Ultrastructural studies of cytoplasmic droplets of various mammalian spermatozoa(bull, ram, rabbit, rat, and bat) have revealed only numerous membranous vesicles and tubules in their matrix. The simpl icity of the ultrastructure and lack of other organelles and inclusions in the droplet matrix led researchers to doubt suggestions that cytoplasmic droplets contain endogenous substrates for epididymal spermatozoa survival. Recently, however, biochemical and cytochemical analysis of cytoplasmic droplets in spermatozoa of different domestic animals showed a rather high activity of hydrolytic and glycolytic enzymes.In our study of interspecific variation in sperm morphology within the salamander family Plethodontidae, it was observed that spermatozoa of all examined plethodontid species have a characteristic cytoplasmic droplet. Cytoplasmic droplets of 16 species were examined with the light microscope and in addition, Plethodon qlutinosus was examined with the TEM.
