Melanin properties at the different stages towards life cycle of the fly Hermetia illucens

Abstract

Eumelanin type pigments are synthesized at all the stages of the life cycle of the fly Hermetia illucens: in the larvae, pre-pupae, pupae and adult flies (dead flies). The greatest content of melanin was recorded in the cuticles. Melanin was present not only in the cuticle, hence it remained in the cuticle after the emergence of the adult fly. It was also found in the insect body in a complex with lipids. In pupae, it is mostly lauric acid that was associated with melanin. Its proportion in the melanin-chitosan complex was 80%. The isolated melanin-chitosan complex of adult flies showed a wide range of antibacterial activity, inhibiting the growth of 21 out of the 25 of the test cultures. The melanin-chitosan complex of empty pupal membranes and alcohol suspension of pupal melanin inhibited twice as smaller number of test cultures and the above activity was absolutely in the pupal chitosan. The largest zone of growth inhibition was recorded with respect to Aspergillus niger, Candida albicans, salmonella, and Staphylococcus aureus. An alcohol suspension of pupal melanin inhibited the growth of 10 test cultures. In this case the greatest activity was shown in relation to Mycobacterium B5 and Acinetobacter sp. 1182.