The Localization of a Peroxidase Associated With the Formation of Hard Cuticle in Insects

Abstract

Plant peroxidase has been used to trace the uptake of proteins from the blood into multivesicular bodies and storage granules in several insect tissues. Control experiments without plant peroxidase show that an endogenous peroxidase may also be present at some stages, particularly in epidermal cells during the formation of hard brown cuticle. It occurs in granules about 5μ in diameter and is most easily demonstrated in Calliphora epidermis before puparium formation and in the cells forming the proleg spines in Calpodes larvae (Fig. 1). These granules have the structure of MVB's (Fig. 2) and contain acid phosphatase. Since MVB's are usually regarded as organelles for heterolysis, this location for the endogenous enzyme was difficult to reconcile with a functional relation to hard cuticle formation. The paradox was resolved by a study of the proleg spine cells during cuticle formation.