Parasites Linked to Cannibalism

A tiny creature makes shrimp more likely to eat their own

William Brady / Retna/Retna Ltd./Corbis

Ever wonder why some animals are more prone to eating their own kind? New research could hold an answer—it turns out that parasites may drive their hosts to cannibalism.

A team of researchers from the University of Leeds, intrigued by how pervasive cannibalism is in environments where resources are limited, wondered if parasites might be linked. So they studied Pleistophora mulleri, a microscopic spore-forming parasite, and its effects on Gammarus duebeni celticus, an endangered river shrimp native to Ireland.

After collecting shrimp from Downhill River in Northern Ireland, they separated them out based on whether or not they were infected with parasites. Then the real fun began: they placed uninfected juvenile shrimp in the vicinity of adults and watched them prey. They found that adults who had parasites ate the juveniles significantly more often than those who didn’t…and adults who harbored parasites also had higher feeding rates.

Their findings are among the first to link parasites and cannibalism, Discovery News reports. Mandy Bunke, the study’s lead, tells Discovery News that when parasites invade their hosts, they damage their muscles and need more and more nutrients to survive. And another author noted that cannibalism could be the only choice for infected animals:

Senior author Alison Dunn of the University of Leeds told Discovery News that “being more cannibalistic might help the host to deal with the cost of the infection as it gains more food.”

“Interestingly,” she continued, “we have also found in earlier work that infected shrimp may be able to catch and eat less prey of other animal species, so perhaps cannibalism of smaller shrimp is the only way these sick animals can survive.”

The team hopes their research can help scientists better understand factors that affect a species’ survival in changing environments. Given that parasites have the potential to control animals’ nervous systems and harm humans, there’s no wonder the microscopic organisms are having a research heyday.

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