INVITRO RELEASE OF ECDYSTEROIDS BY AN ENDOPARASITOID, ASCOGASTER-RETICULATUS WATANABE

Ascogaster reticulatus larvae removed from their host Adoxophyes sp. and held in vitro released immunoreactive ecdysteroids into Grace's medium. Initially 20-hydroxyecdysone and an unidentified polar ecdysteroid were released, but ecdysone was also present after 24 h incubation. Regardless of the age of the host or size of the parasitoid larva, the maximal release of immunoreactive ecdysteroids occurred when a parasitoid larva developed opaque, fat body spots. We discuss the possibility of direct manipulation of the host haemolymph ecdysteroid titre and subsequent apolysis of the host integument, all initiated by the release of ecdysteroids by the parasitoid larva.