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Nuda is a class of Ctenophora known as comb jellies, all of which have no tentacles.

Nuda (also Atentaculata) is the scientific name of a class of Rippenquallen (Ctenophora) and refers to the characteristic characteristic of representatives of this Taxons, the absence of Tentakeln. They are confronted classically the tentakelbewehrten Tentaculata. The group, which covers the two kinds Beroe and Neis, possesses to today no German names.

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Into the Mesogloea - thus the jelly-like intermediate layer between outside and interior skin (epidermis and Gastrodermis) - convenient pigments many Nuda kinds lend an easily rosa colouring, with Neis cordigera are additionally a strong orange examination trained. Nuda representatives reach a length of up to approximately thirty centimeters, whereby Neis is called cordigera frequently as the largest kind. The bag-like body is compressed with the Beroe kinds perpendicularly to the throat level easily, with Neis is still more strongly pronounced this flattening by training of two "seitenfluegel" (more for this in the section Systematik).Das named-giving and defining characteristic of the Nuda is the perfect absence of Tentakeln. Differently than with individual Tentaculata kinds, with which the Tentakel can have strongly diminished, Tentakelscheiden are present also in no life stage

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Mouth opening and muskulaturDa booty as a whole with the mouth, have this and that are devoured directly under it following throat a diameter large compared with other Rippenquallen. In order in particular to lower when swimming and with the pursuit of booty the water resistance, it can be sealed by a zipper-similar mechanism firmly, so that the front end of the Rippenqualle accepts streamline form. With this sealing become opposite throat sides, which tooths "lips" closely with one another, not only in close contact brought, but by temporarily trained cell cell connections. The all Rippenquallen own nerve net is consolidated within the "lips" the Nuda to one from approximately 40 nerve cell extensions (new rites) existing bundles.

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The mouth is opened and locked by the interaction of three different muscle types: In the Mesogloea run both circularly around the longitudinal axis of the animal arranged and radial, radially from the inside outward current muscle fibers; they work together with longitudinal, thus lengthwise-laterally aligned fibers, which lie in the epidermis. With Nuda kinds occurs excluding smooth musculature.

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Directly within the mouth opening characteristic finger shaped excrescences, the macro cilia are in the lining of the throat. With these 1844 of J. G. F. want described and 1965 of George Adrian Horridge with their current name provided structures concern it conically formed bundles surrounded by a common plasma membrane for the first time from two to three thousand scourges (cilia), which are connected to a functional unit as in the comb panels of the ribs. The particulars, between 35 and 60 micrometers are enough and in the diameter five to ten micrometers thicken cilia form together in the cross section a hexagonal structure and are perpendicularly to the common flapping direction by transverse bracings connected with one another; they do not possess a separate diaphragm, which would separate them from their neighbour scourges, however. Each cilium shows the structure from nine outside and two internal Mikrotubuli, typical for organisms with genuine cell core.

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The scourge cells, at which the cilia rise from individual Basalkoerperchen, participate bent and like roofing tiles one above the other stacked in relation to the throat lining around on the average thirty degrees to the mouth-turned away side. Thus the macro cilia always point toward the throat inside. There also the effective impact is arranged, which carries hiving hurry in synchronized waves like an assembly-line into the stomach; the throat musculature carries this procedure.

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Macro cilia run out in a dreizaehnigen point; this is rigidly enough, in order to tear the soft external wall up larger booty animals like other Rippenquallen; proteolytic (protein-decomposing) enzymes, which penetrate into the developed wounds, make the victim then fast escape unable. Macro cilia take over thus also the function of teeth and can as the Tentakeln of the Tentaculata appropriate catch structures of the Nuda be regarded.

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Out as with all Rippenquallen channels pull inside duct system of the central stomach into all body regions. Each comb rib is supplied by its own Meridionalkanal, which is convenient below these directly. It possesses numerous excrescences branched out finely, of which some unite with the throat, with the Nuda kinds others against it blindly ends. To the mouth end the Meridionalkanaele gathers in a circle in one around the mouth zirkumoralen ring channel lain.

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Statocyste and polplatten as with all Rippenquallen the equal yielding organ, the Statocyste at the mouth-turned away side, which specifies also the clock for the comb panels located on the ribs, is. The impact impulse is passed on differently than for instance with the Lobata not through between the comb panels running scourge volumes, but thus that the individual comb panels tilt in sequence and affect like dominos the following panel.

