Spermiogenesis in the Sea Urchins Arbacia lixula and Echinometra locunter (Echinodermata)

Abstract

The spermiogenesis in the sea urchins, Arbacia lixula and Echinometra locunter, has been investigated by means of electron microscopy.
In the gross morphological aspects sperms are similar and show three main parts: the head, the short middle piece and the flagellum.
The nuclei of developing spermatids are irregulary shaped with a less condensed chromatin and a prominent nucleolus. A very dense globular inclusion was a common characteristic of this stage.
Throughout differentiation sperm cells are connected by intercellular bridges. The complete isolation of the four spermatozoa from each spermatocyte results only when there is no more cytoplasm in the cell.