ACROSOME AND SURFACE-COAT FORMATION IN GRYLLOTALPA-AFRICANA L (ORTHOPTERA, GRYLLIDAE)

Acrosome formation in Gryllotalpa africana begins in young spermatids of the Nebenkern stage where the Golgi apparatus is associated with it s cis-face to the nuclear envelope in a lateroposterior position. By f usion of several small vesicles emerging from the transtubular network a single acrosomal vesicle is formed which almost from the beginning shows specializations of its membrane and differentiation of its conte nts making it possible to recognize the later orientation of the organ elle. A section of the acrosomal membrane, which is accentuated by a t hin layer of electron-dense material attached to its inner face, comes first into contact with the cell membrane. In another part of the mem brane a layer appears on the outer face marking the later place of con tact with the nucleus which is not established before the acrosomal ve sicle has reached the apical pole of the spermatid. While the acrosome begins its further development, contact to the cell membrane is aband oned, a layer of preacrosomal material is seen in the resulting inters pace. At the same time a fuzzy coat appears on the cell membrane, foll owing exactly the extension of the preacrosomal material. Moreover, th is fuzzy coat is always covered by cytoplasm of another cell. In late stages the contact is lost when the fizzy coat is delaminated from the membrane. This lamina surrounds the apical end in loose arrangement b ut tightly covers two lateral bars of electron-dense material extendin g along the whole length of the acrosome. Mature spermatozoa form grou ps of four to five which are held together by membrane contact at thei r tips.