/ten"euh fawr', -fohr', tee"neuh-/, n.any gelatinous marine invertebrate of the phylum Ctenophora; a comb jelly.[1880-85; < NL ctenophorus. See CTENO-, -PHORE]
* * *or comb jellyAny of nearly 90 species (phylum Ctenophora) of usually colourless marine invertebrates that have a series of vertical ciliary combs over their bodies.Ctenophores are sometimes mistaken for jellyfish. The body is round or spherical, with tentacles to capture food, and the combs beat to provide locomotion. Most species are small (not much greater than 0.1 in. [3 mm] in diameter), but at least one species grows larger than 3 ft (1 m). Ctenophores live in almost all ocean regions, floating freely in the water. All comb jellies except one parasitic species are carnivores, consuming young mollusks, crustacean and fish larvae, copepods, and other zooplankton.
* * *▪ phylum of invertebrateIntroductionbyname Comb Jelly,any of the numerous marine invertebrates constituting the phylum Ctenophora. The phylum derives its name (from the Greek ctene, or “comb,” and phora, or “bearer”) from the series of vertical ciliary combs over the surface of the animal. The body form resembles that of the cnidarian medusa. Various forms of ctenophores are known by other common names—sea walnuts, sea gooseberries (sea gooseberry), cat's-eyes.Though comb jellies are, for the most part, of small size, at least one species, the Venus's girdle, may attain a length of more than 1 m (3 feet). One parasitic species is only 3 mm (1/8 inch) in diameter. Some ctenophores live in somewhat brackish water, but all are confined to marine habitats. They live in almost all ocean regions, particularly in surface waters near shores. At least two species (Pleurobrachia pileus and Beroe cucumis) are cosmopolitan, but most have a more restricted distribution.Apart from a few creeping and parasitic species, ctenophores float freely suspended in the water. They are frequently swept into vast swarms, especially in bays, lagoons, and other coastal waters. Except for one parasitic species, all of them are carnivorous, eating myriads of small planktonic animals. When abundant in a region, ctenophores consume most of the young of fish, larval crabs, clams, and oysters, as well as copepods and other planktonic animals that would otherwise serve as food for such commercial fish as sardines and herring. In turn, however, comb jellies are themselves consumed by certain fish.Natural history.Ctenophores are hermaphroditic; eggs and sperm (gametes) are produced in separate gonads along the meridional canals that house the comb rows. In most ctenophores, these gametes are released into the water, where fertilization and embryonic development take place. In Pleurobrachia and in other Cydippida, the larva closely resembles the adult, so that there is little change with maturation. Most ctenophores, however, have a so-called cydippid larva, which is ovoid or spherical with two retractable tentacles. The metamorphosis of the globular cydippid larva into an adult is direct in ovoid-shaped adults and rather more prolonged in the members of flattened groups. Only the parasitic Gastrodes has a free-swimming planula larva comparable to that of the cnidarians.Form and function.Most ctenophores are colourless, although Beroe cucumis is pink and the Venus's girdle (Cestum veneris) is delicate violet. The colourless species are transparent when suspended in water, except for their beautifully iridescent rows of comb plates. Most of the comb jellies are bioluminescent; they exhibit nocturnal displays of bluish or greenish light that are among the most brilliant and beautiful known in the animal kingdom.Most of the nearly 90 known species of comb jellies are spherical or oval, with a conspicuous sense organ (the statocyst) at one end (aboral) of the body and a mouth at the other end (oral). The eight comb rows that extend orally from the vicinity of the statocyst serve as organs of locomotion. Each comb row is made up of a series of transverse plates of very large cilia, fused at the base, called combs. When the cilia beat, the effective stroke is toward the statocyst, so that the animal normally swims oral end first. The more primitive forms (order Cydippida) have a pair of long, retractable branched tentacles that function in the capture of food. The tentacles are richly supplied with adhesive cells called colloblasts, which are found only among ctenophores. These cells produce a sticky secretion, to which prey organisms adhere on contact.The mouth leads into a tubular pharynx, from the aboral end of which arises a complex, branched series of canals that make up the digestive tract. Since this structure serves both digestive and circulatory functions, it is known as a gastrovascular cavity. Ctenophores have no true anus; the central canal opens toward the aboral end by two small pores, through which a small amount of egestion can take place.Gonads develop as thickenings of the lining of the digestive canals. The nervous system is a primitive nerve network, somewhat more concentrated beneath the comb plates. It is similar to the cnidarian nervous system. There is no trace of an excretory system.The outside of the body is covered by a thin layer of ectodermal cells, which also line the pharynx. A second thin layer of cells, constituting the endoderm, lines the gastrovascular cavity. Between the ectoderm and the endoderm is a thick gelatinous layer, the mesoglea. Because it contains not only many mesenchymal cells (or unspecialized connective tissue) but also specialized cells (e.g., muscle cells), the mesoglea forms a true mesoderm. In this respect the comb jellies are more highly evolved than even the most complex cnidarians (cnidarian).Classification.Ctenophores and cnidarians were formerly placed together in the phylum Coelenterata. Modern authorities, however, have separated the cnidarians and ctenophores on the basis of the following ctenophore characteristics: (1) the lack of the stinging cells (nematocysts) that are characteristic of cnidarians; (2) the existence of a definite mesoderm in the ctenophores; (3) fundamental differences in embryological development between the two groups; and (4) the biradial symmetry of ctenophores. It is, however, generally thought that ctenophores and cnidarians share a common evolutionary ancestor.
* * *
Look at other dictionaries:
Ctenophore — Cten o*phore (t?n ? f?r), n. (Zo[ o]l.) One of the Ctenophora. [1913 Webster] … The Collaborative International Dictionary of English
ctenophore — [ten′ə fôr΄, tē′nəfôr΄] n. [ CTENO + PHORE] any of a phylum (Ctenophora) of sea animals with an oval, transparent, jellylike body bearing eight rows of comblike plates that aid in swimming … English World dictionary
Cténophore — Ctenophora Traduction à relire Ctenophore → … Wikipédia en Français
Ctenophore — Taxobox name = Comb jellies image caption = Ctenophorae from Ernst Haeckel s Kunstformen der Natur , 1904 domain = Eukaryota regnum = Animalia phylum = Ctenophora phylum authority = Eschscholtz, 1829 subdivision ranks = Classes subdivision =… … Wikipedia
cténophore — ● cténaire ou cténophore nom masculin Animal diploblastique marin, pélagique, transparent, à symétrie bilatérale et souvent dorsiventrale, se déplaçant par le mouvement de rangées méridiennes de palettes ciliées et capturant ses proies à l aide… … Encyclopédie Universelle
ctenophore — noun Etymology: ultimately from Greek kten , kteis + pherein to carry more at bear Date: circa 1882 any of a phylum (Ctenophora) of marine animals superficially resembling jellyfishes but having biradial symmetry and swimming by means of eight… … New Collegiate Dictionary
Ctenophore — … Википедия
ctenophore — noun Any of various marine animals of the phylum Ctenophora, having lucent, mucilaginous bodies bearing eight rows of comblike cilia used for swimming. Syn: comb jelly … Wiktionary
ctenophore — [ ti:nəfɔ:, tɛ ] noun Zoology an aquatic invertebrate of the small phylum Ctenophora, which comprises the comb jellies. Origin from mod. L. Ctenophora, from Gk kteis, kten comb + pherein to bear … English new terms dictionary
ctenophore — cteno·phore … English syllables