A fine-structure study on spermiogenesis in the tick Amblyomma dissimili, with special reference to the development of motile processes

Abstract

Tick spermiogenesis has been studied with the aid of the electron microscope to observe the development of motile processes. During the second maturation division a series of thimble-shaped, subsurface cisternae appear in dividing spermatocytes. Each cisterna encloses a finger-shaped cytoplasmic process. The cisternae are initially equally distributed around the entire surface of the cell but become aggregated at one side as spermiogenesis progresses. During this period the cisternae fuse, resulting in a single cisterna within which multiple cellular processes are now located. The spermatid next elongates into a long, tubule-shaped cell and the intracisternal cellular processes become aggregated at one end of the tube. At this time electron-dense regions appear within each cellular process which eventually give rise to two hollow filaments 60–90 A in diameter and spaced 100–125 A apart. These resulting processes are the motile structures of tick spermatozoids. These findings are compared with the early light microscope investigations on tick spermiogenesis and with other types of motile process fine structure.