This photomicrograph revealed some of the ultrastructural morphology exhibited by an adult cestode, Echinococcus granulosus, which had been found in a dog. E. granulosus causes what is known as cystic echinococcosis. As dogs and other canids are the only definitive hosts for Echinococcus, adults are not expected to be found in the human host. Adults range from 3mm - 6mm in length and usually consist of a scolex, and three proglottids. The third (terminal) proglottid is gravid, and is longer than wide, as can be seen in this instance. The scolex contains four suckers and a rostellum with 25 - 50 hooks.