Trematodes have complex lifecycles that involve a primary host in which sexual reproduction occurs, and one or more secondary hosts in which asexual reproduction occurs. The primary host is almost always a mollusk. Trematodes are responsible for serious human diseases including schistosomiasis, a blood fluke.
The disease infects an estimated million people in the tropics, leading to organ damage and chronic symptoms like fatigue. Infection occurs when the human enters the water and a larva, released from the primary snail host, locates and penetrates the skin.
The parasite infects various organs in the body and feeds on red blood cells before reproducing. Many of the eggs are released in feces and find their way into a waterway, where they are able to reinfect the primary snail host. The cestodes, or tapeworms, are also internal parasites, mainly of vertebrates Figure 3.
Tapeworms live in the intestinal tract of the primary host and remain fixed using a sucker on the anterior end, or scolex, of the tapeworm body. The remaining body of the tapeworm is made up of a long series of units called proglottids, each of which may contain an excretory system with flame cells, but contain reproductive structures, both male and female. Figure 3. Tapeworm Taenia spp. Most reproduction occurs by cross-fertilization.
The proglottid detaches from the body of the worm and is released into the feces of the organism. The eggs are eaten by an intermediate host. The juvenile worm infects the intermediate host and takes up residence, usually in muscle tissue.
When the muscle tissue is eaten by the primary host, the cycle is completed. There are several tapeworm parasites of humans that are transmitted by eating uncooked or poorly cooked pork, beef, and fish. Flatworms are acoelomate, triploblastic animals. They lack circulatory and respiratory systems, and have a rudimentary excretory system. This digestive system is incomplete in most species. There are four traditional classes of flatworms, the largely free-living turbellarians, the ectoparasitic monogeneans, and the endoparasitic trematodes and cestodes.
Trematodes have complex lifecycles involving a molluscan secondary host and a primary host in which sexual reproduction takes place. Cestodes, or tapeworms, infect the digestive systems of primary vertebrate hosts. Improve this page Learn More. Food travels into a gut-type structure that holds and digests it. Once the food is broken down, the digestive system passes it all through the body. Are flatworms dangerous? While New Guinea flatworms pose a potential health threat, they are no more dangerous than the native species of invertebrates that can carry the rat lungworm parasite.
Humans are unlikely to be affected by the rat lungworm parasite since transmission of the parasite can only occur through ingestion. Are flatworms poisonous? Polycladid flatworms are often brightly colored - a toxic warning to predators. Flatworms can be identified easily because, unlike nudibranchs, they do not have gills on their backs or other appendages.
Moving the sides of its body in a rippling motion, a flatworm crawls over corals. How do flatworms infect humans? The infection occurs when humans consume T. The result is that the eggs hatch and develop into a larval form that is capable of penetrating the intestinal wall and migrating through the body to form cysts in various tissues. Why are flatworms important to humans? Flatworms provide new insight into organ regeneration and the evolution of mammalian kidneys.
Summary: Our bodies are perfectly capable of renewing billions of cells every day but fail miserably when it comes to replacing damaged organs such as kidneys. What are some examples of flatworms? Flatworm species include: Turbellaria. Girardia tigrina. What are three examples of flatworms? Examples of Flatworms Trematoda. The class Trematoda consists of flukes. Over 1, species of tapeworms make up the class Cestoda.
The class Turbellaria is composed of approximately 3, species of planaria. Although they are tiny, they hunt continuously. Their prey is the smaller species in their aquatic environment. Flatworms serve an important role in the marine ecosystem. Flatworms feed primarily on protozoa and bacteria, smaller worms and any tiny animals, dead or alive, that they encounter. Depending on the species, flatworms also consume plant materials, such as algae.
Young flatworms might eat plants, but start feeding on animal matter as they mature. Adult flatworms can eat snails and immature bivalves, including clams and mollusks.
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