Sunday, 23 November 2014

Ampulex compressa: The Wasp That Turns Cockroaches Into Zombies

Jewel wasp, the wasp that mind controls cockroaches
Jewel Wasp
By Muhammad Mahdi Karim (Own work) [GFDL 1.2],
via Wikimedia Commons
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Suborder: Apocrita
Superfamily: Apoidea
Family: Ampulicidae
Genus: Ampulex
Species: Ampulex compressa
Common Name(s): Emerald cockroach wasp or jewel wasp

The Emerald cockroach wasp is best known for its unusual parasitoid reproductive behavior, which among other includes stinging and injecting a cockroach with mind controlling toxins and using its live body as a host for its larvae.

While a number of venomous wasps and other organisms paralyze prey as live food for their young, the Jewel wasp is different in that it initially leaves the roach mobile and modifies its behavior in a truly unique way.

But let's take everything from the start.

It was back in 1940s when researchers first noticed that female jewel wasps sting the Australian cockroach (Periplaneta australasiae) twice, first on the thorax and then on the head. In 2003, a study using radioactive labeling revealed that the wasp stings precisely into specific ganglia of the cockroach.

The first sting is delivered to the prothoracic ganglion. The injected venom mildly and reversibly paralyzes the front legs of the victim, inducing temporal and partial loss of mobility for the next 2-3 minutes.

When the roach is paralyzed and less dangerous, comes a second, more precise sting, this time right into the victim's brain, to the sub-esophageal ganglion which controls walking, the escape reflex and other mobility-related functions. As a result of the second sting, the cockroach begins to groom extensively, becomes sluggish and fails to show normal escape responses.

Jewel wasp stings cockroach in the head to start the parasitic cycle
Jewel Wasp stinging a cockroach in the head.
Credit: Ram Gal & Frederic Libersat 

The venom doesn’t actually affect the general motor skills of the roach. It can still run away, but it "thinks" that there's no reason to do so as the venom apparently inhibits the desire to move around, flee from potential danger and even react to pain. The cockroach is essentially now in a zombified state with no free will.

The wasp then proceeds by chewing off half of the victims antennae, most probably to replenish fluids by drinking the hemolymph, the insect version of blood that’s packed with sugars and proteins.

The wasp, which is too small to carry the roach, then leads the victim to the wasp's burrow, by pulling it from one of the two antennae, much like a dog on a leash. Once there, the wasp lays a white egg, about 2 mm long, on the roach's abdomen. The wasp exits the burrow and proceeds to block the entrance with pebbles, more to keep other predators out than to keep the cockroach in.

With the escape reflex disabled, the now zombified cockroach simply rests in the burrow. After 3 days the fun begins. The egg hatches and the larva feeds for the next 4–5 days from the cockroach's tissue. Then it chews its way inside the abdomen and proceeds to live as an endoparasitoid in the still alive cockroach.

Over the next 8 days, the wasp larva consumes the roach's internal organs in an order that maximizes the likelihood that the roach will stay alive, at least until the larva enters the pupal stage and forms a cocoon inside the host's body. Eventually, the fully grown wasp will emerge from the roach's body, much like an alien chestburster, and begin its adult life.

Related Facts
- It takes about 15 seconds for the wasp to locate and sting the head in the correct spot
- Studies have shown the wasp actively searches for the sub-esophageal ganglion during the second sting. When researchers removed the part of the cockroach’s brain that the wasp normally stings they found out that the wasp will continue stinging the cockroach for up to 3 minutes in various spots, trying to find it. However, if the sub-esophageal ganglia is spared but the nerve is cut, the wasp is fooled and stings like it normally does.
- Researchers have developed an antidote for the venom, which allows the cockroach to exhibit more normal behavior after being stung. Furthermore, they also have found that if other areas of the cockroach’s brain are administered with the venom, even areas close to the the sub-esophageal ganglia, there is no major effect on the behavioral patterns of the cockroach.

You may also like
Video on the topic by History Channel

References & Further Reading
- Williams, F. X. (1942) "Ampulex compressa (Fabr.), a cockroach-hunting wasp introduced from New Caledonia into Hawaii". Proc. Hawaiian Entomological Society, 11:221–233.
- Haspel, G., Rosenberg, L., & Libersat, F. (2003). Direct injection of venom by a predatory wasp into cockroach brain Journal of Neurobiology, 56 (3), 287-292 DOI: 10.1002/neu.10238
- Moore EL, Haspel G, Libersat F, & Adams ME (2006). Parasitoid wasp sting: a cocktail of GABA, taurine, and beta-alanine opens chloride channels for central synaptic block and transient paralysis of a cockroach host. Journal of neurobiology, 66 (8), 811-20 PMID: 16673394
- Gal, R., & Libersat, F. (2010). A Wasp Manipulates Neuronal Activity in the Sub-Esophageal Ganglion to Decrease the Drive for Walking in Its Cockroach Prey PLoS ONE, 5 (4) DOI: 10.1371/journal.pone.0010019
- Banks, C., & Adams, M. (2012). Biogenic amines in the nervous system of the cockroach, Periplaneta americana following envenomation by the jewel wasp, Ampulex compressa Toxicon, 59 (2), 320-328 DOI: 10.1016/j.toxicon.2011.10.011

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