What is "ctenophora"

Animal \An"i*mal\, a. [Cf. F. animal.]

1. Of or relating to animals; as, animal functions.

2. Pertaining to the merely sentient part of a creature, as distinguished from the intellectual, rational, or spiritual part; as, the animal passions or appetites.

3. Consisting of the flesh of animals; as, animal food.

   Animal magnetism. See Magnetism and Mesmerism.

   Animal electricity, the electricity developed in some animals, as the electric eel, torpedo, etc.

   Animal flower (Zo["o]l.), a name given to certain marine animals resembling a flower, as any species of actinia or sea anemone, and other Anthozoa, hydroids, starfishes, etc.

   Animal heat (Physiol.), the heat generated in the body of a living animal, by means of which the animal is kept at nearly a uniform temperature.

   Animal spirits. See under Spirit.

   Animal kingdom, the whole class of beings endowed with animal life. It embraces several subkingdoms, and under these there are Classes, Orders, Families, Genera, Species, and sometimes intermediate groupings, all in regular subordination, but variously arranged by different writers.

   Note: The following are the grand divisions, or subkingdoms, and the principal classes under them, generally recognized at the present time: Vertebrata, including Mammalia or Mammals, Aves or Birds, Reptilia, Amphibia, Pisces or Fishes, Marsipobranchiata (Craniota); and Leptocardia (Acrania). Tunicata, including the Thaliacea, and Ascidioidea or Ascidians. Articulata or Annulosa, including Insecta, Myriapoda, Malacapoda, Arachnida, Pycnogonida, Merostomata, Crustacea (Arthropoda); and Annelida, Gehyrea (Anarthropoda). Helminthes or Vermes, including Rotifera, Ch[ae]tognatha, Nematoidea, Acanthocephala, Nemertina, Turbellaria, Trematoda, Cestoidea, Mesozea. Molluscoidea, including Brachiopoda and Bryozoa. Mollusca, including Cephalopoda, Gastropoda, Pteropoda, Scaphopoda, Lamellibranchiata or Acephala. Echinodermata, including Holothurioidea, Echinoidea, Asterioidea, Ophiuroidea, and Crinoidea. C[oe]lenterata, including Anthozoa or Polyps, Ctenophora, and Hydrozoa or Acalephs. Spongiozoa or Porifera, including the sponges. Protozoa, including Infusoria and Rhizopoda. For definitions, see these names in the Vocabulary.

Ctenophora \Cte*noph"o*ra\ (t?-n?f"?-r?), n. pl. [NL., from Gr. ???, ???, comb + ???? to carry.] (Zo["o]l.) A phylum of invertebrates, commonly ellipsoidal in shape, swimming by means of eight longitudinal rows of paddles. They are commonly called the comb jellies, because the separate paddles somewhat resemble combs. This phylum was formerly classified as a subdivision (class) within the C[oe]lenterata.

Ctenophora is a genus of true crane flies. The species are large (about 20 mm long, with 25-mm wingspans), shiny black craneflies with large yellow, orange, or red markings to mimic wasps. Males have comb-like antennae. The larvae are saproxylic. The species are confined to old deciduous forests, orchards, and other habitats with continuity of the presence of dying and fallen trees. Ctenophora species are important bioindicators.

Ctenophora is distinguished from related genera ( Dictenidia Brulle, Phoroctenia Coquillett) by these characteristic combinations. The segments of the flagellum of the males have two pairs of outgrowths, the lower pair longer than upper pair. The antennae of the female are distinctly 13-segmented, and often indistinctly serrated. The sides of the mesothorax bear long bristles. Sternite 8 of the female is without dentate protuberances.

