Search results
Results From The WOW.Com Content Network
The medusae of hydrozoans are smaller than those of typical jellyfish, ranging from 0.5 to 6 cm (0.20 to 2.36 in) in diameter. Although most hydrozoans have a medusoid stage, this is not always free-living and in many species exists solely as a sexually reproducing bud on the surface of the hydroid colony.
Hydra (/ ˈ h aɪ d r ə / HY-drə) is a genus of small freshwater hydrozoans of the phylum Cnidaria.They are native to the temperate and tropical regions. [2] [3] The genus was named by Linnaeus in 1758 after the Hydra, which was the many-headed beast of myth defeated by Heracles, as when the animal has a part severed, it will regenerate much like the mythical hydra's heads.
Jellyfish, also known as sea jellies, are the medusa-phase of certain gelatinous members of the subphylum Medusozoa, which is a major part of the phylum Cnidaria. Jellyfish are mainly free-swimming marine animals, although a few are anchored to the seabed by stalks rather
Medusozoa includes the classes Staurozoa, Cubozoa, Scyphozoa and Hydrozoa, but the relationships between these are unclear. Analysis using ribosomal RNA subunits suggests that within Medusozoa, Staurozoa was the first group to diverge, with Cubozoa and Scyphozoa forming a clade, a sister group to Hydrozoa.
In the hydrozoan jellyfish Clytia hemisphaerica, nematogenesis takes place at the base of the tentacles, as well as in the manubrium. At the base of the tentacles, nematoblasts proliferate then differentiate along a proximal-distal gradient , giving rise to mature nematocytes in the tentacles through a conveyor belt system.
The gastrovascular cavity or coelenteron of the flower hat jelly, Olindias formosa (arrow #2, colored gray) Gastrovascular system of the flatworm Dugesia , colored yellow 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 ...
Turritopsis dohrnii, also known as the immortal jellyfish, is a species of small, biologically immortal jellyfish [2] [3] found worldwide in temperate to tropic waters. It is one of the few known cases of animals capable of reverting completely to a sexually immature, colonial stage after having reached sexual maturity as a solitary individual.
The mesoglea is sandwiched between the epidermis and the gastrodermis. In some jellyfish the epidermis on the umbrella/bell surface seems to break off when the jellyfish grows so the mesoglea of older jellyfish is directly exposed to the water. [8] The mesoglea itself consists of multiple layers that can be differentiated by their electron density.