Tapeworm metacestode. Scanning electron micrograph (SEM) of the bladder worm or metacestode stage of the dog tapeworm (Taenia hydatigena), an intestinal parasite.Taenia hydatigena is an adult parasite of dogs with the metacestode (Cysticercus tenuicollis) stage residing in ruminants and pigs. The metacestode infection due to C. tenuicollis is important because it causes huge economic losses due to condemnation of infected offal or meat. Magnification: x50 when printed at 10 centimetres high.