Zombies Among Us…
Zombie is a relatively modern word, but the idea spans many cultures and centuries. Wherever we look, the world’s media is riddled with stories about these monstrous creatures, but they’re just stories, right? Various ideas come to mind when I say zombie. The word invokes images of iconic movies like I Am Legend, tv shows such as The Walking Dead or even historical texts about the fabled revenant.
But is there some truth in these myths?
While many believe that these creatures are mythological, their existence is much more tangible than we realise. For some unlucky creatures (such as ants, snails, frogs, and many others) becoming a zombie is a serious risk. Though not a zombie in the way we commonly understand it, the situation is definitely still very scary. If you or your loved ones are in one of these families (arachnids, crustaceans, insects, amphibians, or muridae) watch out. There are a variety of diseases and parasites that result in a zombie-esque condition afflicting these areas of the animal kingdom. I found this really shocking. Everyone has heard about zombie ants but I had no idea this was such a common phenomenon. This blog post explores some of my favourite examples of zombie afflictions.
Zombie ants on a mission
There are many zombie-like diseases in ants with one of the most well known being caused by a fungus (Ophiocordyceps unilateralis). The fungi works by controlling the mind of an ant, forcing its host to spread the fungi against its will. When a spore of the fungi finds an ant, it attaches and then works its way under the exoskeleton. After the ant is infected it is made to leave its colony in search of higher ground to better disperse the cordycep spores. When it finds a vantage point of ~25cm off the ground, it will attach itself and await death, after which the fungi will sprout and release its spores so the cycle may continue…
Dancing snails – disco zombies
When the parasitic worm (Leucochloridium paradoxum) finds an unfortunate snail, they combine to make a disco snail. The worm’s life cycle starts off as an egg in bird poop waiting to be consumed for lunch by an unsuspecting snail. It then grows inside the snail’s stomach until it becomes a strange tube-like shape, at which point it makes its way into the snail’s tentacles where the party starts. Influencing behaviour, the parasite makes these normally nocturnal snails display themselves in the day with the worm larvae pulsating to make the snail stand out (Check out this cool video). It is very effective at doing this, making the snail an attractive meal for nearby birds. After digestion, the cycle begins again with the bird relieving itself of the meal for the next unsuspecting snail to come along.
In a game of cat and mouse, zombie parasites tip the odds
Have you ever wished away fear? I know I certainly have wished for something that removes fear many times (particularly when it comes to having a due-date for a presentation). Well, this is exactly what the parasite Toxoplasma gondii does. This parasite resides in both cats & mice. It alters the immune systems of mice leading to a chemical shift in their brains, causing the mouse to love the smell of cat urine, and making them more docile. This makes the mouse more prone to chasing after cats – something we know doesn’t end very well for the mouse. In many ways, this is comparable to versing an AI in chess, but the game is rigged and there is no easy setting. The parasite doesn’t turn humans into zombies, nor does it help us with our anxiety, but we can be its hosts. That is not to say we should toss out our feline friends, but it is important to note that the parasite can be dangerous to humans (particularly for those who are pregnant).
Okay, so, when I said zombie I didn’t really mean an undead human roaming in search of a meal of live flesh or brains. However, they are very real in many other areas of the animal kingdom – with the invasion of these parasite bringing behaviour change, loss of free will, and body-wreaking havoc for these creatures. This makes me wonder, if mother nature already has zombies in her blueprints, what does the future hold for human disease?
If you’ve liked reading about this, you should check out the following links…
Or if you’d like to read more about a mutualistic relationship see here