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The Platyhelminthes have very few synapomorphies - distinguishing features that all Platyhelminthes (but no other animals) exhibit. This makes it difficult to work out their relationships with other groups of animals, as well as the relationships between different groups that are described as members of the Platyhelminthes.
Monogenea are Platyhelminthes, so are among the lowest invertebrates to possess three embryonic germ layers—endoderm, mesoderm, and ectoderm. In addition, they have a head region that contains concentrated sense organs and nervous tissue (brain). Like all ectoparasites, monogeneans have well-developed attachment structures.
The Turbellaria are one of the traditional sub-divisions of the phylum Platyhelminthes (flatworms), and include all the sub-groups that are not exclusively parasitic.There are about 4,500 species, which range from 1 mm (0.039 in) to large freshwater forms more than 500 mm (20 in) long [3] or terrestrial species like Bipalium kewense which can reach 600 mm (24 in) in length.
The Platyhelminthes and Gastrotricha are acoelomate. The other phyla have a pseudocoel, and share characteristics such as the structure of their jaws and pharynx, although these have been secondarily lost in the parasitic Acanthocephala. They form a monophyletic subgroup called the Gnathifera.
The phylum Platyhelminthes includes two classes of worms of particular medical significance: the cestodes (tapeworms) and the trematodes (flukes and blood flukes), depending on whether or not they have segmented bodies. [1] [8] There may be as many as 300,000 species of parasites affecting vertebrates, [9] and as many as 300 affecting humans ...
Liver fluke is a collective name of a polyphyletic group of parasitic trematodes under the phylum Platyhelminthes. [1] They are principally parasites of the liver of various mammals, including humans. Capable of moving along the blood circulation, they can occur also in bile ducts, gallbladder, and liver parenchyma. In these organs, they ...
Cestoda is a class of parasitic worms in the flatworm phylum (Platyhelminthes). Most of the species—and the best-known—are those in the subclass Eucestoda; they are ribbon-like worms as adults, commonly known as tapeworms. Their bodies consist of many similar units known as proglottids—essentially packages of eggs which are regularly shed ...
Digenea (Gr. Dis – double, Genos – race) is a class of trematodes in the Platyhelminthes phylum, consisting of parasitic flatworms (known as flukes) with a syncytial tegument and, usually, two suckers, one ventral and one oral.