Many a horror film has tapped into that primal fear of creepy crawly things that kill a living being by attacking it from the inside, aka, parasites. A parasite is an organism that lives in the body of a different species, and derives all its nutrients from its host. There are many different types of parasites but here’s a look at some that are the stuff of horror films.
Let’s start with parasitic wasps. There are thought to be over 200,000 different species with a variety of hosts; caterpillars, spiders, and even cockroaches. The wasps that infect cockroaches do so in a very intriguing way. The wasp spots a cockroach, and fights it until it finally stings the roach in its belly. The cockroach falls onto the floor completely paralysed. The wasp returns to the cockroach and stings the cockroach in a very specific part of its brain with a neurotoxin cocktail. The cockroach regains its consciousness and although it’s able to move it does so as if it were a zombie. The wasp grabs onto the cockroach’s antenna using its mouth and walks it into a burrow and the cockroach simply follows instructions. The wasp then lays its eggs in the cockroach’s belly after which the wasp leaves. The baby wasps hatch and feed on the insides of the cockroach until they are adults and finally emerge and at this point the cockroach dies.
Have you ever heard of anything more evil? But let us not undermine a parasite’s intelligence. Take the example of parasitic nematodes. Nemato-des or round worms are incredibly diverse with over 1,000,000 species, over 16,000 of which are thought to be parasitic. One particular type infects ants in, well, their rear end. The buttocks of the ant turns bright red and twice as big as the ant making it look like a cherry. Now why would this be evolutionarily beneficial? Imagine if a bird flies by and sees a normal ant and this infected ant, it would think the infected ant had a berry and swallow it. The only way parasitic nematodes can reproduce is within birds. And yes, a bird’s droppings help spread the nematodes.
To end on a more romantic note, there are blood flukes, also parasites but in humans. Their eggs start out in water, and on hatching, they swim around looking for humans. When the blood fluke finds a human foot wading in the shallow water, it secretes an enzyme that dissolves the skin and it swims into the bloodstream. The fluke then looks for its mate within the blood stream and they come together (they can stay this way for as long as 40 years) making eggs, and eventually making the human very sick.
Although parasites might seem deadly we have to give them credit for the way they have adapted to thrive using the planet’s organisms to their advantage. It is thought that parasites make up the majority of the earth’s species outnumbering the others by 4:1! So much for thinking we conquered the world!
The writer is a Ph.D. in Molecular Genetics and Genomics and is working on skin cancer at Novartis