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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 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.
Tegument / ˈ t ɛ ɡ j ʊ m ə n t / is a term in helminthology for the outer body covering of members of the phylum Platyhelminthes. The name is derived from a Latin word tegumentum or tegere, meaning "to cover". [1] [2] It is characteristic of flatworms including the broad groups of tapeworms and flukes.
The most common corals in the subclass Hexacorallia have a hexameric body plan; their polyps have six-fold internal symmetry and a number of tentacles that is a multiple of six. Octamerism is found in corals of the subclass Octocorallia. These have polyps with eight tentacles and octameric radial symmetry.
They lack body cavities (acoelomate structure), a hindgut or an anus. [1] The epidermal cells of acoelomorphs are unable to proliferate, a feature that is only shared with rhabditophoran flatworms and was for some time considered a strong evidence for the position of Acoelomorpha within Platyhelminthes. In both groups, the epidermis is renewed ...
Download as PDF; Printable version; ... Platyhelminthes: Order: ... All species of Dugesiidae live in freshwater environments and have a dorsoventrally flattened body ...
The gastrovascular cavity is the primary organ of digestion and circulation in two major animal phyla: the Coelenterates or cnidarians (including jellyfish and corals) and Platyhelminthes (flatworms). The cavity may be extensively branched into a system of canals.
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.