Mantis Hierodula sp. with two Chordodes mizoramensis emerging
One of the more gruesome aspects of many parasites is their ability to take control of their hosts so the host participates in its own destruction, for the benefit of the parasite.
I wrote extensively about these relationships in by popular, illustrated book, The Malevolent Designer: Why Nature's God is not Good, to illustrate the fact that the creator god creationists purport to worship has to be regarded as a pestilential, sadistic monster forever devising more and more nasty ways to make its creation suffer, for no apparent reason other than the pleasure of watching the suffering.
An example I used was the parasitic nematodes known as horsehair worms that live for part of the life-cycle in an insect such as a cricket or mantis, and, when mature, it induces it to seek out and jump into water where it either drowns or gets consumed by a fish. If the former, it emerges from the dead or dying body of its host and adopts a free-living life in the water; if the latter, it passes through the fish unharmed and emerges into the water via that route.
My AI source describes them thus:
Tell me all about the Chordodes horsehair worms and their life-cycle. Chordodes, commonly known as horsehair worms or Gordian worms, are a group of parasitic nematode worms belonging to the phylum Nematomorpha. They are intriguing creatures known for their peculiar life cycle and ability to emerge from the bodies of various insect hosts. Here is some information about Chordodes horsehair worms and their life cycle:The mystery for science was how the parasites control their hosts’ behaviour to induce them to do something they would never normally do. Research has shown that they do it by producing proteins which are very similar to proteins produced by their hosts own neurological centres, but the mystery was how the worms had acquired the genes to produce these proteins which so closely mimic the hosts own proteins.In conclusion, Chordodes horsehair worms have a fascinating life cycle that involves a parasitic phase within insect hosts and a free-living phase in water. Their ability to manipulate the behavior of their hosts and their unique life cycle make them a subject of interest in the field of biology.
- Appearance: Horsehair worms are long, thin, and thread-like worms that resemble strands of hair. They are typically dark brown or black and can grow to be several inches in length, although some species can reach up to two feet or more.
- Life Cycle:
The life cycle of Chordodes horsehair worms is quite fascinating and involves a parasitic phase and a free-living phase. Here's how it works:
- Parasitic Phase:
- Eggs: Adult horsehair worms lay their eggs in or near water bodies, such as ponds, streams, or puddles.
- Larvae: The eggs hatch into larvae, which are microscopic and free-swimming in the water.
- Infection of Host: Larvae are then ingested by a variety of insects, including grasshoppers, crickets, beetles, and mantises, while these insects are drinking or feeding in the water.
- Development in Host: Once inside the host insect, the horsehair worm larvae grow and develop, often coiling up in the host's body cavity.
- Emergence: After reaching a certain size, the mature horsehair worm causes changes in the host's behavior, driving it to seek out water. The host insect then dies and releases the adult worm into the water.
- Free-Living Phase:
- Reproduction: In the water, the adult horsehair worm reproduces, laying eggs to start the cycle anew.
- Behavior and Emergence:
One of the most intriguing aspects of horsehair worms is their ability to manipulate the behavior of their host insects. When ready to emerge from the host, the horsehair worm releases chemicals or triggers changes in the host's nervous system, making it seek water. This behavior is often referred to as "mind control."- Habitat:
Horsehair worms are typically found in freshwater environments, including ponds, streams, and puddles. They need water for reproduction and the initial stages of their life cycle.- Predators and Diet:
As adults, horsehair worms are free-living and primarily feed on detritus and organic matter in their aquatic environment. They are relatively harmless to humans and animals once they emerge from their insect hosts.
One would expect an intelligent [sic] designer, bent on another piece of malevolent design, to simply give the worms the same genes as those it gave the insects, but as we've come to expect of creationism’s putative designer, it never does things simply, the way a real intelligent designer does. Instead, in this case, at some point in the history of this parasite-host relationship, the worms acquired insect genes by horizontal gene transfer - a rare method of increasing the genome in multicellular species, but common in singles-celled organisms.
This mystery was solved by a team led by Tappei Mishina at the RIKEN Center for Biosystems Dynamics Research (BDR), Japan, as their news release explains:
Stolen genes allow parasitic control of behaviorAlthough the main body of the paper in Current Biology is behind an expensive paywall, the author's highlights and summary are freely available:
A team led by Tappei Mishina at the RIKEN Center for Biosystems Dynamics Research (BDR) has discovered that parasites manipulate their hosts using stolen genes that they likely acquired through a phenomenon called horizontal gene transfer. The study was published in the scientific journal Current Biology on October 19.
Many parasites manipulate the behavior of their hosts to ensure their survival and ability to reproduce. Horsehair worms display one of the most sophisticated examples of this type of control of behavior. Horsehair worms are born in water and use aquatic insects like mayflies to hitchhike to dry land, where they sit tight until they are eaten by terrestrial insects such as crickets or mantises. Once a horsehair worm reaches these hosts, it starts growing and manipulates the host’s behavior. The matured horsehair worm finally induces the host to jump into water, often to the host’s ultimate demise, so it can complete its life mission and reproduce.
Previous studies have suggested that horsehair worms hijack their hosts’ biological pathways and increase movement towards light, which leads the hosts to approach water. Scientists believe this is accomplished with molecules that mimic those of the hosts’ central nervous systems, but exactly how these parasites developed this kind of molecular mimicry has remained a mystery.
