Sporadic appearance of histones, histone‐like proteins, and protamines in sperm chromatin of bony fish

Abstract In this work we study the presence and the composition of 24 species of bony fish, representing 18 families and 7 orders of teleosts. The species studied belonging to orders Clupeiformes and Lophiiformes display typical protamines, whereas the species belonging to orders Notacanthi‐formes, Gadiformes, and Ophiidiformes contain histones instead of protamines in their sperm nuclei. In these species, one or more specific proteins are added to the pattern of canonical histones and, in the cases that have been analysed compositionally ( Merluccius capensis, Cataetyx laticeps ), the specific proteins seem to be related to histones. Among the order Scorpaeniformes, the species Helicolenus dactylopterus (family Scorpaenidae) presents protamines, whereas Trigla lucerna (family Triglidae) contains histones. Similarly, among the order Perciformes, the species from six families (Percichthyidae, Labridae, Trachinidae, Uranoscopidae, Gempylidae, and Scombridae) have protamines in sperm nuclei and species from two families (Sparidae and Trichiuridae) retain histones and increase the proportion of H1 histone approximately twofold. Two species of Mullus (family Mullidae, order Perciformes) display special proteins with an electrophoretic behaviour corresponding to histone H4 but an amino acid composition more basic. The results indicate that bony fishes have adopted three main alternatives to condense their nuclear sperm chromatin: namely, protamines, histones, and histone‐like proteins. Moreover, these alternatives do not correspond strictly with phylogeny, favouring the hypothesis that the change “protamine → histone” (or alternatively “histone → protamine”) has occurred independently several times during the evolution of bony fishes. © 1993 Wiley‐Liss, Inc.