TrematodaTrematoda is a class within the phylum Platyhelminthes. It includes two groups of parasitic flatworms, known as flukes. They are interna parasites of mollusks and vertebrates. Most trematodes have a complex life cycle in which they use at least two hosts. Their primary host, where they sexually reproduce, is always a vertebrate. The second host, in which asexual reproduction occurs, is most times a snail.
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Skeletal Structure |
Trematodes are flat oval or worm-like animals, usually no more than a few centimeters in length. Their most distinctive external feature is the presence of two suckers, one close to the mouth, and the other on the bottom of the animal. The body surface of trematodes comprises a tough tissue which helps protect against digestive enzymes in those species that inhabit the gut of larger animals. It is also the surface of gas exchange; there are no respiratory organs The mouth is located at the forward end of the animal, and opens into a muscular, pumping pharynx. The pharynx connects, through the oesophagus, to one or two blind-ending caeca, which occupy most of the length of the body. In some species, the caeca are themselves branched. As in other flatworms, all waste material must be expelled through the mouth.
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