UNIVERSITY OF LEEDS, ALISON DUNN

A parasite (Pleistophora mulleri) roughly the size of a human blood cell can alter the behavior of freshwater shrimp (Gammarus duebeni celticus), making adults twice as likely to consume young members of their own species, according to a study published this week (March 18) in Royal Society Open Science. Although cannibalism has been demonstrated in more than 3,000 species, the study is the first demonstration of a parasite influencing the behavior.

Adult shrimp were already known to consume juveniles on occasion, a practice that contributes to the spread of the parasite via cannibalism. The parasite, which is specific to this species of shrimp, then invades the shrimp’s muscles, damaging them and driving an insatiable need for food.

To examine the impact of parasitic infection on cannibalistic behavior, scientists from the University of Leeds in England, Stellenbosch University in South Africa,...