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Hydra (/ ˈ h aɪ d r ə / HY-drə) is a genus of small freshwater hydrozoans of the phylum Cnidaria.They are solitary, carnivorous jellyfishlike animals, [2] native to the temperate and tropical regions.
Pacific sea nettles, Chrysaora fuscescens. Cnidaria (/ n ɪ ˈ d ɛər i ə, n aɪ-/ nih-DAIR-ee-ə, NY-) [4] is a phylum under kingdom Animalia containing over 11,000 species [5] of aquatic invertebrates found both in fresh water and marine environments (predominantly the latter), including jellyfish, hydroids, sea anemones, corals and some of the smallest marine parasites.
They act as intermediate hosts of endoparasitic helminths, with the infection being transferred to the definitive host fish after predation. Some digenean trematodes, especially species in the family Lepocreadiidae, use jellyfish as their second intermediate hosts. Fish become infected by the trematodes when they feed on infected jellyfish ...
Polyp prey includes copepods and fish larvae. [2] Longitudinal muscular fibrils formed from the cells of the ectoderm allow tentacles to contract when conveying the food to the mouth. Similarly, circularly disposed muscular fibrils formed from the endoderm permit tentacles to be protract or thrust out once they are contracted.
Hydrozoa (hydrozoans; from Ancient Greek ὕδωρ (húdōr; "water") and ζώα (zóa; "animals")) is a taxonomic class of individually very small, predatory animals, some solitary and some colonial, most of which inhabit saline water.
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 ]
Hydra vulgaris, the fresh-water polyp, [3] is a small freshwater hydroid with length from 10 mm to 30 mm and width about 1 mm. [4] Description.
Polypodium has traditionally been considered a cnidarian because it possesses nematocysts, the stinging structures characteristic of this phylum. [2] Molecular phylogenetic studies using 18S rDNA sequence data temporarily challenged this interpretation, by finding that Polypodium is a close relative to myxozoans and suggesting that together ...