Morphology of the spermatid and spermatozoon of Amblyomma hebraeum Koch (Acarina; Ixodidae).

Spermatids and spermatozoa of Amblyomma hebraeum were examined by scanning and transmission electron microscopy as well as by freeze-etch and freeze-fracture techniques. The external surface of the spermatid is smooth except for a rim of two parallel grooves near the anterior apex. This rim probably marks the level at which a cap detaches, permitting extrusion of the inner cord during spermatozoon maturation. Both ends of the spermatid are closed, the anterior part being slightly thicker than the posterior. The spermatozoon is clavate anteriorly and tail-like posteriorly. The tip of the anterior part is a hemispherical structures carrying numerous bulbous expansions. Apart from the hemispherical structure, the entire spermatozoon surface is covered with parallel longitudinal cellular processes. Waves of constrictions on the tail-like part of the spermatozoon and undulations of the cellular processes are considered to be involved in sperm motility.