Emerald Cockroach Wasp - Biomechanics

Biomechanics

The first sting is delivered to the prothoracic ganglion (mass of nerve tissue) which causes 2-3 minute paralysis of the front legs. This sting injects significant quantities of gamma amino-butyric acid (GABA) and complementary agonists taurine and beta-alanine. The concoction temporarily blocks the motor action potentials in the prothoracic ganglion by depressing cholinergic transmission through the increased chloride conductance across nerve synapses. Individually, all of these substances induce short-term paralysis of the cockroach. When they are injected together in a ratio of 1:0.7:0.4, the effect was longer lasting. GABA activates liquid-gated chloride channels by binding to GABA receptors. Taurine and beta-alanine likely extend the duration of the paralytic affect by slowing the uptake of GABA by the synaptic cleft. Combined, this cocktail of compounds prevents the cockroach from moving and defending itself while the wasp administers the second sting/series of stings.

The second sting turns the cockroach into a zombie of sorts, or a dog on a leash. This sting is administered to the sub-esophageal ganglion (SEG) and is much more precise, hence the need for paralysis and is significantly longer. Studies have shown the wasp actively searches for the SEG during this sting. The second sting inhibits the cockroach’s ability to walk spontaneously, or of its own will, however cockroaches CAN right themselves and swim while under the influence and when startled, will jump but not run. It also causes excessive grooming and alterations in the metabolism of the cockroach. Scientists suspect the metabolic change preserves nutrients for the wasp larva. Researchers have simulated this zombie state by injecting procaine into the SEG. They also determined using extracellular bipolar electrode that neuronal activity was less in stung cockroaches. Research suggests that the venom disturbs the octopaminergic modulation in structures within the roach’s ganglion. Basically, it limits the effectiveness of octopamine, the neurotransmitter that controls muscle contraction in sudden movements.