Parasitoid wasps take control of spider minds to get them to do their bidding, turning them into obedient zombie workers.
New research takes a closer look at the making of the spider zombies to figure out how the arachnid becomes under the control of certain species of wasps.
In a paper published in the Biological Journal of the Linnean Society, researchers suggest that the "zombification" process involves the wasps hacking into the spider's pre-existing system with injections of the molting hormone known as ecdysone.
Zombifying Spiders
It starts off innocuously enough with the parasitoid wasp laying its eggs on the back of the spider. When the tiny larvae hatch, they latch onto the spider's abdomen.
The larvae remain an external parasite on the surface, but they gain access to the brain by injecting psychotropic substances into the hemolymph, which is a substance in the abdomen of the spider. Then the hemolymph carries the injected substance to the spider's central nervous system.
Once the wasp has hacked into the brain with the substance, the spider becomes compelled to weave a special web with the wasp pupa safely suspended. Its mission complete, the spider goes on to a quick death.
According to the study's co-leader Marcelo Gonzaga of the Universidade Federal de Uberlândia, there have been a number of studies that have suggested the webs that parasitized spiders make for wasps are very similar to the webs unparasitized spiders make before molting. Molting is the process of shedding the exoskeleton.
Another previous study observed that a specific genus of spider was found with unusually high concentrations of ecdysone just after building cocoon webs.
"[We] predicted that the specificity of the wasp larva's effects may already be present in the spider's nervous system, in the form of its specific behavioral responses to the hormone that controls its own molting cycle," explained Gonzaga in a news release from Smithsonian Tropical Research Institute, adding that wasps are able to ensure the safety of the next generation by hacking into the pre-existing system.
Scientists Plan Further Research
With their proposed mechanism in place, study co-leader William Eberhard of the Smithsonian Tropical Research Institute explained that they can observe the details of "zombification" through the lines in cocoon and molting webs.
These two web types vary, but the scientists also discovered that the variations partially overlap.
He added that there's a high probability that larvae change the spider's behavior of constructing molting webs a little for additional protection.
"The mechanisms by which these additional modifications are obtained may result from differences in the timing or amounts of ecdysone, or modifications in the ecdysone molecules themselves, but they remain to be documented," Eberhard concluded.
