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Frédéric Libersat "Wasps Injects Cocktail of Neurotoxins in The Brain of Its Prey to Manipulate Motor Behaviors."

Abstract :


Venomous predators use neurotoxins that generally act at the neuromuscular junction, resulting in different types of prey paralysis.
Parasitoid wasps incapacitate their prey to provide a food supply for their offspring. Because the wasp’s goal is to provide a living meal for its newborn larva, the behavioral and metabolic changes in the host are brought about by manipulating the host behavior and metabolism in a way beneficial to the wasp and its offspring. To this end, these wasps have evolved venom-coktails and methods of venom delivery tailored to the wasp hunting and its larva feeding strategies. The sting of the parasitoid wasp Ampulex compressa is unusual, as it induces grooming behavior, followed by a long-term lethargic state of its insect prey, thus ultimately providing a living meal for the newborn wasp larvae. These behavioral modifications are induced only when a sting is inflicted into the head. These unique effects of the wasp venom on prey behavior suggest that the venom targets the insect’s central nervous system. The mechanism by which behavior-modifying compounds in the venom transverse the blood-brain barrier to induce these central and long-lasting effects has been the subject of debate. We demonstrate that the wasp stings directly into the target ganglia in the head of its prey. To prove this, we produced “hot” wasps by injecting them with C14 radiolabeled amino acids and used a combination of liquid scintillation and light microscopy autoradiography to trace radiolabeled venom in the prey. To our knowledge, this is the first direct evidence documenting targeted delivery of venom by a predator into the brain of its prey.
To investigate what guides the sting, we first introduced the wasp to roaches whose brains had been removed. Normally, it takes about a minute for the wasp to find its target, sting, and fly off.
But in the brainless roaches, the wasps searched the empty head cavity for an average 10 minutes. A radioactive tracer injected into the wasps revealed that when they finally did sting, they used about 1/6 the usual amount of venom. When we took a closer look at the wasp's stinger with an electron microscope, we found tiny structures near the tip that resemble sensory receptors found in other insects. The two consecutive stings of the parasitoid wasp Ampulex compressa are unusual, as they induce a transient paralysis of the front legs followed by grooming behavior and then by a long-term hypokinesia of the cockroach prey. The first sting in the thoracic central nervous system causes a transient front leg paralysis lasting a few minutes. This paralysis is due to the presence of a venom component that induces a postsynaptic block of central cholinergic synaptic transmission. Dopamine identified in the venom appears to induce 30 minutes of intense grooming. During the long-term hypokinesia that follows the grooming, specific behaviors of the prey are inhibited while others are unaffected and the overall metabolic rate of the cockroach is modulated. We have recently found that the spontaneous activity of thoracic octopaminergic neurons, which is modulated by descending input, are depressed in stung cockroaches The alteration in the activity of octopamine neurons could be part of the mechanism by which the wasp induces a change in the behavioral state of its prey and also affects its metabolism.

Selected publications

Rosenberg LA, Pflüger HJ, Wegener G and Libersat F Venom of wasp injected into the prey’s brain modulates thoracic identified bioaminergic neurons.
J. Neurobiol. 2006. 66(2):155-68.
Haspel G , Rosenberg, L.A. and Libersat F
Direct injection of venom by a predatory wasp into cockroach brain.
J Neurobiol. 2003. 56:287-92.
Haspel G and Libersat F
Wasp venom blocks central cholinergic synapses
to induce transient paralysis in cockroach prey.
J. Neurobiol. 2003. 54:628-637.
Reviews
Libersat F and Pflueger HJ
Monoamines and the orchestration of behavior. Bioscience, 2004. 54 (1) 17-25
Libersat F
Wasp uses venom cocktail to manipulate the behavior of its cockroach prey.
J Comp Physiol [A] 2003. 189:497-508.
Web Link of interest
News at Nature.com:
http://www.labanimal.com/
news/1999/990401/pf/990401-4_pf.html
Science now, 10/14/2004:
http://sciencenow.sciencemag.org/cgi/
content/full/2004/812/3
Corante:
http://loom.corante.com/archives/
2006/02/02/the_wisdom_of_parasites.php

Bernard Bioulac