Zombies Exist in Nature

Posted: June 6, 2012 in news
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Continueing on the previous posts: Is a “Zombie Virus” Possible and More Real-life Zombie Concerns, it seems necessary to point out a few more examples of how zombies already exist in nature. First on the list is a wasp, Ampulex compressa to be precise, that uses venom and its stinger to control cockroaches.

The wasp slips her stinger through the roach’s exoskeleton and directly into its brain. She apparently use ssensors along the sides of the stinger to guide it through the brain, a bit like a surgeon snaking his way to an appendix with a laparoscope. She continues to probe the roach’s brain until she reaches one particular spot that appears to control the escape reflex. She injects a second venom that influences these neurons in such a way that the escape reflex disappears.

From the outside, the effect is surreal. The wasp does not paralyze the cockroach. In fact, the roach is able to lift up its front legs again and walk. But now it cannot move of its own accord. The wasp takes hold of one of the roach’s antennae and leads it–in the words of Israeli scientists who study Ampulex–like a dog on a leash.

The zombie roach crawls where its master leads, which turns out to be the wasp’s burrow. The roach creeps obediently into the burrow and sits there quietly, while the wasp plugs up the burrow with pebbles. Now the wasp turns to the roach once more and lays an egg on its underside. The roach does not resist. The egg hatches, and the larva chews a hole in the side of the roach. In it goes.

That’s right kids, zombie roaches controlled by wasps. And this is real.

No doubt that is pretty disturbing, but this next example is even more bizarre. A parasitic worm, Euhaplorchis californiensis, is known to infect certain types of fish so that they thrash around on the surface of the water making them more vulnerable to predators and, in turn, more likely to propagate the spread of the parasitic species.

California killifish (Fundulus parvipinnis) infected with the brain-encysting trematode Euhaplorchis californiensis display conspicuous swimming behaviours rendering them more susceptible to predation by avian final hosts. Heavily infected killifish grow and reproduce normally, despite having thousands of cysts inside their braincases. This suggests that E. californiensis affects only specific locomotory behaviours. We hypothesised that changes in the serotonin and dopamine metabolism, essential for controlling locomotion and arousal may underlie this behaviour modification. We employed micropunch dissection and HPLC to analyse monoamine and monoamine metabolite concentrations in the brain regions of uninfected and experimentally infected fish. The parasites exerted density-dependent changes in monoaminergic activity distinct from those exhibited by fish subjected to stress. Specifically, E. californiensis inhibited a normally occurring, stress-induced elevation of serotonergic metabolism in the raphae nuclei. This effect was particularly evident in the experimentally infected fish, whose low-density infections were concentrated on the brainstem. Furthermore, high E. californiensis density was associated with increased dopaminergic activity in the hypothalamus and decreased serotonergic activity in the hippocampus. In conclusion, the altered monoaminergic metabolism may explain behavioural differences leading to increased predation of the infected killifish by their final host predators.

The TL;DNR version is: the worm infects the fishes’ brains and they flop around on the surface so more birds eat them and spread the worm even further. Yes, zombie fish already exist.

Finally, another type of wasp uses a species of caterpillar to act as a host for its developing offspring.

The fun begins when a female Glyptapanteles wasp comes across a potential host–a moth known as Thyrinteina leucocerae. The wasp inserts a stinger-like probe into the caterpillar’s gut body cavity and injects dozens of eggs. The eggs hatch and grow into wasp larvae, which feed on the still-living host as it continues munching on leaves. The caterpillars even moult and pass through three or four stages with the parasites lurking inside them. Finally, when the wasps have finished their living feast, about 80 of them drill escape holes and crawl out of the caterpillar. They move a few inches away, where they spin cocoons on a twig or leaf, where they will develop into adults.

No, you did not read that wrong. The zombie caterpillar continues “living”, albeit in a metamorphosed fashion, after the entire ordeal. Isn’t that pretty much the definition of a zombie?

Stay tuned, this is just getting started and there will be much more to come…

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