Terrifying Parasitic Worm ‘Steals’ Genes From Its Unsuspecting Host To Gain Mind Control

A parasite called horsehair worm (Chordodes formosanus) relies on insects such as mantises, beetles, crickets, and grasshoppers for survival and reproduction. This parasitic worm begins its life cycle in bodies of water such as streams, pools, puddles, and ponds. It reaches dry land by sticking to aquatic insects such as mayflies. At this point, it waits to be consumed by its host to get to work finally.

Once inside the guts of its host, the horsehair worm begins to grow rapidly and manipulate the insect. When it fully matures, it compels the host to jump in the water and drown themselves, completing its life cycle.

This mind-controlling ability of horsehair worms is achieved using biochemical signals that mimic the host's central nervous system. However, the mechanism by which these molecules are created has been a mystery for some time.

Gene-Snatching Scheme

Researchers from the RIKEN Center for Biosystems Dynamics Research in Japan performed a genetic analysis of the horsehair worms to investigate how this molecular mimicry is achieved. Led by Tappei Mishina, the team studied the whole-body gene expression of the parasite before, during, and after infecting a mantis.

It was found that during the manipulation scheme, 4,500 of the parasite's genes changed their expressions, while those of the mantis remained the same. This suggests that the worms use the genes to make their proteins. The experts examined these genes in a database and discovered that 1,400 C. horsehair worm genes closely matched those that belong to the mantis whose nervous systems are controlled. Such genes are missing from other species of horsehair worms, which do not use praying mantises as hosts.

In other words, many horsehair worm genes involved in host manipulation are similar to mantid genes. According to Mishina, this suggests that they are acquired through horizontal gene transfer.

The researchers also theorize that the 'mimicry genes' were likely acquired throughout multiple transfer events. The genes that affect circadian rhythms, attraction to light, and neuromodulation are also particularly useful for controlling the host.

By studying the parasitic worms, Mishina and other scientists gained insight into multi-cellular horizontal gene transfer and the inner workings of this non-sexual piece of evolution. Additionally, it also helped experts understand how bacteria gain resistance to most of our advanced medicines.

What is Horizontal Gene Transfer?

Horizontal gene transfer refers to the movement of genetic materials between organisms other than the vertical transmission from parents to offspring. Also known as lateral gene transfer, it involves the non-sexual activity of genetic information between genomes.

It was previously thought that horizontal gene transfer is a rare process only in bacteria. Recently, scientists found it also occurs in wild plants, plant parasites, and even between frogs and snakes through shared parasites like leeches.

In this process, new genes or functions are snatched to enable the organisms to adapt more quickly than they could through mutation alone. It is also the primary way in which bacteria develop antibiotic resistance.