Cockroach Zombie Controlled by Parasitic Wasp
The relationship between the parasitic emerald wasp Ampulex compressa and the household cockroach Periplaneta americana is both complex and macabre. It is a unique relationship as it effects the behavior of the cockroach and manipulates its victim to ensure it can not fight or flee while it is being eaten alive.
The wasp leaves its much larger victim with only the ability to walk and no power over its own movement. It then proceeds to remove the end of its prey’s antennae and ingests the blood to regain the energy lost administering two powerful stings, before attaching itself to the antennae to control the cockroach. This allows to wasp to walk the cockroach straight into the comfort of its nest.
The egg hatches within three or four days and eats internal organs in a specific order that ensures the cockroach will stay alive for a following four days while the larva builds a cocoon. Eventually, the fully-formed wasp emerges from the host’s body and continues the cycle.
The first sting administers large amounts of gamma amino butyric acid (GABA), taurine, and beta alanine into the cockroaches thorax to a mass of nerve tissue to block the transmission of motor signals to temporarily paralyse the cockroaches front legs, preventing the cockroach’s escape and allowing the wasp to administer the second sting. This is a mixture of neurotoxins inflicted directly into the brain of the victim blocking receptors for octopamine, thus preventing complex movements such as walking.
Frederic Libersat and colleagues at Ben Gurion University have shown that stung cockroaches faced with potentially life threatening situations (such as drowning or electrocution) do not flee, but measurement of muscle contractions suggest that they can move. This suggests that although the motor functions remain intact, the will to escape or fight is entirely diminished.
This is an amazing feat of evolution; it has allowed a small parasitic wasp to use a much larger victim as a fresh source of food for its offspring, that otherwise would have been too large for it to transport.