Growth and development of flight muscle in the locust (Schistocerca nitens, Thünberg)

Abstract

AbstractThe isometric contraction kinetics, ultrastructure, and growth of locust flight muscle that is derived from body wall muscle (metathoracic dorsal longitudinal muscle) and from limb muscle (second metathoracic tergocoxal muscle) were studied during the last three nymphal instars and in the adult 2 weeks past the terminal molt. Two distinct developmental patterns were found that correlated with use during nymphal life. The second tergocoxal muscle (TC2) is used from the time of hatching as a coxal remoter. As such, its contraction kinetics and ultrastructure are characteristic of fast, phasic muscle, which predisposes it to use in the adult as a wing levator. In contrast, the dorsal longitudinal muscle (DLM) is nonfunctional during nymphal life; contraction kinetics and ultrastructure characteristic of fast, phasic muscle develop gradually in late nymphal life until the adult kinetics are attained 2 weeks past the terminal molt. Although growth in both of these muscles occurs as the result of increases in fiber number and cross‐sectional area, there are differences in the manner in which this growth is achieved. In the TC2, there is a continuous increase in fiber number through the last three nymphal instars. In contrast, in the DLM, the increase in fiber number is nearly complete by two molts before adulthood.