DIFFERENTIATION OF THE ACROSOMAL COMPLEX IN OSTRICH (STRUTHIO-CAMELUS) SPERMATIDS

The acrosomal complex of ostrich sperm consists of a small, cone-shape d acrosome and a slender, cylindrical perforatorium housed within a de ep endonuclear canal. The perforatorium is almost exclusively endonucl ear in location and is only covered by the acrosome at its point of or igin in the apical subacrosomal space. The development of the acrosome is generally similar to that described in other non-passerine birds. Small proacrosomal granules (vesicles) emanating from the Golgi appara tus coalesce to form a large, membrane-bound acrosomal vesicle filled with homogeneous, electron-dense material. The acrosomal vesicle attac hes to the nucleus via a shallow depression and subsequently collapses to form the typical cap-like acrosome of non-passerine birds. In ostr ich spermatids the endonuclear canal becomes obvious when the collapse d acrosomal vesicle has assumed a dumbbell-shaped appearance. The perf oratorium, which originates from moderately electron-dense material co ntained within the apical subacrosomal space, expands within the deepe ning endonuclear canal. The material of the perforatorium does not ori ginate in the form of an obvious granule as in chicken and budgerigar spermatids. Indications are that in ostrich spermatids the developing acrosome plays a role in the shaping of the tip of the nucleus. The pe rforatorium, however, appears to represent a residual structure that h as no specifically identified function. (C) 1996 Wiley-Liss, Inc.