ENZYMATIC AND ULTRASTRUCTURAL-CHANGES IN THORACIC MUSCLES OF TRIATOMINE INSECTS DURING THE LAST STAGES OF METAMORPHOSIS

Dipetalogaster maximus and Triatoma infestans are hematophagous insect s, vectors of Chagas' disease. After the last molt of their metamorpho sis, from fifth instar nymph to adult, they acquire wings and the abil ity to fly, which is important for their dispersal. Some biochemical c hanges accompanying this last stage have been studied by determining a ctivity of hexokinase (EC 2.7.1.1), fructose-6-phosphate kinase (EC 2. 7.1.11), glucose-6-phosphate dehydrogenase (EC 1.1.1.49), glutamate de hydrogenase (EC 1.4.1.4), aspartate aminotransferase (EC 2.6.1.1), mal ate dehydrogenase (EC 1.1.1.37) and glycerol-3-phosphate dehydrogenase (EC 1.1.1.8) in thoracic muscle extracts of fifth instar nymphs and a dults. Activity of all the enzymes, expressed in U per mg protein, was significantly higher in muscles of adults than of nymphs, except that of aspartate aminotransferase, had lower activity in. adults of T. in festans. The increase of glycerol-3-phosphate dehydrogenase activity w as particularly striking (30-fold), while the increase in glucose-6-ph osphate dehydrogenase activity was of a lesser magnitude than those ob served for other enzymes. Comparative ultrastructural studies of thora cic muscles showed that in adult preparations mitochondria were more n umerous and larger in size, and presented more cristae than in muscles of fifth instar nymphs. The biochemical changes detected appear to be the expression of the adaptation of adult muscles for flight activity . Thus, adult muscles would have higher glycolytic and respiratory cap acity than those of fifth instar nymphs. The operation of systems tran sferring hydrogen into mitochondria, especially that of the glyceropho sphate shuttle, may be greatly increased in adult muscles. Copyright ( C) 1996 Elsevier Science Inc.