With further development of proglottids, the worm starts producing eggs, which are released with feces into the environment. The necks of the larvae start production of proglottids, and the strobila forms. In the final host the scolices (SKOH-luh-seez, the plural of scolex) of the larvae attach to the intestinal wall.

The larvae enter the final host when it eats the intermediate host. In most species the larvae have a fully developed scolex identical to that of adult tapeworms. In the new location the embryos transform into larvae. In the intestine of the intermediate host, the embryos hatch and, using their hooks, bore through the intestinal wall and into the body cavity or an internal organ. The eggs, each holding an embryo (EHM-bri-yo), pass into the environment with the final host's feces and are eaten by the intermediate host. Tapeworms follow this general scheme as their life cycle. It seems that most tapeworms attach themselves at a certain site of the intestinal wall and stay there for their entire lives. Scientists know little about the behavior of tapeworms in the intestines of their hosts. Humans become infected with pork tapeworm and beef tapeworm when they eat undercooked or raw meat. The fish tapeworm absorbs vitamin B 12, causing the host to be deficient in a vitamin that is essential for the development of red blood cells. People who eat raw fish often carry fish tapeworms. Tapeworms eat by absorbing nutrients from their hosts' intestines. Larvae (LAR-vee) are animals in an early stage that change form before becoming adults. Tapeworm larvae, which live in a host called the intermediate host before moving to the final host, live in various types of tissue, such as liver, lung, muscle, body cavity, brain, and sometimes even the eyes. Most adult tapeworms live in the intestines of the final hosts, but a few species live in the body cavity. Vertebrates (VER-teh-brehts) are animals with a backbone. Tapeworms live in almost all land, sea, and freshwater habitats where vertebrates live. A few species of tapeworms have no proglottids. The gravid proglottids at the end of the worm break off and pass into the environment with the host's feces (FEE-seez). When a new proglottid forms at the neck, already formed proglottids are pushed toward the rear, grow, and eventually contain the reproductive organs.īehind the new proglottids, each strobila contains the following types of proglottids, from front to back: premature proglottids, with the beginnings of reproductive organs mature proglottids, which contain functioning male and female reproductive organs postmature proglottids, which contain developing eggs and gravid (GRA-vuhd) proglottids, which contain ripe eggs. Just behind the neck, the proglottids are short and narrow. Each proglottid starts development at the neck, and proglottids form one by one throughout the life of the tapeworm in the final host. The strobila is made up of anywhere from a few to more than one thousand proglottids but usually contains several dozen. It consists of a row of segments called proglottids (proh-GLAH-tuhds). The neck is the region of the body just behind the scolex. Suckers are usually cup shaped and have powerful muscular walls. Suckers are the most common attachment tool. It has spines, hooks, suckers, tentacles, glands releasing sticky secretions, or a combination of these structures that the worm uses to attach itself to the inner wall of the intestine of the final host, also called the primary host. The body of tapeworms has three regions: scolex (SKOH-leks), neck, and strobila (stroh-BYE-luh). Tapeworms are whitish and as internal parasites they live in darkness. This covering also protects the worms from the host's immune reactions and digestive acids. Tapeworms have a body covering through which they absorb nutrients from the host's intestine. Parasites (PAIR-uh-sites) are animals or plants that live on or in other animals or plants, or hosts, without helping them and usually harming them.

Tapeworms are parasites that have no head, mouth, or digestive system. The length varies from 0.02 inch (0.6 millimeter) to 98 feet (30 meters), the longest worms being found in sperm whales. The body of most tapeworms is flat and much longer than it is wide, so that it looks like a tape or ribbon. TAPEWORMS: Cestoda BROAD FISH TAPEWORM ( Diphyllobothrium latum): SPECIES ACCOUNTS DOG TAPEWORM ( Echinococcus granulosus): SPECIES ACCOUNTS NO COMMON NAME ( Proteocephalus longicollis): SPECIES ACCOUNTS PHYSICAL CHARACTERISTICS

Broad fish tape worm