To answer this question, the researchers analyzed whole-body gene expression in a Chordodes horsehair worm before, during, and after manipulating its mantis host. They found over 3,000 hairworm genes that were expressed more when hosts were being manipulated, and 1,500 hairworm genes that were expressed less. On the other hand, gene expression in the mantis brains did not change, and in fact could not be distinguished from that found in uninfected mantises. These results indicate that horsehair worms produce their own proteins for manipulating their hosts’ nervous systems.
The researchers next searched a protein database to explore the origins of the genes that Chordodes horsehair worms use to manipulate mantises. “Strikingly, many of the horsehair worm genes that could play important roles in manipulating their hosts were very similar to mantid genes, suggesting that they were acquired through horizontal gene transfer,” says Mishina. Horizontal gene transfer is a biological process in which genes are transferred from one organism to another, but not through reproduction. It can have significant evolutionary consequences, allowing organisms to acquire new genes or functions rapidly, potentially helping them adapt to new environments or lifestyles.
Further analysis supported the idea that the molecular mimicry seen in the Chordodes horsehair worms is likely the result of horizontal gene transfer from mantises. In particular, over 1,400 Chordodes horsehair worm genes were found to match those in mantises, but were absent or very different from species of horsehair worms that do not use mantis hosts. The authors conclude that the numerous mimicry genes that they identified are likely the result of multiple horizontal gene-transfer events from various mantid species during the evolution of hairworms. These genes, particularly those associated with neuromodulation, attraction to light, and circadian rhythms, appear to play a role in host manipulation.
Horizontal gene transfer is one of the primary ways that bacteria evolve to resist antibiotics. Mishina believes that as we find more examples of horizontal gene transfer between multicellular organisms, we will gain insight into this phenomenon as well as evolution in general. “The many cases of horizontal gene transfer that we have found in the hairworm can be a good model for study,” Mishina says. “Using this model, we hope to identify the mechanisms underlying horizontal gene transfer and advance our understanding of evolutionary adaptation.”
(A) The number of top hit genes in the database search for each species with sequences from the Chordodes hairworm. The majority of the genes in the hairworm used in this study are not the most similar to genes of other hairworms (Paragordius and Gordius), but to those of the host mantid. (B) Relationships between candidate HGT genes and differentially expressed genes (DEGs) during host manipulation by hairworms.
Horsehair worms use mantids as definitive hosts. After maturing in a mantis, they manipulate their hosts to enter water bodies where the parasites reproduce.
Photo by Takuya Sato.
HighlightsWhat creationists might like to think about here, if that's not asking too much of them, is:Summary
- Explored molecular basis of nematomorph-driven water-entry behavior of mantids.
- Nematomorph transcriptomes were exclusively changed during host manipulation.
- Numerous possible host-derived horizontal gene transfer (HGT) events were discovered.
- Candidate HGT genes were frequently up-regulated during host manipulation.
To complete their life cycle, a wide range of parasites must manipulate the behavior of their hosts. 1 This manipulation is a well-known example of the “extended phenotype, 2 ” where genes in one organism have phenotypic effects on another organism. Recent studies have explored the parasite genes responsible for such manipulation of host behavior, including the potential molecular mechanisms. 3 ,4 However, little is known about how parasites have acquired the genes involved in manipulating phylogenetically distinct hosts. 4 In a fascinating example of the extended phenotype, nematomorph parasites have evolved the ability to induce their terrestrial insect hosts to enter bodies of water, where the parasite then reproduces. Here, we comprehensively analyzed nematomorphs and their mantid hosts, focusing on the transcriptomic changes associated with host manipulations and sequence similarity between host and parasite genes to test molecular mimicry. The nematomorph’s transcriptome changed during host manipulation, whereas no distinct changes were found in mantids. We then discovered numerous possible host-derived genes in nematomorphs, and these genes were frequently up-regulated during host manipulation. Our findings suggest a possible general role of horizontal gene transfer (HGT) in the molecular mechanisms of host manipulation, as well as in the genome evolution of manipulative parasites. The evidence of HGT between multicellular eukaryotes remains scarce but is increasing and, therefore, elucidating its mechanisms will advance our understanding of the enduring influence of HGT on the evolution of the web of life.
Mishina, Tappei; Chiu, Ming-Chung; Hashiguchi, Yasuyuki; Oishi, Sayumi; Sasaki, Atsunari; Okada, Ryuichi; Uchiyama, Hironobu; Sasaki, Takeshi; Sakura, Midori; Takeshima, Hirohiko; Sato, Takuya
Massive horizontal gene transfer and the evolution of nematomorph-driven behavioral manipulation of mantids
Current Biology. doi: 10.1016/j.cub.2023.09.052
© 2023 Elsevier Inc.
Reprinted under the terms of s60 of the Copyright, Designs and Patents Act 1988.
- The fact that, if this really is the work of an intelligent [sic] designer, not only is it evidence of the needless complexity commonly seen in evolved systems but of the fact that such a designer can only be regarded as a malevolent, sadistic monster and a far cry from the supposedly all-loving Christian god.
- The fact that a massive amount of new information was acquired by the horsehair worms' genomes by an entirely natural process, despite the creationist dogma that no new information can arise without the assistance of a magic man doing magic.
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