Published: October 30, 2015
Science & Tech Editor
Organisms have developed a variety of ways to survive and reproduce in the world, and one of the most unique and perhaps frightening adaptations involves parasite and host interactions.
Some of the most frightening involve parasites that turn their hosts into “zombies.” These zombie organisms are not unlike the media counterparts found in shows such as “The Walking Dead.” The hosts have their behavior controlled by the parasite in a way which maximizes the possibility of transmission of the parasite. A few parasites that fall under this category are Euhaplorchis californiensis, Plagiorhynchus cylindraceus and Ampulex compressa, commonly known as the emerald cockroach wasp.
The Euhalplorchis californiensis lives in the brackish marshes of Southern California. The parasite attacks three different hosts: shorebirds, horn snails and killifish. In each case, the parasite modifies the organism’s behavior to ensure it can reproduce. Eggs from the parasite are excreted from shorebirds.
From there, horn snails ingest the parasite from the excrement. After a few life cycles, the parasite makes its way into the marshes where it latches onto the gills of killifish. Once latched onto the killifish, it infects the fish’s brain. This causes the fish to jump out of the water more frequently. By jumping out of the water more, the chance increases that a shorefish will eat it and start the life cycle all over again.
Plagiorhynchus cylindraceus is a parasitic worm that infects different songbirds, such as the robin, in North America and Europe. In order to infect the birds, these worms first infect pill bugs. The worm lives inside of the pill bugs and takes over their brain. Once the worm has control, it activates a suicide response in the pill bug.
The worm causes the pill bug to wander in the open ground rather than hiding underneath the rocks. This increases the chance that a bird of some kind will eat the bug. Once the pill bug is eaten, the worm is free to reproduce and complete its life cycle within the intestines of the bird.
The emerald cockroach wasp lives in South Asia, Africa and the Pacific Islands. The wasp uses cockroaches as a host for reproducing. The wasp stings the cockroach. Its venom then destroys the part of the cockroach’s brain responsible for the escape reflex. Once the cockroach is incapacitated, the wasp uses one of the cockroach’s antennas to lead the cockroach to the wasp’s nest. Once at the nest, the wasp lays its eggs on the abdomen of the cockroach. The cockroach is still alive at this point and cannot move to escape. Once the eggs hatch, the larva will feed on the cockroach for three to five days.
These are just a few of the many organisms in the animal kingdom that reproduce by turning another organism into a “zombie.” Each of the methods are unique but employ similar techniques to incapacitate the mind of their hosts and take control.
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