One difference between male and female Ascaris, known as intestinal roundworms, is that the females are longer and wider than the males. Ascaris roundworms exhibit sexual dimorphism, meaning each gender possesses distinctly different sexual organs.
Male Ascaris roundworms range from 0.08 to 0.16 inches wide and 0.6 to 1.2 inches long, while females are 0.12 to 0.24 inches wide and 0.8 to 1.9 inches long. Male reproductive organs include a single thread-like testis, a short vas deferens leading into the wide tube of the seminal vesicle, a narrow muscular ejaculatory duct and two penial sacs. The females have two long, thread-like ovaries that take up one-third of their bodies. Thin oviducts open into the wider, thicker tubes of the uteri. The two uteri unite to form a single vaginal opening.
Adult Ascaris roundworms have life spans of 10 months to two years in human small intestines. If humans are infected with males only, no eggs are produced. If only female infestation occurs, eggs are laid but they are infertile and do not become infectious. However, if both males and females are present, they copulate, and the males fertilize the ova. A female uterus holds up to 27 million eggs, and a female may lay up to 200,000 eggs daily.