Flight muscle development in Locusta migratoria: Effects of implantation of corpora allata on the attainment of metabolic enzyme activities

Abstract

The effects of corpora allata (CA) implantation on the development of the dorsolongitudinal flight muscles and the wings and on the pigmentation in Locusta migratoria were investigated. Fifth-instar female larvae 0–24 hr after ecdysis received either one pair of CA taken from adult females or one, two, three, or four pairs of CA taken from young fourth-instar larvae. Implantation of one, two, or (except for a few cases) three pairs of larval CA did not produce any effect. However, after implantation of four pairs of larval CA, 50% of the insects arising from the subsequent molt displayed predominantly larval characteristics regarding pigmentation and wings. This phenomenon was never observed in the locusts implanted with adult CA, since the ecdysis following the implantation always resulted in the production of individuals with predominantly adult characteristics. Implantation of either adult CA or four pairs of larval CA gave rise to an extra larval stage and consequently an extra (sixth) ecdysis. During this extra larval period, flight muscle development appeared to be retarded in comparison with control insects, as was reflected by lower specific activities of enzymes indicative of aerobic metabolic pathways, such as carbohydrate oxidation and, in particular, fatty acid oxidation. Implantation of larval CA or adult CA resulted in essentially the same pattern of enzyme activities. The activity of lactate dehydrogenase, which in the control insects reached its maximum value around the fifth (imaginal) ecdysis, was in the CA-implanted locusts at its maximum value at the extra (sixth) ecdysis, which may be indicative of the period of invagination of tracheoblasts into the muscle fibers. The correlation between the JH titer and the prevention or inhibition of flight muscle developmental processes is discussed.