A Study on The Changes During The Maturation of The Late Spermatid and The Structure of The Spermatozoon of Sebastiscus marmoratus

The late spermatid of ovoviviparous teleost,Sebastiscus marmoratus (Cuvier et Valenciennes) possessed the approximate morphology of mature spermatozoon.The dorsal side of the nucleus was flat wheras its ventral side protruded outwards slightly.The chromatin condensed into wads.At its ventral part and posterior end,the chromatin was more compacted.The centriolar complex consisted of proximal centriole and basal body.The proximal centriole was perpendicular to the basal body,thus,the complex was L-shaped.A centriolar adjunct stretched out of the proximal centriole and pointed towards the dorsal side of the nucleus.The centriolar adjunct was composed of 9 microtubules.They formed cylinder-shape as the axoneme.During the process of transforming into spermatozoon,the centriolar adjunct and proximal centriole shrank back in succession,and finally disappeared completely.At the same time,the changes of the shape of the posterior end of the nucleus took place.The disappearing of the centriolar adjunct and proximal centriole in succession might be considered as a sign of being mature completely of the spermatid.The centriolar complex of the spermatozoon consisted of basal body and basal body cap which was between the basal body and the nuclear membrane.The sleeve was connected to the posterior end of the nucleus.There were about 30-40 mitochondria in the sleeve.The flagellum stretched out of the central space of the sleeve.The central structure of the flagellum was axoneme.There was one lateral fin at each side of the axoneme.At the proximal piece of the flagellum the lateral fins beside the axoneme were broad and asymmetrical.