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Directly below the Statocyste is a recessing lined with sensory cells; the epithelium fabric contained in it continues to the mouth in two facing narrow scourge volumes, which are called in the throat level of the Rippenqualle run and polplatten. They cause to a water flow by their impact over the Statocyste and are with the Nuda kinds at their edge with finger-like excrescences, which Papillen occupied, whose function is still unsettled, serves, probably in addition, the sensory perception.

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Spreading and habitat the group occur world-wide in all oceans and seas, where the animals live fully floating (pelagisch) in the plankton. Differently than other groups of Rippenquallen they use their comb ribs for progressive movement almost exclusively.

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Nutrition Nuda kinds nourish themselves of fully floating animals with soft body, primarily of other Rippenquallen, which can be quite larger than it. The booty is looked for actively and devoured usually as a whole; with oversizing the animals can use their macro cilia as teeth, in order to pull thereby pieces of fabric out from the victim.

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Meaning as Neozoon after to the late 1980er years the Rippenquallen kind Mnemiopsis leidyi by ballast water into the black sea was probably introduced and there a population explosion went through, in whose process anchovy fishing broke down completely, stabilized the ecological system again, when 1997 a further Rippenquallen kind emerged, which to the Nuda counted Beroe ovata, which nourishes itself almost exclusively of Mnemiopsis leidyi. Also the Beroe population through-lived first an explosion of the individual number to finally two existence rapidly broke down. Both Mnemiopsis are nevertheless leidyi and Beroe ovata today and Neozoen in the black sea established. The same phenomenon plays itself at the beginning 21. Century in the Kaspi sea off.

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Thus hermaphrodites reproduce themselves and have reproduction all kinds in sexual way both over female and male gonads, are. Although no detailed data are present, is assumed self fertilization is with Nuda kinds rather the exception. From the fertilized eggs young animals follow, which already look like a miniature version of the adult of animal and therefore not when larva should be designated. To them Tentakel and Tentakelscheiden are already missing, otherwise they resemble the Cydippea stage of the tentakelbesetzten Rippenquallen.

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Fossil Nuda kinds are not well-known, so that the masterhistorical development of the group from the comparison with other modern representatives of the Rippenquallen must be opened. In the traditional system the Nuda of the class of the Tentaculata is confronted, which summarize all kinds, which have contrary to the Nuda kinds at least rudimentary Tentakel. This organization however probably does not show the actual verwandtschaftsverhaeltnisse after provisional results of molecular-genetic and morphologic studies within the Rippenquallen. Although systematics are still in the river and still no independent evaluation of the findings is present, a family from the order seems Cydippida, Haeckelidae, to belong into the closer relationship of the Nuda kinds; neither Cydippida nor Tentaculata would be thus monophyletische Taxa, covered thus not all descendants of their common moving forward and therefore of modern systematics not as valid Taxon were recognized.

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The Monophylie of the Nuda themselves against it is to a large extent undisputed, there the complete Tentakelverlust as well as the presence common characteristics (Synapomorphien), derived from macro cilia as, to be regarded can.

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Systematics one differentiate between about 25 kinds, which divide themselves on two kinds, Beroe and Neis, which into the same family Beroidae and order Beroida are placed. Family and order 1825 and/or 1829 by the German Naturalisten Johann Friedrich Eschscholtz introduction those kind Beroe enclosure nearly all kinds of the class and is world-wide common. One the most well-known is also the Melonenqualle spread in the North Sea (Beroe gracilis). With Beroe kinds the mouth-turned away (aborale) side is rounded off.

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The kind Neis is monotypical, contains thus only a kind, Neis cordigera (Lesson 1824), and exclusively occurs in waters around Australia. With this kind two bend-like extensions are on the aboralen page, so that the centrically lying in between aborale sense pole is not contrary to the Beroiden at the outermost body end (consider kind name cordigera: Heart form). The bend-like extensions extend along the flanks of the animal and are split in the longitudinal process, so that the impression of two lateral "doppelfluegeln" develops. At the edges of these four "wings" in each case a rib volume runs. The remaining four rib volumes run over (relative to the "seitenfluegeln") the "upper" and "lower" body half. The Rippenquallen typical eight-number of the rib volumes is thus received, even if the volumes are trained in two groups of different lengths due to the special body form.