Peculiar Features of the sperm of a calanoid copepod Arctodiaptomus salinus

Mature spermatozoa were found within the spermatophore in the seminal vesic le at the end of the deferent duct. The cells measured 2-3 mu m in diameter and were almost spherical; the nucleus was mixed with the cytoplasm as no envelope was present to separate them. They lack flagellum and any acrosome -like structure. The dispersed chromatin forms small granules surrounding t he mitochondria, characterised by a small number of highly modified cristae . Under the plasmatic membrane, a group of electron-dense lamina enclose th e whole cytoplasm. In the final phase of spermiogenesis, the dismantling of the nuclear envelope, the formation of chromatin granules and the modifica tion of mitochondria occur. This process takes place simultaneously with th e synthesis of the components of the spermatophore by the epithelial cells of the deferent duct. All these characteristics of the sperm of A. salinus identify it as being a peculiar case among copepoda. (C) Elsevier, Paris.