Structure of the Sperm
The spermatozoa in different animal groups display a wide variety of shapes and sizes but all share a. basic morphological plan. The sperm in most animals is devoid of any stored nutrient materials within itself and is capable of performing locomotion in fluid and semifluid media. The size of sperm may be as small as 0.02 mm (crocodile) or as large as 2 mm (Balanoglossus). The shape of the sperm is species specific. Structurally the sperm of different animals consist of a head, a middle piece and a tail. The account of the sperm structure presented here is based on the studies conducted on mammalian species, particularly, human beings.
Figure: Sperm of some chordates. The break in the flagellum of sperm indicates that a long portion is omitted