Digger wasp versus cricket: immediate actions of the predator's paralytic venom on the CNS of the prey.

The females of the palaearctic digger wasp species Liris niger hunt crickets (e.g., Acheta domesticus) as food for their future brood. The wasps paralyze the prey by injecting their venom directly into each of the three thoracic ganglia and the suboesophageal ganglion. This study describes the effects produced by the Liris venom at the level of the intact prey animal (by chronic electromyogram) and at the level of a dissected preparation (by extra- and intracellular records) during the immediate action. Natural or artificial injections of the Liris venom into various ganglia revealed that: (a) The venom injection induced an about 15- to 35-s long tonical discharge of the neurons located in the stung ganglion. This discharge is usually accompanied by convulsions of the prey's limbs. (b) Subsequently, the generation and propagation of action potentials are blocked for up to 30 min (total paralysis). (c) During total paralysis, the venom blocks synaptic transmission. (d) The effects of the venom are restricted to the stung ganglion. Responses of mechanoreceptors in the legs can be recorded from the peripheral nerves of the stung ganglion during the whole period of total paralysis. (e) The neurons almost completely recover after this period. The venom does not selectively affect leg motoneurons, but affects any neuron (e.g., internerneurons or neurosecretory neurons) in any part of the central nervous system of the prey where it was released.