The architecture of the accessory reproductive glands of the male desert locust: III. Components of the muscular wall.

An electron microscopic study of the sheath enclosing the accessory reproductive glands of the male desert locust has shown that it consists, for the most part, of a single myofibril, and that other tissues (nerve fibres, tracheal elements, and the fat body) are also associated with it to a greater or lesser extent. The myofibril has special features associated with the Z-bands, including the regular infolding and the attachment of the sarcolemma at the Z-bands, and the synapsing of nerve axons at these infoldings, which perhaps facilitate the rapid transmission of nerve impulses into the myofibril. The distribution of the T-systems and sarcoplasmic reticulum (SR) is described, and their relationship to the speed of action of the myofibril is discussed. The myofibril exhibits three distinct bands: the A-, I-, and Z-bands. In the A-band, each thick myofilament is surrounded by 10 to 12 thin filaments. This finding is related to similar findings in other arthropod visceral and slow-acting skeletal muscles. The basement membrane surrounding the glandular epithelium comprises two parts: the inner part, which is structureless and contains neutral mucopolysaccharide; and the outer part which contains numerous collagen-like fibrils and stains for acid mucopolysaccharide. This characteristic is considered in relation to the insertion and function of the myofibril.