Direct Injection of Venom by a Predatory Wasp into Cockroach Brain

ABSTRACT: In this article, we provide direct ev-idence for injection of venom by a wasp into the central nervous system of its cockroach prey. Venomous pred-ators use neurotoxins that generally act at the neuro-muscular junction, resulting in different types of prey paralysis. 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 com-pounds in the venom transverse the blood-brain barrier to induce these central and long-lasting effects has been the subject of debate. In this article, we demonstrate that the wasp stings directly into the target ganglia in the head of its prey. To prove this assertion, we produced “hot ” wasps by injecting them with 14C radiolabeled amino acids and used a combination of liquid scintilla-tion and light microscopy autoradiography to trace ra-diolabeled 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