In Books, Comics and Films zombies are often used to shock and scare the readers and viewers. The thought of a creature that absolutely lost its free will and now is completely under the cruel control of a virus or parasite scares many people. What you would think is just a fiction of the human mind really appears in the nature. Luckily the “Zombie-Parasites” I am going to write about in this article did never infect humans. All of those parasites are only able to infect insects or animals like small fishes or birds.
In the most cases a zombie parasite appears in form of a fungus or larva. It gets into the body of specific other animal, where its damages or stimulates specific areas of the brain, which causes the hijacked animal, also called the host, to act in a certain behavior. This behavior is often self-destructive for the hosts but helps the parasite to reach its goal. A good and also extreme example of this is the tapeworm Schistocephalus solidus. The Tapeworm starts as an egg in the digestive system of a bird. After he gets dropped into the water by the bird, it develops into a larva, which gets eaten by a small crab. Inside the crab he effects it in a way that forces a strange behavior. This behavior increases the chance of the crab to get eaten by a fish. After a fish has eaten the crab, the larva develops into a worm and again influences the way the fish acts. The fish will swim really close to the surface of the water, where its most likely will be caught and eaten by a bird. Inside the bird the worm will place his eggs and at this point we are back at the beginning of the circle, where it all starts to repeat itself. However, there are other surprising ways of how animals get controlled by their environment and act like zombies. One of them is the acacia tree which takes control of the Pseudomyrmex ferrugineus-ant by producing sweet nectar, that makes the ants addicted and also damages their bodies in a way, that they can only eat the trees nectar anymore. Therefore, the ants have to stay on the tree to be able to eat something. The way the tree profits from the staying of the ants is that these protect it from weeds and also other animals.
Apocephalus borealis also known as the zombie fly.
Besides birds, fishes and ants there are many other animals and ways animals will be controlled by parasites. Other examples are Honeybees by flies, spiders by wasps, cockroaches by emerald cockroaches (which you can see in the picture on the top) and much more. These are the closest phenomena of the nature to the classical view of a zombification. However, animals and their environment are always existing together in a unique symbiosis and parasites are just one small example of the diversity of the biosystem.
Picture One: https://www.flickr.com/photos/andreaskay/48052529358 Picture Two: https://commons.wikimedia.org/wiki/File:Adult_female_Apocephalus_borealis.png Text-sources: https://en.wikipedia.org/wiki/Apocephalus_borealis https://www.mentalfloss.com/article/56018/8-parasites-create-zombie-animals https://www.thoughtco.com/parasites-that-turn-animals-into-zombies-373900