Fine Structure of Spermiogenesis in the Tick Amblyomma Hebraeum (Acari: Ixodidae): Late Stages of Differentiation and Structure of the Mature Spermatozoon

Spermatids of Amblyomma hebraeum were examined by light and electron microscopy. These large, elongate, tubular cells are pointed at one end and truncate at the other. Each is composed of an outer sheath and an inner cord. The outer sheath lining and the inner cord surface are composed of cellular processes joined at the truncate end of the sperm cell. The nucleus is in the outer sheath. The semispherical apex of the inner cord is covered by numerous bulbous expansions. The final stage of spermiogenesis is the simultaneous evagination of the inner cord at the pointed end and invagination of the outer sheath at the truncate end of the cell. The mature spermatozoon, ca. 200 μm long and consisting of the inner cord added to the former outer sheath, is clavate anteriorly and caudate posteriorly, where the nucleus is located. The mature spermatozoon contains β-glycogen particles and large peripheral granules. A prominent acrosomal complex associated with the nucleus is observed in the aging spermatozoon. The cellular processes and/or the fibrillar granular cytoplasm may have a role in sperm movemen