Production of insect juvenile hormone by the microsporidian parasite Nosema

Abstract

WHEN microsporidian parasites of the genus Nosema infect insects, abnormal growth and metamorphosis are commonly observed. Heavily infected pupæ of saturniid Lepidoptera moult to adults which retain many pupal characters 1. When flour beetles of the genus Tribolium are similarly infected, they appear larger than normal and die at or before pupation2. We have found that the larger size of such infected beetle larvæ is a result of more rapid growth and of supernumerary moults. All these effects resemble those which can be produced by injection of insect juvenile hormone or by implantation of corpora allata, the endocrine gland which produces this hormone3-6. Three hypotheses could explain this similarity of parasitic infection and endocrine activity: (1) The parasite might cause hypertrophy of, or hypersecretion by, the corpora allata of the host. (2) The parasite might cause other tissues of the host to produce juvenile hormone. (3) The parasites, themselves, might produce materials with juvenile hormone activity. We have carried out experiments by which we can decide among these alternatives. © 1962 Nature Publishing Group.