Fish tapeworm
The fish tapeworm (Diphyllobothrium latum) is a large parasitic organism commonly found in the intestines of mammals, including humans, particularly in the Northern Hemisphere. It is transmitted to humans primarily through the consumption of poorly cooked fish, such as trout, salmon, pike, and perch. This tapeworm can grow to more than 30 feet (9 meters) in length and features a long, flat, segmented body composed of square, paper-thin segments known as proglottids. These proglottids absorb nutrients from the host's digestive fluids, which can lead to nutritional deficiencies, such as vitamin B12 deficiency, anemia, abdominal discomfort, and weight loss in the human host.
Fish tapeworms are bilaterally symmetrical and possess a distinct head equipped with suckers and hooks that anchor them to the intestinal lining. They reproduce asexually, with each proglottid containing both male and female reproductive organs. When detached from the main body, these segments release eggs into the environment, which can survive for years before developing into larvae. These larvae are then consumed by crustaceans and subsequently by fish, continuing the life cycle of the tapeworm. The fish tapeworm can reside in human intestines for several years, often remaining undetected for a significant period, with a lifespan of up to 25 years.
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Fish tapeworm
The fish tapeworm is common in the Northern Hemisphere in the intestines of mammals, including humans. As its name suggests, it is passed to mammals through poorly cooked fish, such as trout, salmon, pike, and perch.
Kingdom: Animalia
Phylum: Platyhelmithes
Class: Cestoda
Order: Pseudophyllidea
Family: Diphyllobothriidae
Genus: Diphyllobothrium
Species: Latum
The fish tapeworm is among the largest parasites that can infect humans. They are most common in the Northern Hemisphere. Like other tapeworms, it is a long, flat, segmented creature that may be more than 30 feet (9 meters) long. Each of the segments of a fish tapeworm's body is square, flat, and paper-thin. These segments are called proglottids. Proglottids rest in the digestive fluids and soak up nutrients for the fish tapeworm. The fish tapeworm is being fed and nourished by the same substances that usually digest, or break down, cells. As the fish tapeworm eats, the human host loses the nourishment that is being soaked up by the fish tapeworm. This may lead to a vitamin B12 deficiency, anemia, abdominal discomfort, and weight loss.
Like other members of the phylum Platyhelminthes, fish tapeworms are bilaterally symmetrical. This means the two sides of their bodies are the same. Humans are bilaterally symmetrical. If a human is split in half from top to bottom, the two sides would be mirror images of one another.
In addition to its long, bilaterally symmetrical body and its many segments, the fish tapeworm has a distinct head. This head is covered by suckers and hooks which it digs into the lining of the intestine to get a firm grip on its host.
Once firmly settled in the intestine, the fish tapeworm spends its life eating its host's digestive fluids. Although it lives inside fish as an intermediate host, it eventually finds its way to the intestinal tracks of humans and other fish-eating mammals. Like beef and pork tapeworms, the fish tapeworm moves from host to host because its first host serves as prey for its final host.
Fish tapeworms reproduce asexually, or individually. Each of the proglottids of their bodies is equipped with male and female sexual organs and can reproduce. Proglottids at the end of a fish tapeworm's body produce eggs and then split off from the rest of the proglottids. These eggs are carried out of the host's body in waste products. Through sanitary procedures, these wastes make their way into the water. Eggs can survive for years waiting for the right environment to develop.
Once in the water, the fish tapeworm eggs develop into hairlike larvae. They are eaten by tiny crustaceans and later by fish. Once inside the fish they migrate into the creatures' muscles and rest there in the form of cysts. From this first host, the life cycle of the fish tapeworm continues until each egg deposited from the first host has developed into a mature fish tapeworm living in the intestine of a fish-eating mammal.
The life span of the fish tapeworm is up to 25 years. They can live in human intestines for several years before they are detected.
Bibliography
"Diphyllobothrium Latum (and Other Species) FAQs." The Centers for Disease Control and Prevention, 17 Sept. 2020, www.cdc.gov/parasites/diphyllobothrium/faqs.html. Accessed 5 Apr. 2024.
Kruse, D. and S. Herhilan. "Diphyllobothrium Latum." Animal Diversity Web, animaldiversity.org/accounts/Diphyllobothrium‗latum. Accessed 5 Apr. 2024.