Tiny Parasite Turns Shrimp Into Voracious Cannibals

Posted on March 18, 2015

A tiny parasite turns shrimp into voracious cannibals. Cannibalism significantly increased in freshwater shrimp infected with Pleistophora mulleri. The tiny parasite is about the size of a human red blood cell. The parasitized shrimp also become more voracious and consumed their victims much more quickly than shrimp that were not infected. A pair of Gammarus duebeni celticus (shrimp) are pictured above.

The research was conducted by scientists at at the University of Leeds, Queen's University Belfast and Stellenbosch University in South Africa. Dr. Alison Dunn from Leeds lead the study. Dr. Dunn says, "Cannibalism is actually fairly common in nature. Our work is the first study to ask if cannibalism is affected by being parasitised."

Mandy Bunke, a PhD student at the University of Leeds, says, "Although the parasite is tiny--similar in size to a human red blood cell--there are millions of them in the host muscle and they all rely on the host for food. This increased demand for food by the parasites may drive the host to be more cannibalistic."

Gammarus duebeni celticus is a shrimp species native to Great Britain. The researchers say it is being replaced in Irish waterways by an invasive shrimp species, Gammarus pulex. It is possible the parasite described in this study is partly responsible by weakening Gammarus duebeni's resistance.

Could a parasite turn humans into cannibals? This seems unlikely according to the researchers. Dr. Dunn says, "Our research does not suggest any link between parasites and human cannibalism. There is evidence that parasites can affect human behaviour. A study led by Dr Glenn McConkey, also of the University of Leeds Faculty of Biological Sciences, has shown that the parasite Toxoplasma gondii directly affects the chemistry of the human brain. However, cannibalism for the shrimp, unlike in humans, is a significant source of food even in uninfected animals. It seems unlikely that a parasite would be under evolutionary pressure to influence cannibalism in humans."

A research paper on the shrimp parasite can be found here in the journal, Royal Society Open Science.

Photo: Alison Dunn

ANIMALS