Differential basic nucleoprotein kinetics in the two kinds of lepidoptera spermatids: Nucleate (eupyrene) and anucleate (apyrene)

Normal lepidopteran males produce two kinds of spermatozoa: nucleate (eupyrene) and anucleate (apyrene). Eupyrene spermatozoa have the usual type of elongate nuclei. But in apyrene spermatids, the nuclei never elongate and the chromatin remains in a telophase-like condition until enucleation occurs. The study of the differential nucleoprotein kinetics of the two types of spermatids, using the fluorescent dye sulfoflavine, shows that: (1) In the elongate eupyrene nuclei, lysine-rich nucleoproteins are replaced by arginine-rich ones, while in the non-elongating apyrene nuclei only lysine-rich nucleoproteins are detected. However, nuclear elongation is not causally related to nucleoprotein transitions as transitions occur in the eupyrene spermatids after nuclear elongation. (2) The replacement of the nucleoproteins occurs in the eupyrene nuclei in a polarized manner. This may be correlated with the heterogeneous ultrastructural configuration of the chromatin fibers in elongating spermatid nuclei, as shown in other insect species. (3) Concomitantly with the eupyrene spermatid nucleoprotein transition, the cytoplasm of the head cyst cell shows an increasing amount of cytoplasmic lysine-rich proteins, while no such a phenomenon occurs in apyrene cysts. This differential pattern distribution may reflact functional differences among the two types of cysts and is probably related to the regulation of the dichotomy in lepidopteran spermatogenesis.