The Platyhelminthes, or flatworms, are a phylum consisted of unsegmented, soft-bodied invertabres. They have no specialized circulatory and respiratory organs with restrict them to having a flat shape which allows oxygen and nutrients to pass through their bodies only by diffusion. They have only one opening for digestive which controls what comes in and out of the body not allowing them to process food non-stop. There are three types of flatworms and they are:
1. Planarians (Turbellaria)
2. Flukes (Trematoda)
3. Tapeworms (Cestoda)
1. Planarians (Turbellaria)
2. Flukes (Trematoda)
3. Tapeworms (Cestoda)
Hymenolepis nana (dwarf tapeworm)
The dwarf tapeworm, as well as all other tape worms work without a digestive system. They feed by the absorption of nutrients in the intestinal lumen. They do not have any specific carbohydrate requirements and will mostly absorb anything that is being passed through the intestine at that time. When it reaches the adult stage, it will latch onto the intestinal walls and have its “segments” or teeth reaching out into intestinal space to absorb food. These tapeworms can be very harmful to children by absorbing the nutrients in the food that a child has eaten whereas to adults they are mostly just annoying. Usually one specific tapeworm will not be damage but many can be extremely harmful especially to children with weak immune systems.
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Halipegus eccentricus (fluke)
The Halipegus has a sub terminal oral sucked and a short esophagus. It has a two branched gut that extends throughout the body without a very long pharynx. They live inside the digestive systems of an infected animal, usually a frog or a snail, and they can simply absorb pre-digested food from the animal. Since they don’t have to contribute any energy or body volume to digestion, this leaves these animals more energy and body space to devote to reproduction. Most trematodes have a pair of suckers on their surfaces, which they use to attach themselves to the insides of the infected animal's body tubes. Typically, there is an oral sucker that surrounds the mouth, and aventral sucker closer to the animal’s rear end.
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Caenoplana coerulea (blue flatworm)
The digestive system of a blue flatworm is quite similar to that of a general flat worm. It lacks an anus so whatever nutrients that is absorbed through the mouth comes back out as waste from the same portal. This restricts them from continuously breaking down food like a human or a dog. Sometimes to provide more surface area, their gut becomes more complex but very rarely are there any other organs involved with the digestion of a blue flat worm.
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