Ctenophora (; singular ctenophore, or ; from the Greek κτείς kteis 'comb' and φέρω pherō 'carry'; commonly known as comb jellies) is a phylum of invertebrate animals that live in marine waters worldwide. Their most distinctive feature is the ‘combs’ – groups of cilia which they use for swimming – they are the largest animals that swim by means of cilia. Adults of various species range from a few millimeters to in size. Like cnidarians, their bodies consist of a mass of jelly, with one layer of cells on the outside and another lining the internal cavity. In ctenophores, these layers are two cells deep, while those in cnidarians are only one cell deep. Some authors combined ctenophores and cnidarians in one phylum, Coelenterata, as both groups rely on water flow through the body cavity for both digestion and respiration. Increasing awareness of the differences persuaded more recent authors to classify them as separate phyla.

Ctenophores also resemble cnidarians in having a decentralized nerve net rather than a brain. Genomic studies have suggested that the neurons of Ctenophora, which differ in many ways from other animal neurons, evolved independently from those of the other animals.

Almost all ctenophores are predators, taking prey ranging from microscopic larvae and rotifers to the adults of small crustaceans; the exceptions are juveniles of two species, which live as parasites on the salps on which adults of their species feed. In favorable circumstances, ctenophores can eat ten times their own weight in a day. Only 100–150 species have been validated, and possibly another 25 have not been fully described and named. The textbook examples are cydippids with egg-shaped bodies and a pair of retractable tentacles fringed with tentilla ("little tentacles") that are covered with colloblasts, sticky cells that capture prey. The phylum has a wide range of body forms, including the flattened, deep-sea platyctenids, in which the adults of most species lack combs, and the coastal beroids, which lack tentacles and prey on other ctenophores by using huge mouths armed with groups of large, stiffened cilia that act as teeth. These variations enable different species to build huge populations in the same area, because they specialize in different types of prey, which they capture by as wide a range of methods as spiders use.

Most species are hermaphrodites—a single animal can produce both eggs and sperm, meaning it can fertilize its own egg, not needing a mate. Some are simultaneous hermaphrodites, which can produce both eggs and sperm at the same time. Others are sequential hermaphrodites, in which the eggs and sperm mature at different times. Fertilization is generally external, although platyctenids' eggs are fertilized inside their parents' bodies and kept there until they hatch. The young are generally planktonic and in most species look like miniature cydippids, gradually changing into their adult shapes as they grow. The exceptions are the beroids, whose young are miniature beroids with large mouths and no tentacles, and the platyctenids, whose young live as cydippid-like plankton until they reach near-adult size, but then sink to the bottom and rapidly metamorphose into the adult form. In at least some species, juveniles are capable of reproduction before reaching the adult size and shape. The combination of hermaphroditism and early reproduction enables small populations to grow at an explosive rate.

Ctenophores may be abundant during the summer months in some coastal locations, but in other places they are uncommon and difficult to find. In bays where they occur in very high numbers, predation by ctenophores may control the populations of small zooplanktonic organisms such as copepods, which might otherwise wipe out the phytoplankton (planktonic plants), which are a vital part of marine food chains. One ctenophore, Mnemiopsis, has accidentally been introduced into the Black Sea, where it is blamed for causing fish stocks to collapse by eating both fish larvae and organisms that would otherwise have fed the fish. The situation was aggravated by other factors, such as over-fishing and long-term environmental changes that promoted the growth of the Mnemiopsis population. The later accidental introduction of Beroe helped to mitigate the problem, as Beroe preys on other ctenophores.

Despite their soft, gelatinous bodies, fossils thought to represent ctenophores, apparently with no tentacles but many more comb-rows than modern forms, have been found in lagerstätten as far back as the early Cambrian, about . The position of the ctenophores in the evolutionary family tree of animals has long been debated, and the majority view at present, based on molecular phylogenetics, is that cnidarians and bilaterians are more closely related to each other than either is to ctenophores. A recent molecular phylogenetics analysis concluded that the common ancestor of all modern ctenophores was cydippid-like, and that all the modern groups appeared relatively recently, probably after the Cretaceous–Paleogene extinction event . Evidence accumulating since the 1980s indicates that the "cydippids" are not monophyletic, in other words do not include all and only the descendants of a single common ancestor, because all the other traditional ctenophore groups are descendants of various cydippids.