PATTERN SPECIFIC MELANIN SYNTHESIS AND DOPA DECARBOXYLASE ACTIVITY INA BUTTERFLY WING OF PRECIS-COENIA HUBNER

Black pigment extracted from wings of Precis coenia was identified as melanin by solubility characteristics and incorporation of radiolabele d melanin precursors. Different colours in wing scales appeared succes sively, starting with white followed by red, black and grey pigments. At corresponding times [C-14]-tyrosine and [C-14]-3,4-dihydroxyphenyla lanine injected into pupae were incorporated most intensively into bla ck and grey scales. By contrast, red scales were labeled by 3,4-dihydr oxyphenylalanine (DOPA) and, to a lesser extent, by tyrosine when inje cted at the time of red pigment synthesis. Labeled beta-alanine, a com ponent of the sclerotizing agent N-beta-alanyldopamine, was incorporat ed into all scales with the exception of intensely black scales. It is discussed whether the mechanical stability of black scales may be due to melanin itself whereas the stability of all other scales may be du e to N-beta-alanyldopamine. Amounts of extractable melanin increased d uring visible pigment formation in black and grey scales. When [C-14]- tyrosine was offered to isolated wings in Grace's medium before melani zation, 93% of incorporated activity was found in the hydrolysable fra ction and only 7% in the melanin fraction. However, when supplied duri ng intensive melanin synthesis up to 70% was incorporated into melanin . The same incorporation pattern resulted after injection into intact developing pupae. Incorporation of [C-14]-tyrosine into melanin began earlier, and was higher in presumptive black scales than in grey scale s. Incorporation into white scales was always low, DOPA decarboxylase (DDC) activity in whole wings was low during the pupal stage but incre ased at the time when scale melanization started. DDC activity in diff erent coloured wing pieces increased first in presumptive black patter n elements, the eyespots, DDC activity in the eyespots was 3.5 times h igher than in presumptive white parts of the wing; it was intermediate in grey areas. This demonstrates that wing colour pattern as well as colouration intensity are related to selective activity of DDC in time and different locations resulting in different amounts of melanin in grey and black scales.