DEFENSE AND MELANIZATION DEPEND ON THE EUMELANIN PATHWAY, OCCUR INDEPENDENTLY AND ARE CONTROLLED DIFFERENTIALLY IN DEVELOPING CERATITIS-CAPITATA

A defense mechanism in the hemocytes and cuticle of developing Ceratit is capitata has been demonstrated (Marmaras and Charalambidis, 1992; M armaras et al., 1993a; Marmaras et al., 1993b). To elucidate further t he mechanism and the regulation: of defense reactions, we studied this process in relation to melanization in the major larval tissues, in t wo distinct developmental stages; the feeding and wandering larval sta ges. The results demonstrate that defense reaction depends on reactive tyrosine derivatives of either early or late stages of the sequence o f reactions involved in eumelanin biosynthesis. However, defense and m elanization occur independently e.g. hemocytes exhibit a high degree o f Escherichia coli immobilization and entrapment, but not any ability to biosynthesize melanin. Serum on the other hand, showed a high degre e of melanin formation in wandering stage larvae, but had not any abil ity for E. coli immobilization. In integuments of wandering stage larv ae, both processes occur simultaneously. These findings suggest indepe ndent control mechanisms for these processes. Indeed, our results sugg est that defense seems to be controlled by the presence of proteins re sponsible for nonself recognition and melanization by developmental re gulation of dopachrome conversion factor.