|Description:||Magnified 128X, this photomicrograph revealed some of the ultrastructural features displayed by a fertilized, decorticated Ascaris lumbricoides egg. A. lumbricoides is the largest nematode (roundworm) parasitizing the human intestine.|
Fertilized and unfertilized A. lumbricoides eggs are passed in the stool of the infected host. Fertilized eggs are are rounded and have a thick shell with an external mammillated layer that is often stained brown by bile. In some cases, the outer layer is absent (known as decorticated eggs). Fertile eggs range from 45Ám to 75Ám in length. Unfertilized eggs are elongated and larger than fertile eggs (up to 90Ám in length). Their shell is thinner and their mammillated layer is more variable, either with large protuberances or practically none. Unfertile eggs contain mainly a mass of refractile granules.