Early suppression of immune response in Heliothis virescens larvae by the endophagous

Abstract

Toxoneuron nigriceps is an endophagous parasitoid of larval stages of the noctuid moth Heliothisvirescens. As all parasitoids, this wasp avoid host immune reaction by a combination of several passiveand active mechanisms. Secretions injected by ovipositing females, which contain venom, calyx fluid andpolydnaviruses, are the most probably factors actively disrupting Heliothis virescens immune system. Thispaper describes the main alterations of the host immune response observed shortly after oviposition by T.nigriceps. A transient block of prophenoloxidase activity is registered along with changes in hemocytenumber, adhesion and structure, which suggest the occurrence of apoptosis. In contrast, the hostplasmatocytes appear structurally unaltered, but unable to produce a capsule in vitro.

Keywords

• insects
• parasitoid
• immune defenses