![]() ![]() Many flatworms are parasitic, including important parasites of humans. All of the remaining flatworms discussed here are part of the Rhabditophora. However, the offspring do not fully attach from the parents and, resemble a chain in appearance. These worms typically reproduce asexually by budding. The Catenulida, or "chain worms" is a small clade of just over 100 species. ![]() The Platyhelminthes consist of two lineages: the Catenulida and the Rhabditophora. Most of the flatworms are classified in the superphylum Lophotrochozoa, which also includes the mollusks and annelids. The flatworms are acoelomate organisms that include many free-living and parasitic forms. It also means the beginning of cephalization, the evolution of a concentration of nervous tissues and sensory organs in the head of the organism, which is where it first encounters its environment. ![]() These phyla are also bilaterally symmetrical, meaning that a longitudinal section will divide them into right and left sides that are symmetrical. The lophotrochozoans are triploblastic and possess an embryonic mesoderm sandwiched between the ectoderm and endoderm found in the diploblastic cnidarians. Trochophore larvae are characterized by two bands of cilia around the body. These clades are upheld when RNA sequences are compared. Lophophorata include the flatworms and several other phyla. The lophophores include groups that are united by the presence of the lophophore, a set of ciliated tentacles surrounding the mouth. ![]() This layer multiplies into a band and then splits internally to form the coelom this protostomic coelom is hence termed schizocoelom.Īs lophotrochozoans, the organisms in this superphylum possess either a lophophore or trochophore larvae. This is called protostomy or âfirst mouth.â In protostomy, solid groups of cells split from the endoderm or inner germ layer to form a central mesodermal layer of cells. Animals belonging to superphylum Lophotrochozoa are protostomes, in which the blastopore, or the point of involution of the ectoderm or outer germ layer, becomes the mouth opening to the alimentary canal. ![]()
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