Head - Structure of the Sperm

It exhibits a diversity of shapes in different animal groups, e.g., spherical (teleost fishes), rod or lance shaped (amphibians), spirally twisted like a corkscrew (birds), spoon shaped (man), flattened (buffalo) or hooked (mouse and rat) or occasionally round (bivalve molluscs). Some of these shapes may be interpreted as an adaptation to propulsion in fluid media. The genetic functions are embodied in the nucleus; activation of egg during fertilization is basically initiated by anterior cap like acrosome. The nucleus occupies the greater part of head and it also determines the shape of head. During the course of sperm differentiation (spermiogenesis), everything in the nucleus not directly concerned with the transmission of heredity characters is discarded leaving only the actual material of genes (DNA) which is tightly packed within the nucleus.