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Science Behind the Fiction: Venom has nothing on real-world symbiotes and parasites

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Oct 3, 2018, 12:45 PM EDT

The history of Venom, as a character, is long, complex, and mysterious. We know it began on the planet Klyntar in a long-forgotten past. We know this creature was rejected by its peers and taken in by the Kree for study. We know it bonded with a small number of people (including Deadpool) before finding its way to Peter Parker.

Venom is a symbiote, a fictional term describing a slate of characters with similar behaviors, namely that they require a host to survive and thrive. The closest analogous creatures on Earth are symbionts, a group of organisms dependent on a mutual relationship with another organism.

Like any good symbiote, Venom attached itself to the legend of Spider-Man and became one of the most popular members of the Marvel villains gallery. The alien lifeform would eventually act as one of the central villains of Sam Raimi's Spider-Man 3 as well as the protagonist and namesake of Sony's upcoming standalone anti-hero film starring Tom Hardy, Venom.

The character's origins, however, are far more humble. In the '80s Marvel was looking to infuse its stories with some new voices and asked fans to submit ideas for its slate of characters. A Spidey fan by the name of Randy Schuller sent a letter outlining his idea for a re-imagining of Spider-Man with a new suit crafted by Reed Richards of the Fantastic Four, complete with new abilities to go with the new look. Marvel bought the idea for $220 (maybe the greatest investment in the history of pop culture), according to Schuller, and an offer to assist on a script. Talks eventually dissolved until Secret Wars changed everything in 1984, showcasing Peter Parker in his new suit.

Soon, the new suit had a mind of its own, taking control of Parker's body while he slept to combat New York's criminal element. In a state of shock over the sentient nature of his new suit, Parker rejected the symbiote, setting into motion a chain of events that would result in the emergence of one of Spider-Man's greatest villains, the introduction of Carnage, and the eventual reformation as Agent Venom.

Like most of the Marvel catalog, Venom is based loosely on the extrapolation of real-life scientific ideas and causes us to wonder how close we might be to standing at the mercy of shape-shifting aliens from beyond the stars.


It's important to note that in nature, many symbiotic relationships are mutually beneficial, aka, mutualistic. Other symbiotic relationships are categorized as being commensalistic (a relationship wherein one member gains a benefit while the other is neither harmed nor gains a benefit), or parasitic (wherein one organism gains a benefit while the other is harmed).

For instance, there are myriad microbes living on the surface and interior of your body that offer you no ill will. In fact, much of your microbiome is essential to your well being, aiding in digestion and other biological functions. In short, without those microbes, you would not be able to go about your day to day life.

A more extreme example of a beneficial parasitic relationship involves a man suffering from ulcerative colitis, an inflammatory bowel disease, and the worms he invited to live inside of him.

After years of suffering and no luck with traditional medical treatments, the anonymous patient was left with few options. That's when he came across the work of Joel Weinstock, a scientist working with parasitic worms.

Weinstock noticed that in areas where these worms are common, instances of ulcerative colitis are rare. His hypothesis was that there was a causal relationship between these two facts and he set out to test that hypothesis by feeding worm eggs to test subjects. Those test bore fruit. Patients who infected themselves with parasitic worms saw their disease symptoms improve.

P'ng Loke and colleagues from the University of California, San Francisco, set out to discover just what was happening in the digestive tract that positively impacted diseased patients when worms are introduced. They discovered that the presence of these parasites triggered regions of the bowel to generate mucus, improving the ability of the colon to heal. Weinstock suggests that this may not be a fluke, that beneficial parasitic relationships might be more common. "Humans have had parasites ever since we evolved from living in caves or swinging from trees or however it used to be, and disrupting these relationships probably had consequences," Weinstock said.

Some parasites may also be beneficial to humans and other animals in more subtle and complex ways. According to research by Pieter Johnson of the University of Colorado, Boulder, in some instances, the more parasites present in an environment the better.

Johnson's study looked specifically at a particular species of frog and found that when introduced to multiple species of parasite all at once, the actual rate of infection decreases. Moreover, when an individual frog is infected by a particularly dangerous parasite first, followed by more benign species, the impact of the dangerous parasite is reduced. It's as though competition between the parasites within a single body reduces the overall harm.

There is even some evidence that some parasitic relationships give the host organism a survival advantage. A study published in PLOS Pathogens involving brine shrimp infected with tapeworms showed that infected shrimp had more fat in their tissues and more readily survived waters tainted with arsenic. For one reason or another, being infected by a tapeworm imbued the tiny crustaceans with resistance to poison.

But not all parasitic relationships are happy times and superpowers. While a parasite does have a vested interest in the survival of the host (at least long enough to complete its reproductive cycle) that doesn't mean it won't do awful things along the way.


Charles Darwin said in The Origin of Species, "whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved." Maybe he never considered the tongue-eating louse, which feeds on the tongues of fish until they slough off and then anchors itself in their mouth like a somehow even more terrifying version of a Xenomorph's tiny mouth.

Or maybe beauty, in Darwin's mind, is in the eye of the beholder, especially if that eye is infected with Loa Loa, a parasitic nematode worm that travels the subcutaneous tissues of infected humans until it finds its way to the eye where it wriggles around, clearly visible to any onlooker.

Setting up shop inside your eye, if it can be believed, is one of the lesser crimes among nefarious parasites. Some parasites will straight up murder you in pursuit of another host who will better suit their needs.

The green-banded broodsac infects snails, engorges their eye stalks, and pulsates in a way that mimics the look of some caterpillars. It even manipulates the snail's behavior, moving it out into the open where predators like birds are likely to see it. All of this ensures the snail will quickly become snack food. The worm does this because the completion of its reproductive cycle depends on birds. The poor snail is only an intermediary step doomed to incubate and die.

Mind control of some sort isn't at all uncommon in the world of parasites. While the snail walks into the open air, flashing its pulsating eyes like beacons, it isn't alone in walking toward its doom under the influence of a parasitic passenger.

The Ladybird Parasite, a species of wasp, infects Spotted Lady Beetles by laying an egg inside their bodies. After the egg hatches, the larva chews its way through the beetle's body until it emerges to spin a cocoon between the insect's legs. The beetle, which often survives the ordeal, stands guard over the cocoon, fending off predators and protecting the predatory parasite from harm. Scientists don't fully understand why the victims exhibit this behavior but its a well-documented phenomena within the world of parasitic relationships.

Considering terrifying real-world parasites, Venom's influences don't seem all that bad. Sure, he wants you to fight and generally be a violent nuisance, but at least he doesn't curl up in your eyeballs or get you eaten alive. All things considered, it could be so much worse. Should you find yourself at the mercy of a symbiote from Klyntar, thank your lucky stars it will only turn you into a muscle-bound bully instead of colonizing you with spores, marching you the top of a tall structure, and bursting out the top of your head to infect all of your friends.

Venom hits theaters on October 5.