"Zombie shrimp": How parasites hack host genes to do their bidding
The animal kingdom is home to all kinds of stories – adventures, romance, tragedy, and as it turns out, even horror stories. Scientists at Brown University have now uncovered a creepy new zombie story involving worms that propagate by hack their shrimp host's genome to take control of their minds.
If you watched the HBO series The Last of Us or played the games it was based on, you’ll be familiar with cordyceps. This fungus reproduces by infecting ants and controlling their nervous system like a puppet, forcing them to climb to a high vantage point and clamp down on a leaf, where they can sprout spores to infect more ants. Parasitic wasps have also been found to “zombify” spiders, forcing them to build a special type of web cocoon for their larvae – which then go on to eat said spider.
And then there’s the complex life cycle of a parasite called Levinseniella byrdi, which can only reproduce in the guts of certain marsh bird species. But this little worm likes to travel in its youth before it settles down and starts a family. First its eggs pass into the environment through the bird’s droppings, where they’re eaten by marine snails grazing. The larvae develop and then burrow out of the snail, swimming around the water column until they enter the gills of an innocuous little crustacean known as an amphipod. And that’s where things get weird.
Amphipods are usually pretty shy critters, hiding under vegetation with the help of their dull gray or brown coloring. But once infected by L. byrdi, they change colors and become bright orange, as well as more adventurous, preferring to hang out in the open. Together, those two new traits make them more easily picked off by predatory birds – exactly the kind that the worm needs to get off. And so the cycle continues.
In the new study, the researchers at Brown University investigated how the parasite makes these changes in the amphipod’s biology. They used RNA sequencing to identify genes in the amphipod genome that correspond to the main changes, and found that the worms activate genes that involve pigmentation, interfere with their ability to detect external stimuli, and suppress multiple genes involved in immune responses, which would otherwise fight off the parasite.
While it’s a fascinating story in its own right, the team says that understanding these systems better could eventually help us fight off pathogens that affect humans.
“Characterizing the molecular mechanisms of manipulation is important to advancing understanding of host–parasite coevolution,” said David Rand, an author of the study. Learning the molecular mechanisms of these kinds of host-parasite interactions can have important implications for how to manage pathogens generally, and in humans.”
The research was published in the journal Molecular Ecology.
Source: Brown University