CHROMOSOMAL-PROTEINS OF THE SPERM OF A CEPHALOCHORDATE (BRANCHIOSTOMA-FLORIDAE) AND AN AGNATHAN (PETROMYZON-MARINUS) - COMPOSITIONAL VARIABILITY OF THE NUCLEAR SPERM PROTEINS OF DEUTEROSTOMES

We have isolated and characterized for the first time the chromosomal proteins from the nucleus of the sperm of a lancelet (amphioxus) Branc hiostoma floridae (Hubbs, 1922) (Phylum Chordata: Subphylum Cephalocho rdata) and of a lamprey Petromyzon marinus (Linnaeus, 1758) (Phylum Ch ordata: Subphylum Vertebrata: Class Agnatha). In the first case, the m ajor protein component of the sperm-chromatin of a lancelet is a highl y specialized protamine-like (PL) protein that has structural and comp ositional features similar to those of PL-III from bivalve mollusks. I n contrast, the chromatin of the sperm of the lamprey has a structural arrangement and protein composition (histones) very similar to that f ound in the somatic cells of all eukaryotic organisms. Among the deute rostomes, chromosomal protein variability is considerably greater in r epresentatives of the Phylum Chordata than in echinoderms. The possibl e evolutionary significance of these findings is discussed.