A new study, published in the journal Royal Society Open Science, claims that parasites may be the cause of some animals to have the property of cannibalism. Upon investigating the effects of the common parasite Pleistophora mulleri, it was found that adult shrimps infected with the creature were more likely to eat their little ones than uninfected adults were. Although shrimps were already considered to be cannibals on certain occasion, the presence of parasites increases the chances of such a phenomenon.
The parasite being talked about is extremely small, and moves into the muscles of the shrimp like a spore. At first, these parasites do not make a difference as they are small in number. But millions of them eventually floods in the host and at this point, the muscles of shrimp become damaged and the animal is forced to eat more food for meeting the extra energy demand on its freeloaders.
“The parasite is quite debilitating. It takes over huge areas of the muscle, so instead of a nice transparent shrimp you get quite a chalky appearance because of muscles packed with the parasite,” said Alison Dunn, a senior author on the paper, in a press release.
Dunn told Discovery News that turning to cannibalism helps the shrimp “deal with the cost of the infection as it gains more food.” She added that earlier studies had found that the muscle damage caused by the parasites could stop the shrimps from catching their normal prey. “So perhaps cannibalism of smaller shrimp is the only way these sick animals can survive,” she said.
The teams of scientists from South Africa and UK noted that cannibalism has been seen in more than 3000 different species which includes humans (yes!) and it is often seen as a means of a “lifeboat mechanism” as it gives the organisms easy access to food in situations of dire need.
Parasitism is very common, and researchers have already found many instances of parasites which changes the behavior of their hosts’ behavior to suit their needs.
“Our research does not suggest any link between parasites and human cannibalism,” said Dunn. “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.”