We all know the small, blue and white striped zebra fish from the domestic aquarium or aquazoo. Because of their elongated shape and their beautiful colour pattern they catch our eye very quickly. What the zebrafish was less known for so far: hyperactivity. This could now change, because at the beginning of this month a new publication was published in which the swimming behaviour of adult zebrafish was investigated. It was found that zebrafish swimming in waters with increased microplastic stress became hyperactive.
In the study, adult zebrafish were exposed to polystyrene microplastics with a size of 5 micrometers in concentration ranges from 0.001 to 20 milligrams per liter. The fish were thus surrounded by microplastic particles, similar to the situation in some areas of our environment. The results showed that the microplastics accumulate in both the digestive tract and the gills, but not in the brain. Although no obvious damage to the intestine was found, the research group found that the thickness of the muscularis layer in the fore intestine decreased by 32 percent after the fish were exposed to the microplastics. The researchers also found that the zebrafish became hyperactive the longer they were exposed to the increased microplasty concentration: their swimming distance was greater at 1.3 to 2.4 folds than that of the control fish without microplasty. They also remained in an active swimming state for much longer. The study suggests that microplastic particles cause behavioural anomalies.