Tohru Murakami via Flickr Creative Commons // CC BY-NC 2.0
Tohru Murakami via Flickr Creative Commons // CC BY-NC 2.0

A Fish Parasite May Have Compromised Decades of Behavioral Experiments

Tohru Murakami via Flickr Creative Commons // CC BY-NC 2.0
Tohru Murakami via Flickr Creative Commons // CC BY-NC 2.0

Science’s image as an objective collection of facts took another hit this week, as researchers report that a common fish parasite may have skewed the results of thousands of behavioral science studies. They published their findings in the journal Fish Diseases.

Pseudoloma neurophilia is a teeny-tiny type of parasitic fungus called a microsporidium. Microsporidia are prolific and diverse, infecting almost every type of animal on Earth. Symptoms of a microsporidium infection vary by parasite and host species. Sometimes it’s fatal. Other times the effects are so subtle that you’d really have to be looking to notice them.

Fortunately, some scientists are looking. Researchers in the biomedicine and microbiology departments at Oregon State University (OSU) have been tracking P. neurophilia for years—specifically, its effect on Danio rerio, commonly known as the zebrafish.

If you follow science news, you’ve probably heard about zebrafish before. These unassuming little fish have become some of the most popular research animals in the world, thanks to their low-maintenance lifestyle, susceptibility to drugs and genetic changes, and enormous broods. They’re also incredibly social, which has led researchers to consider them a good model for people. Consequently, we use them to test pharmaceuticals, hunt for clues to genetic disease, and even explore the roots of human behavior.

Studies of D. rerio’s social activity often center around one specific behavior: huddling. Stressed zebrafish band together in groups called shoals, while healthy, calm fish tend to spread themselves wider apart. So researchers generally assume that clustering fish have been negatively affected in some way by experimental treatment, whether that’s a drug or a gene associated with disease.

But there’s more to it, say the OSU scientists. Their studies of P. neurophilia suggested to them that the parasite could be quietly changing zebrafish behavior. To find out, they brought 140 zebrafish into the lab and divided them into 12 tanks of 10 fish and one “sentinel tank” of 20. They set up cameras by the 12 test tanks and took still images at regular intervals.

Then, the team added water to all the tanks. Six exposure tanks, and the sentinel tank, were topped up with water from a tank of infected fish. The remaining six tanks got water from a parasite-free tank.

Once again, the researchers trained their cameras on the swimming fish, monitoring their movement. Analysis of the tank snapshots showed that fish exposed to the parasite were more likely to stick together than fish in the clean tanks. The researchers noted that fish in the parasite-treated tanks stuck even more closely together than fish in other studies who had been dosed with stress-inducing chemicals.

Postmortem examinations of fish from each group confirmed that the presence of P. neurophilia in the water was more than enough to infect a tank’s inhabitants. None of the fish from the control tanks were infected, but nearly all the fish from the parasite-treated tanks were.

The team’s earlier work has shown that infection with the microsporidium is very, very common in laboratory zebrafish populations. Lead author and veterinary surgeon Sean Spagnoli noted that some researchers might not even check to see if their fish are sick.

“I haven't seen a single paper that stated that ‘fish used were certified pathogen-free for P. neurophilia'," he told Nature.

This wouldn't be the first time scientists have overlooked a big variable. A study published earlier this year found that lab mice get chilled, stressed, and sick at normal laboratory temperatures. Another concluded that software design issues may have led to false positives in thousands of brain scan studies.

University College London geneticist Elena Dreosti isn't sure that's what's happening here. Speaking to Nature, she argued that the study’s results are statistically weak.

“Considerable additional work is needed to know if this is likely to have a significant impact on the type of behaviour research that is done by the community working with zebrafish,” she said in Nature. Other researchers have expressed doubts about the precision of measuring intra-fish distances through snapshots.

The OSU team stands by their methods and findings, but will continue to study the issue.

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These Sparrows Have Been Singing the Same Songs for 1500 Years

Swamp sparrows are creatures of habit—so much so that they’ve been chirping out the same few tunes for more than 1500 years, Science magazine reports.

These findings, published in the journal Nature Communications, resulted from an analysis of the songs of 615 adult male swamp sparrows found in six different areas of the northeastern U.S. Researchers learned that young swamp sparrows pick up these songs from the adults around them and are able to mimic the notes with astounding accuracy.

