This article was inspired and started when a colleague asked for an explanation of the life cycle of the Xenomorph from the science fiction franchise Alien by Ridley Scott. Sometimes science can be stranger than fiction and as Oscar Wilde wrote, “Life imitates art far more than Art imitates life.” Grab some tea or alcoholic beverage of choice and get comfortable because the story I am going to tell is a roller coaster of ‘something’, I am not sure what, but ‘something’.
Let’s start with our alien being the Xenomorph, which by the way MS Word recognises because there is no red line under it. According to Xenopedia – The Alien vs Predator Wiki, of course the best source of information on the topic, the life cycle of the average Xenomorph has 4 stages. If you are thinking of a butterfly’s lifecycle, take that idea and throw that out the window because the number is the only similarity these two things have in common.
The Xenomorph starts as an egg that is laid by the queen. When the egg detects an animal (or curious astronaut) nearby, it will open to reveal the next stage, the Facehugger. The Facehugger, true to its name (don’t you just love the names of animals), will seek for the face of the animal and hug it, who knew? It will then insert a tube into the mouth of the animal and insert ‘something’ into the host. That is right ladies and gentlemen, the Xenomorph is a parasite just like some wasps or that Korean film. The ‘something’ grows in its host, eventually becomes a Chestburster and bursts from the chest of the host (try to contain your horror). The Facehugger, by the way, dies shortly after depositing ‘something’. The Chestburster quickly grows into an adult worker and aids in the family business of finding new hosts and raising a happy healthy family. And you wonder why they do not teach more of this in school.
Now, notice I keep mentioning ‘something’. The Online community does not really agree as to what this ‘something’ is until the 5th movie of the franchise, Prometheus, that introduced the concept of the ‘black goo’. This goo mutates the DNA of whatever it touches and changes it quickly. This is evident as the Xenomorph that pops out of the host always carries traits from the host, like a dog/cow Xenomorph from Alien3 or the Predalien from AvP2 and games. So the online community widely agrees (and it is difficult to get the internet to agree with anything) that a version of the black goo is released into the host and quickly mutates DNA and cell function to create the Chestburster.
Why am I going into this strange tangent about fictional alien life cycles? Here we ask the question, is the Facehugger an adult that ‘lays’ the eggs of the Xenomorph? Or is it another stage in this frankly overly complicated life cycle? As a biologist, geek and smol boy who wants to know who will win a fight between king kong and Godzilla, I would say it is the latter. Why do I say so? If the Facehugger were to inject another egg or embryo into the host, I would say that it is an adult and there are 2 life cycles running next to each other to service the Xenomorph’s goal of world domination. But it does not. The Facehugger injects a part of itself that further grows into the adult. I would even go as far as to say that the Facehugger might be ANOTHER host in this drive to get the black goo into the animal.
Where, oh where, am I going with this? I have spent 600 words to talk about some science fiction abomination that in no way affects us or is present in real life. No way is there a parasite that worms its way into us like that. And what is with the over-the-top, loop de loop life cycle that uses so many hosts? Some things are just too crazy to be real right? Right? Right? *nervous laughter*
Sometimes art imitates life, and sometimes, life imitates art.
Let me introduce you to Opisthorchis viverrini or the Southeast Asian liver fluke. Never expected this to hit so close to home did you! Opisthorchis viverrini or O.V. for short is from the group of animals called flatworms (not a true worm). This lovely tiny animal can be found in, you guessed it, livers. And it is not very particular about the livers it lives in–all livers are equal in the non-existent eyes of O.V.
O.V. has 4 ‘stages’ in its life cycle, or something we can call ‘stages’ because this thing runs through hosts like we run through BBT. The usual ending point of its life cycle is in an animal, like a dog or cat, but they can and will gladly host in human livers when given the chance. Oh, did I mention that the liver fluke can cause liver cancer? Add that to the nightmare 😊
O.V. starts off its life cycle as most animals do: as an egg in a body of water which hatches into a free swimming facehugger larvae called a miracidia. The miracidia does not have a mouth and must quickly find the first host. O.V. is very picky with its first host as it has to be a specific snail called Bithynia siamensis. If lucky, the snail would do all the work by eating the O.V. eggs in the first place. Either way, once it gets into the snail, it transforms into its next form.
From one miracidia, it develops into numerous larvae called chestbursters cercariae (you know, I prefer sci-fi naming now) that will exit the snail, most likely through normal means, and return into the water body in search of its next host, a fish. O.V. is not picky about the sashimi it eats as long as it is carp. The very tiny cercariae will drill/penetrate the flesh of the fish and grow near the surface of the skin, eyes and fins of the carp. From there, they grow from cercariae to megametacarcaria and wait; patiently waiting for their last host to come by.
Time for O.V. to jump from water to land as the unlucky host fish draws the shortest stick and gets eaten by the final host, most of the time other animals, or sometimes man. Once eaten, the adult O.V. escapes from the metacercaria in the upper small intestine and makes its way into the bile duct which is connected to the liver. And here they will stay and reach sexual maturity before laying eggs and starting this over-the-top species-wide tour anew. Oh also, they are hermaphrodites. So all you need is 2 flukes to start the ball rolling, and they come in more than two flukes because they can live to up to 25 years. 25 years to accumulate flukes in you to make more flukes to meet more snails to find more fishes to encounter more livers.
Wondering how eggs get into the water to start this whole cycle? Well, the thing about having all these flukes in you is it gives you a stomachache, and that naturally leads to a visit to the little boys room. No. 2 may or may not end up in a water body somewhere that may or may not contain snails and oh look, we are back at the start.
Alright I have scared everyone enough. Fear not, you most likely do not have liver flukes living in your body. O.V. is found in and around the Mekong basin where sanitation is low and people live in and around the water. A common delicacy in the area is minced raw fish in spicy salad, Koi Pla. Proper cooking will kill any liver flukes present but when served raw, the liver flukes are not killed and thus get transferred into humans. So, if your area has a proper sewage system and you don’t eat raw carp, you are fine. From Opisthorchis viverrini, there are 2 more species of liver flukes that might just make their way into you 😊
There, that is the end of this complicated story I needed to tell. I’ve seen the Alien movies and I have also seen the fisherman eating Koi Pla. I’ve been there, I’ve seen some S***
Written by Lim Meng Hwee
Illustrated by Lim Daphne