Protein Synthetic Activities during Spermiogenesis in the Sea Urchin: An high Resolution Autoradiographic Study of

Protein synthetic activity has been studied during spermiogenesis of Paracentrotus lividus by high-resolution autoradiography using 3 H-leucine as a labeled precursor. Under the adopted experimental conditions 3 H-leucine is incorporated during the whole spermiogenesis period. The early spermatid is the most active stage and it shows labeling over the nucleus, the cytosol and the mitochondria. Nuclear 3 H-leucine incorporation progressively decreases as spermiogenesis proceeds. Cytosol labeling shows similar values at early and intermediate spermatid and it undergoes a considerable decreases at late spermatid. Mitochondrial grain density increases from early to intermediate spermatid and it remains almost constant at late spermatid. Our results are compared with the data reported for other animal groups and possible functions of the observed protein synthesis are discussed.