Here’s what one of their songs sounds like:

“We were able to show that swamp sparrows very rarely make mistakes when they learn their songs, and they don't just learn songs at random; they pick up commoner songs rather than rarer songs,” Robert Lachlan, a biologist at London’s Queen Mary University and the study’s lead author, tells National Geographic.

Put differently, the birds don’t mimic every song their elders crank out. Instead, they memorize the ones they hear most often, and scientists say this form of “conformist bias” was previously thought to be a uniquely human behavior.

Using acoustic analysis software, researchers broke down each individual note of the sparrows’ songs—160 different syllables in total—and discovered that only 2 percent of sparrows deviated from the norm. They then used a statistical method to determine how the songs would have evolved over time. With recordings from 2009 and the 1970s, they were able to estimate that the oldest swamp sparrow songs date back 1537 years on average.

The swamp sparrow’s dedication to accuracy sets the species apart from other songbirds, according to researchers. “Among songbirds, it is clear that some species of birds learn precisely, such as swamp sparrows, while others rarely learn all parts of a demonstrator’s song precisely,” they write.

According to the Audubon Guide to North American Birds, swamp sparrows are similar to other sparrows, like the Lincoln’s sparrow, song sparrow, and chipping sparrow. They’re frequently found in marshes throughout the Northeast and Midwest, as well as much of Canada. They’re known for their piercing call notes and may respond to birders who make loud squeaking sounds in their habitat.

[h/t Science magazine]

ZUMA Press, Inc., Alamy
5 Fascinating Facts About Koko the Gorilla
ZUMA Press, Inc., Alamy
ZUMA Press, Inc., Alamy

After 46 years of learning, making new friends, and challenging ideas about language, Koko the gorilla died in her sleep at her home at the Gorilla Foundation in Woodside, California on June 21, 2018. Koko first gained recognition in the late 1970s for her ability to use sign language, but it was her friendly personality that made her a beloved icon. Here are five facts you should know about the history-making ape.


Francine "Penny" Patterson, then a graduate student at Stanford University, was looking for an animal subject for her inter-species animal communication experiment in the early 1970s when she found a baby gorilla at the San Francisco Zoo. Originally named Hanabiko (Japanese for "fireworks child," a reference to her Fourth of July birthdate), Koko took to signing quickly. Some of the first words Koko learned in "Gorilla Sign Language," Patterson's modified version of American Sign Language, were "food," "drink," and "more." She followed a similar trajectory as a human toddler, learning the bulk of her words between ages 2.5 and 4.5. Eventually Koko would come to know over 1000 signs and understand about 2000 words spoken to her in English. Though she never got a grasp on grammar or syntax, she was able to express complex ideas, like sadness when watching a sad movie and her desire to have a baby.


Not only did Koko use language to communicate—she also used it in a way that was once only thought possible in humans. Her caretakers have reported her signing about objects that weren't in the room, recalling memories, and even commenting on language itself. Her vocabulary was on par with that of a 3-year-old child.


Koko was the most famous great ape who knew sign language, but she wasn't alone. Michael, a male gorilla who lived with Koko at the Gorilla Foundation from 1976 until his death in 2000, learned over 500 signs with help from Koko and Patterson. He was even able to express the memory of his mother being killed by poachers when he was a baby. Other non-human primates have also shown they're capable of learning sign language, like Washoe the chimpanzee and Chantek the orangutan.


Koko received many visitors during her lifetime, including some celebrities. When Robin Williams came to her home in Woodside, California in 2001, the two bonded right away, with Williams tickling the gorilla and Koko trying on his glasses. But perhaps her most famous celebrity encounter came when Mr. Rogers paid her a visit in 1999. She immediately recognized him as the star of one of her favorite shows, Mister Rogers' Neighborhood, and greeted him by helping him take off his shoes like he did at the start of every episode.


Koko was never able to have offspring of her own, but she did adopt several cats. After asking for a kitten, she was allowed to pick one from a litter for her birthday in 1985. She named the gray-and-white cat "All Ball" and handled it gently as if it were her real baby, even trying to nurse it. She had recently received two new kittens for her 44th birthday named Ms. Gray and Ms. Black.


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