers have turned the insect — known to science as Drosophila melanogaster — into a sort of genetic switchboard. Biologists regularly develop new “strains” of flies, in which particular genes are turned on or off.

Studying these slight mutants can reveal how those genes function — including in humans, because we share over half of our genes with Drosophila. For instance, researchers discovered what is now called the hippo gene — which helps regulate organ size in both fruit flies and vertebrates — after flies with a defect in it grew up to be unusually large and wrinkly. Further work with the gene has indicated that such defects may contribute to the unchecked cell growth that leads to cancer in people.

Other work with the flies has shed light on diseases from Alzheimer’s to Zika, taught scientists about decision-making and circadian rhythms and helped researchers using them to win six Nobel Prizes. Over a century of tweaking fruit flies and cataloging the results has made Drosophila the most well-characterized animal model we have.

It’s a big role for an unassuming bug. “When I try and tell people what I do, the first thing they usually say is, ‘Why would you keep fruit flies alive? I try and kill them!’” said Ms. Sylvester, who has been a stockkeeper at Bloomington since 2014.

If a few hitchhike to her house from the grocery store, her kids razz her, she added: “‘Mom, you brought your co-workers home from work again.’”

Drosophila melanogaster, true to form, on a rotting banana.
Bob Gibbons/Alamy
Kaiti Sullivan for The New York Times
Kaiti Sullivan for The New York Times

The Bloomington Drosophila Stock Center is the only institution of its kind in the United States, and the largest in the world. It currently houses over 77,000 different fruit fly strains, most of which are in high demand. In 2019, the center shipped 204,672 vials of flies to labs in 49 states and 54 countries, said Annette Parks, one of the center’s five principal investigators.

It is “one of the jewels we have in the community,” said Pamela Geyer, a stem cell biologist at the University of Iowa who has been ordering flies from the stock center for 30 years.

Other model organisms can be frozen at particular life stages for long-term storage; lab freezers the world over hold mouse embryos and E. coli cultures. But fruit flies can’t go on ice. Caring for the creatures means regularly “flipping” them: transferring them from an old vial to a clean one that has been provisioned with a dollop of food. Quarantined with other members of their strain, the flies mate and lay eggs, which hatch, pupate and reproduce, continuing the cycle.

“We have strains in our collection that have been continuously propagated like that since around 1909,” across generations and institutions, said Cale Whitworth, another stock center principal investigator. To keep their millions of Drosophila flipped and happy, the center employs 64 stockkeepers, as well as one media preparator — think fly-food cook — as well as a kitchen assistant and five dishwashing personnel.

At the stock center, as everywhere, the pandemic’s first stirrings felt ominous. “I remember joking with people, ‘We’re the people in the beginning of the dystopian novel, and we don’t know what’s coming yet,’” Ms. Sylvester said.

As case numbers rose, Dr. Whitworth packed a go-bag with a pillow and a toothbrush, imagining the worst. “I was in the full-on, ‘Everyone’s sick, last man on Earth’ type thing,” he said. “Like, ‘How many flies can I flip in a 20-hour period, sleep for four hours, and keep flipping the next day?’”

Instead, when Indiana University shut down on March 15, the stock center stayed open.

Kevin Gabbard, the fly-food chef, did an emergency shop. Although they eat the same thing every day — a yeasty mash of mostly corn-based products — flies can be picky. Mr. Gabbard, risking nothing, ordered two months’ worth of their preferred brands. “You think cornmeal’s cornmeal,” he said. “But it’s not if it’s not right.”

Kaiti Sullivan for The New York Times
Kaiti Sullivan for The New York Times
Kaiti Sullivan for The New York Times

The co-directors developed a more robust Hail Mary plan that, if absolutely necessary, would allow them to “keep most of the flies alive with just eight people,” said Dr. Whitworth. They also decided to halt all shipments, focusing their energy on fly care.

On March 26, flies stopped leaving the building — and almost immediately, supportive messages began rolling in. “You are all amazing,” read one email. “The fly community is strong because of the phenomenal work that you do.”

Around the same time, the employees had a choice to make. Deemed essential workers, they were authorized to come to campus. The university guaranteed them full pay even if they decided to stay home, or time-and-a-half for coming in. (The center covers its costs through a combination of federal National Institutes of Health grants and its own earnings from fly sales.)

The vast majority chose to continue working, said Dr. Whitworth — even though the job was suddenly quite different. The center is usually a very social workplace, with birthday parties and group lunches. Hours are normally flexible, a big selling point for employees, many of whom are parents or students, or have retired from full-time work.

Now people work in masks, often in separate rooms. Shifts in one of the center’s buildings became strictly scheduled to avoid overlap. “You can be working alone for quite a while, maybe all day,” said Roxy Bertsch, who has been a stockkeeper since 2018.

And for the first several weeks, the stockkeepers — many of whom perform additional duties, such as packing, shipping and training — spent all their time flipping flies, which is monotonous and hard on the hands. “All we were doing was coming in, feeding flies and leaving,” Mrs. Bertsch said.

Kaiti Sullivan for The New York Times
Kaiti Sullivan for The New York Times
Kaiti Sullivan for The New York Times

But she kept going back. After her son was potentially exposed to the coronavirus, and she had to self-quarantine, she counted down the 14 days until she could return.

“There is no way you are keeping me from work if I could be here,” she said.

Ms. Sylvester specializes in caring for flies whose mutations mean they need extra TLC. She also worked full-time throughout the shutdown, buoyed by concern for her charges. “I mostly just love the flies and don’t want them to die,” she said. “I never thought I would love larvae so much.”

In mid-May, the center began shipping stocks again. Dr. Parks passed along another batch of messages, many of them now tinged with relief.

“Feels like Christmas,” tweeted a lab at Denmarks’ Aarhus University, with a photo of a box of vials.

One message earlier in the spring from Tony Parkes, a biologist at Nipissing University in Ontario, had extolled all of those “who go about their work with few accolades, but on whom everyone counts as a foundational backbone.”

Kaiti Sullivan for The New York Times
Kaiti Sullivan for The New York Times
Kaiti Sullivan for The New York Times

When Dr. Parkes’s lab paused, he spent some of his unexpected down time thinking about the stock center. It is an equalizer, he said, enabling even small labs to tackle big questions “without requiring vast resources.”

It also allows researchers to literally share their discoveries with each other. “You don’t have to maintain your own library to have access to all of that information,” he said, because the stock center is “there whenever you wish.”

The people who keep the center running think about this, too. “It means a lot to know that you’re a part of that,” said Mrs. Bertsch.

But it adds some pressure. “We all feel this big weight to make sure the stock center is there for everyone,” said Dr. Whitworth.

The pandemic continues, of course, and more obstacles loom. Although the fall semester passed without incident, cases are rising in the area, increasing the potential for another shutdown. Mail delays, both domestic and overseas, have prompted the center to suggest that their customers turn to private carriers — flies perish if kept in transit too long.

Although they are no longer being paid extra, everyone keeps coming to work. And even if things take a turn, Dr. Whitworth is ready. “I never unpacked my bag,” he said. “It’s still sitting in the closet.”

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