Phenoloxidase System of the Black Pupae in the Silkworm, Bombyx mori L.

Abstract

In order to explain the controlling mechanism of the black pupae by the hormone determining the black pupal color, the authors investigated the changes in the phenoloxidase activity of the blood and the integument at the time of the manifestation of the black pupae. From the results of these experiments it became clear that there is a close relationship between the phenoloxidase activity of the integument at the end of spinning stage and the formation of black pigment in the cuticle. At least six factors may be considered as predisposing factors for the manifestation of the black pupal color; they are prothoracic hormone, black pupa hormone, black pupa gene (bp), phenoloxidase activity in the blood and the integument, the proenzyme activating substance (activator) and the low temperature incubation at the spinning stage. The details of the interrelationship among these factors are not known but it is plausibly thought that the black pupa gene is either directly or indirectly concerned with the increase of the phenoloxidase activity in the integument after the end of spinning in the presence of the black pupa hormone.