Evidence for Humoral Regulation of Digestive Secreation in the Beetle, Tenebrio Molitor

Abstract

1. Midgut protease values of starved adult Tenebrio injected with the blood of recently fed adults were, on average, higher than those of similar recipients of the blood of starved donors, or of untreated starved adults of the same age. A similar increase was found in the recipients of blood of newly-emerged adults. 2. Protease activity failed to develop in the midguts of adults which had been decapitated one day before emergence. If decapitation occurred after emergence, enzyme activity developed, but at a slower rate and to a lower maximal level than in the normal adult. Inhibition of the development of enzyme activity was greater the sooner decapitation followed emergence. 3. A few experiments suggested that injection of the blood of normal newly emerged adults could to some extent rehabilitate the development of enzyme inhibited by pupal decapitation. 4. These observations are discussed in relation to the hypothesis that digestive secretion may be under humoral regulation.