WHITE PUPA - A CERATITIS-CAPITATA MUTANT LACKING CATECHOLAMINES FOR TANNING THE PUPARIUM

The white pupa mutant of the Mediterranean fruit fly, Cevatitis capita ta, fails to tan the puparium, but develops normal larval and adult cu ticular structures, We found that the puparium of this mutant underwen t minor stiffening at the beginning of pupariation, but subsequently d id not increase further in stiffness, By the end of puparium formation , it was fivefold less resistant to compression than the wild type str ain, Scanning electron microscopy of cross-sections of puparial exuvia e revealed a dense sclerotized cuticle in the wild type, whereas the w hite pupa cuticle was quite distinct, with the inner two-thirds consis ting of unsclerotized lamellae and the outer third being a dense, nonl aminar, amorphous layer, Puparial catecholamine levels were also very low in the white pupa when compared with the wild type strain, in whic h N-beta-alanyldopamine (NBAD) predominated, However, in mutant hemoly mph, NBAD, N-acetyldopamine (NADA), and dopamine were about 10 times m ore concentrated than in the normal phenotype, By injecting 1-C-14-bet a-alanine as a tracer, we confirmed that N-beta-alanyldopamine incorpo ration into the puparium was much lower in the white pupa than in the wild type strain, However, insoluble cuticle phenoloxidase activity wa s similar in the two strains, Tanning occurred in vitro when white pup a puparial cuticle, free of epidermis, was incubated with either NBAD or NADA, and melanization occurred when the cuticle was incubated with dopamine, demonstrating that tanning enzymes, but not substrates, wer e present in white pupa puparial cuticle, Solid state C-13 nuclear mag netic resonance spectroscopy revealed that more chitin as well as less protein, catechols and p-alanine were present in the white pupa cutic le relative to the wild type, We conclude that the white pupa mutant i s defective in the mechanism that provides hemolymph catecholamines to the puparial cuticle; this defect prevents normal sclerotization and pigmentation.