F Rosa Rubicondior: Malevolent Designer News - How a Parasite is Designed to Make its Host Commit Suicide

Wednesday 30 June 2021

Malevolent Designer News - How a Parasite is Designed to Make its Host Commit Suicide

The life cycle of the hairworm
After hatching in the water, hairworm larvae parasitize aquatic insects and form a cyst in the hosts’ body cavity. After the aquatic insect has grown wings, the hairworm is transported from an aquatic environment to a terrestrial environment. If the aquatic insect is consumed by a mantid, the hairworm grows inside the mantid’s body until it reaches maturity and causes its host to enter the water. Once the mantid is in the water, the hairworm escapes back into the aquatic environment to reproduce, and its lifecycle ends.
Parasites manipulate praying mantis’s polarized-light perception, causing it to jump into water. | Research at Kobe

Readers of my popular, illustrated book, The Malevolent Designer: Why Nature's God is not Good will already be familiar with several examples of a parasite turning its host into an automaton, where the host is manipulated by the parasite to behave in ways beneficial to the parasite but detrimental to the host, often resulting in the death of its victim.

In fact, viewed as a memetic mind virus, religions which encourage and inspire self-sacrifice can be seen as examples of this manipulative mind-control too. They do nothing to enhance the wellbeing of their victim in this respect and serve only to benefit the religion that induces this behaviour, using the cultural assumptions that self-sacrifice for a cause is to be admired and indicates the validity of the religion that induces it.

This example, discovered by researchers at Kobe University, is yet another to be added to that long list. They have discovered how a nematode or hairworm manipulates the behaviour a praying mantis host to jump into water where the hairworm can escape from its body and produce larvae which infect the aquatic larval stage of flying insects, in response to polarized light reflected off the surface of water.

As the Kobe University News release explains, the biological background to this is:
Normally, an animal’s morphology and behavior are regulated in order to benefit the individual’s survival and reproduction. However, approximately 40% of terrestrial organisms are parasites and it is said that all wild animals have at least one type of parasite. In other words, various anatomical changes and behaviors observed in wild animals could be strongly influenced by parasites. Remarkably, there are many species of parasite that can alter aspects of their host’s morphology and behavior (host manipulation) for their own benefit (i.e. to increase the parasites’ fitness). Parasites that manipulate their hosts are a good example of an extended phenotype*2 and have come to fascinate many biologists.

A known phenomenon whereby the parasite manipulates the host’s behavior can be seen in hairworms. Hairworms are nematomorph parasites that live inside insects such as mantids and camel crickets (referred to as the ‘host’). However, hairworms reproduce in rivers and ponds, so in order to move themselves into these environments, they manipulate the host so that it jumps into the water. Previous research has suggested that the brightness of reflected light (light intensity) on the surface of the water attracts the host, causing it to fall in. However, aside from the surfaces of rivers and ponds, there are many other luminous environments and instances in nature, including forest openings, bright sandy habitats and grasslands reflecting sunlight or moonlight. If the host were attracted to every single occurrence of bright light in nature, then the host manipulation would fail. Therefore this behavior of entering the water cannot be sufficiently explained in terms of mere attraction to the light.

Polarized light* is a type of light where the electric field of the light wave oscillates in only one direction. The light reflected off the surface of a body of water contains a lot of horizontally polarized light, and it has been shown in recent years that many arthropods use this horizontally polarized light to either seek out or avoid water. The researchers hypothesized that host, manipulated by the hairworm, is attracted by the horizontally polarized light and enters the water...

In nature, animals have evolved diverse abilities to perceive the intensity, color, shade and polarization of light. These research results show, for the first time in the world, that parasites can skillfully manipulate these abilities to cause the host animal to exhibit behaviors that benefit the parasite.

*Polarized light
The light that radiates from The Sun is unpolarized. However, when this light is reflected (for example, by molecules and objects above the atmosphere or by the surface of a body of water), the direction of some of the electromagnetic waves becomes linearly polarized (i.e. they run in one direction), resulting in the light being polarized to a degree.
The team's findings are published in Current Biology:
A wide range of parasites manipulate the behaviours of their hosts in order to complete their life cycle 1 . Alteration of phototaxis is thought to be involved in host manipulation in many cases 2 ,3 . However, very little is known about what features of the light (intensity, spectrum, polarization) alter behaviour. Here we report that arboreal mantids (Hierodula patellifera) infected by nematomorph parasites (Chordodes sp.) are attracted to horizontally polarized light, which could induce the mantids to enter water, where the parasites can then emerge and reproduce. In a two-choice test, infected mantids were attracted to horizontally but not vertically polarized light. Uninfected mantids were not attracted to either. In a field experiment, 14 infected mantids entered a deep pool, where the water surface strongly reflected horizontally polarized light. By contrast, only two mantids entered a shallow pool, where the surface reflection had higher light intensity but weaker polarization. To our knowledge, this is the first study demonstrating that a manipulative parasite can take advantage of its hosts’ ability to perceive polarized light stimuli to alter host behaviour.

Unlike religions which, as I mentioned above, can induce self-sacrificial behaviour by influencing the thinking of their host, no-one would seriously imagine that this self-sacrificial behaviour by mantids (and, incidentally by crickets which behave the same way when parasitised by a nematode) is something to be admired or an indication that it is somehow a 'good thing' to be parasitised by a mind-controlling nematode.

Just as with religion, of course, Creationists must attribute this ability of a nematode to control its hosts to the deliberate design of an intelligent [sic] designer. The mystery is, why these religious fundamentalist behave in this self-sacrificial way, willingly displaying the fact that they have been skilfully manipulated by parasitic frauds who sell them the childish notion of design by a magic sky man, despite the lack of evidence for such an entity, and all the evidence for an amoral, undirected, purposeless natural process being the cause of it.

An effect of this mind-control appears to be wilful scientific illiteracy combined with a lack of the critical thinking skills and the necessary self-awareness to realise they are portraying the object of their devotion as a sadistic monster, capable of designing horrors like these mind-controlling parasites, who hates its creation so much that it spends a great deal of time and effort designing ever-more imaginative ways to make it suffer.

You really would think that genuine devotees of this supposed creator god would do more to counter the harm that Creationists are doing to their religion, but perhaps they are aware that doing so would entail accepting that their holy book and the basis of their religion is primitive bunkum and irredeemably flawed as a source of truth, so could not have been inspired by an omniscient creator god - facts which render is useless as the basis of a religion.

Thank you for sharing!

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