Fish Behavior Affected by Parasite

A common infection might be skewing experimental data on zebrafish.

Kerry Grens
Kerry Grens
Aug 1, 2016

FLICKR, UNDERSTANDING ANIMAL RESEARCHZebrafish swimming behavior, used to assess stress and anxiety, is impacted by the presence of a common parasite, researchers reported in the Journal of Fish Diseases last month (July 11). As Nature News reported, the infection could be confounding study results.

“The paper is great, as it raises some doubts about the way behavior may be used to study brain function in zebrafish,” Robert Gerlai, a behavioral geneticist from the University of Toronto Mississauga, told Nature. He added that the new study is not conclusive, and the techniques used to measure the swimming behavior are not as precise as continuous tracking. 

In their report, the authors stated that in 2006, the Zebrafish International Resource Center found 75 percent of labs that submitted fish for a diagnostic service had contamination with the parasite Pseudoloma neurophilia.

In a 2015 study, the researchers found P. neurophilia could affect the animals’ startle response. In their latest study, infection was associated with fish swimming closer to other fish, or shoaling. “Increased shoaling is thought to be an indicator of stress, which, along with the findings of our tap test study, could indicate that neural microsporidiosis causes the development of a high stress or anxious behavioural phenotype,” the authors wrote.

Study coauthor Sean Spagnoli of Oregon State University in Corvallis told Nature the results raise a red flag. “I haven’t seen a single paper that stated that ‘fish used were certified pathogen-free for P. neurophilia,’” Spanoli said.