NOSEMA AS A SOURCE OF JUVENILE HORMONE IN PARASITIZED INSECTS

Abstract

Tribolium larvae infected with nosema pass through as many as 6 supernumary molts, resulting in giant larvae which weigh twice as much as uninfected controls. Growth is stimulated by the presence of the parasite but development to the adult state is inhibited. Infected Tribolium seldom pupate and die as giant larvae. Surgical transplants of nosema to allatectomized Blattaria prevent adult development and a nymph is produced at the next molt. The same effect is obtained if the parasites are transplanted to: (1) the hemocoel, (2) a small glass chamber affixed to the pronotum, but open to the hemocoel or (3) the chamber separated from the hemocoel by a "Millipore" filter with pore diameters too small to permit migration of the parasites. Extracts of parasite spores possess juvenile hormone activity when assayed on Hyalophora acropia pupae and allatectomized Blaberus craniifer. The extracted material does not have sufficient farnesol isomers to explain the juvenilizing effect.