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Neurogenesis occurs in Cnidaria not only during developmental stages, but also in adults. Hydra, a genus belonging to Cnidaria, is used as a model organism to study nerve nets. In the body column of Hydra, there is continuous division of epithelial cells occurring while the size of the Hydra remains constant.
Hydra generally react in the same way regardless of the direction of the stimulus, and this may be due to the simplicity of the nerve nets. Hydra are generally sedentary or sessile, but do occasionally move quite readily, especially when hunting. They have two distinct methods for moving – 'looping' and 'somersaulting'.
Although freshwater is an unusual habitat for cnidarians, it is not unheard of, especially within hydrozoans. [2] For instance, the model organism Hydra and the jellyfish Craspedacusta sowerbii are both exclusively freshwater hydrozoans. [2] Hydra and Craspedacusta sowerbii are distantly related and are not closely related to Polypodium.
Cnidarians range in size from a mere handful of cells for the parasitic myxozoans [31] through Hydra's length of 5–20 mm (1 ⁄ 4 – 3 ⁄ 4 in), [40] to the lion's mane jellyfish, which may exceed 2 m (6 ft 7 in) in diameter and 75 m (246 ft) in length. [41] Prey of cnidarians ranges from plankton to animals several times larger than ...
4 Cnidaria. 5 Hemichordata. 6 Echinodermata. 7 Cephalocordata. 8 Tunicata. 9 Vertebrata. ... Hydra vulgaris, (previously Hydra magnipapillata), a model hydrozoan ...
Hydra viridissima is a species of cnidarian which is commonly found in still or slow-moving freshwater [2] in the Northern temperate zone. Hydra viridissima is commonly called green hydra due to its coloration, which is due to the symbiotic green algae Chlorella vulgaris which live within its body. [ 3 ]
Coelenterata is a term encompassing the animal phyla Cnidaria (corals, true jellies, sea anemones, sea pens, and their relatives) and Ctenophora (comb jellies). The name comes from Ancient Greek κοῖλος (koîlos) 'hollow' and ἔντερον (énteron) 'intestine', referring to the hollow body cavity common to these two phyla.
Hydra. Hydras are a genus of the Cnidaria phylum. All cnidarians can regenerate, allowing them to recover from injury and to reproduce asexually. Hydras are simple, freshwater animals possessing radial symmetry and contain post-mitotic cells (cells that will never divide again) only in the extremities. [14] All hydra cells continually divide. [15]