Human sperm diluted in buffer imaged at room temperature within two hours of ejaculation. Cell at center swims at constant speed.

This electron micrograph shows a cross section through the midpiece of opossum sperm. Filamentous cytoplasm underlies a scalloped membrane with regular variations in thickness, which gives it a corrug...

The midpiece of spermatzoa in nearly all vertebrates is enclosed in a sheath of mitochondria, which provide a ready source of ATP necessary for sperm motility. Here, a longitudinal section through sp...

The sequences in this videotape illustrate the unusual crawling motility of the amoeboid sperm of the nematode parasite, Ascaris suum, an intestinal parasite of pigs. Ascaris sperm contain no myosins ...