Abstract
During early spermiogenesis in the tick Dermacentor andersoni, Golgi complex derived, multiple cisternae become situated beneath the plasma membrane of early spermatids. Such cisternae eventually elongate and fuse, resulting in a single cisternum per spermatid. Cytoplasmic processes extend from the inside wall of the cisternum and become aggregated at one end of the cisternum, which begins to elongate and is in fact the presumptive anterior end of mature spermatozoa. In this region of cellular process aggregation the cytoplasm begins to protrude as an elongate, rod-shaped structure into the elongating cisternal cavity. As it does, it carries with it the cellular processes along its outside surface. The elongating portion of the spermatid eventually ruptures through the cisternal wall and elongates into a 500–600 μm long, mature spermatozoon. The spermatozoon cytoplasm is characterized by large numbers of centrally located glycogen granules and a subplasmalemmal, fibrillar-granular-like region, but lacks microtubules at any stage of development. Cellular processes extend from the anterior end of the sperm and are situated along its outer surface throughout its entire length. Based upon electron density, morphology, and location within the cellular processes, three different components of the processes are described. The significance of the absence of microtubules from both elongating spermatids and mature spermatozoa and the unusual fine structure of the cellular processes are discussed. It is concluded that spermatid elongation and motility in these spermatozoa are independent of microtubules. Motility may reside in some component of either the fibrillar-granular-like region, the cellular processes, or both.
Published Version
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