ORIENTATION DETERMINATION OF DEVELOPING FLIGHT MUSCLES IN GALLERIA MELLONELLA

Abstract

In the normal development of flight muscles in Galleria, the epidermis, to which the longitudinal muscles attach anteriorly, lies on the anterior side of the myoblasts which form the longitudinal flight muscles. Similarly, the dorsoventral muscle orientating epidermis lies on the dorsal side of the myoblasts from which dorsoventral flight muscles develop. Shifting the dorsoventral muscle orientating epidermis to the dorsal side of myoblasts which normally form longitudinal muscles produces dorsoventrally directed muscles in the normal place of longitudinal muscles. Thus a given group of myoblasts can form longitudinal or dorsoventral muscles under different conditions when the myoblasts are subjected to the influence of dorsoventral or longitudinal muscle orientating epidermis put in a similar topographic relationship with these myoblasts. The myoblasts respond to both kinds of epidermis in the same way: the developing muscles stretch between the muscle orientating epidermis and the myoblasts. Thus, there appears to be no qualitative difference between longitudinal and dorsoventral muscle orientating epidermis with regard to flight muscle orientation. The importance of topographic relationship between myoblasts and the muscle orientating epidermis is stressed as being the causative factor in determining the orientation of developing flight muscles in Galleria.