Plasma-membrane glycoproteins during spermiogenesis and in the spermatozoa of some Orthoptera

Summary Orthoptera spermatids and spermatozoa from two species of Tettigoniidae and from one of Acrididae were analysed by means of the fluorescent lectins, concanavalin A or wheat-germ agglutinin, with the aim of finding -D mannose· -D glucose· N-acetylglucosamine and sialic acid sugar residues in their plasmamembrane glycoproteins. Labelling with lectins shows remarkable changes occurring in the plasma membrane during spermiogenesis. In early spermatids, the whole cell surface is labelled, but in mature spermatids and spermatozoa, a noticeable fluorescence is restricted to the membrane that covers the acrosome. The end piece of the tail of Acrididae spermatids and spermatozoa fluoresces after wheat-germ agglutinin labelling. The intense labelling of acrosomal area is independent of acrosomal size and shape, as shown by the marked differences observed in the acrosomes of Tettigoniidae compared with Acrididae: in the former, the acrosome is a well-developed structure with an arrow-like shape, but in Acrididae, the acrosome resembles a small vesicle in the anterior tip of the cell. The large amount of some sugar residues in the plasma membrane covering the acrosome is discussed in relation to the features observed in other species, and also in connection with the physiology of the male gamete prior or during fertilization.