Hymenolepis cysticercoid

This differential interference contrast photo clearly illustrates the basic structure of a cysticercoid. On the left side is the main cyst that contains the tapeworm scolex. The cyst wall is multilayered, and the scolex itself is the small, almost circular structure in the middle that has the bright margins. Surrounding it is a thick tissue layer, less bright, with a clear anterior pore leading to the inside. Yet another layer of tissue is faintly visible on the outside.

On the right side is the cercomer, which is a vestigial structure. The cercomer is quite variable in length, even for cysticercoids within the same host, but generally is shorter or even absent in old cysticerocids.