Stummelfuesser

Stummelfuesser
: Vielzeller (Metazoa)
: Fabric animals (Eumetazoa)
: Bilateria
: (Protostomia)
: Haeutungstiere (Ecdysozoa)
: Stummelfuesser
Onychophora

Those Stummelfuesser (Onychophora) form an own from the group that Haeutungstiere (Ecdysozoa) and leave themselves simplified as Worms describe with legs. Mainly in the Southern Hemisphere common, they live predatory on smaller animals as for example of large interest.

Stummelfuesser are very probably close also Gliederfuessern (Arthropoda) and (Tardigrada) related and form that with these two Panarthropoda. The first kind was scientifically described 1825 from landdown Guilding, that the animals still as modified Snails (Gastropoda) regarded; the name Onychophora was coined/shaped only 1853.

Table of contents

Structure

Stummelfuesser are wurmfoermige, segmented animals with cylindrical, belly-laterally flattened body cross section and reihenfoermig arranged unstructured appendices of body, the stub feet. The animals become long between 0,5 and 20 centimeters, whereby the average is with approximately 5 centimeters, and exhibit between 13 and 43 pairs of legs. The color of their of numerous fine transverse rings skin are often inconspicuously orange, red or brown, sometimes in addition, bright green, blue, goldfarben covered or know, occasionally also colored examined.

Outwardly inconspicuous and only segmenting identifiable by the regular distance of the pairs of legs is it shown in the regular lining up of skin openings (Ostien), elimination organs (Nephridien) and nerve cell concentrations (Ganglia). The individual body sections are hardly specialized; even the head develops only little differently than any abdomen segment. Segmenting apparent becomes by also the gene provable at other groups of animals engrailed specified, which is activated in each case during the Embryonalentwicklung at the rear segment border and in the growth zone of the stub feet.

Appendices of body

The named-giving characteristic of the Stummelfuesser those are technical as Lobopoden marked conical, bag-like appendices of body, which are hollow inside and exhibit no joints. Although their number between the kinds can vary considerably, they are in principle very similar itself in the structure. Their firmness is based on that the contained body fluid.

The legs are moved usually passively by contraction and stretch of the total body. In each leg runs however also internal muscles, which can shorten and bend it; due to the missing joints this buckling in each place can take place along the long side of the leg.

Two different organs are with some kinds within the legs:

  • Cruraldruesen glands lain are, into the body cavity the in-rich at the leg beginning. They open at lain the belly-laterally Cruralpapillen, small warzenfoermigen collections, outward and separate chemical messenger materials, so mentioned Pheromones, off. Their name leads itself from latin cruralis, "leg-referred", off.
  • Coxalvesikel, also as Coxalsaecke or Coxalorgane are designated, are on to belly-turn the side at the leg paragraph pouches lain, which can to be outward inverted and probably the water absorption serve. They come only within that the Peripatidae forwards and are after latin word for "hip", coxa, designated.

At the feet one pair each of retractable sits more hardened (more sklerotisierter) claws out Chitin, to which the scientific name of the Taxons is due, itself of the Greek one onyches, "claws" and pherein, "carry", derives. At the claw beginning are three to six thorny "cushions", on which the leg in resting position puts and runs on which the animals on on smooth underground; the claws are used mainly on uneven terrain, in order to attain firm stop.

Apart from the pairs of legs there are three further appendices of body, which are at the head consisting of three segments:

  • At the first head segment is a pair of geringter antennas, which serve the sensory perception. They do not correspond probably to the antennas that Gliederfuesser (Arthropoda), perhaps however of them "lips" or Labrum. At its beginning a pair is simpler except with few blind kinds . Before it various gruebchen, stilettartige structures are put on or thorns with many Australian kinds, whose function is not yet enlightened, but at least with some kinds the transfer of sperm cells packages (Spermatophoren) seems to serve.
  • At the second head segment is belly-laterally mouth opening surrounded by sense-sensitive "lips", the Labrum,; with Stummelfuessern the structure is however a muskuloeser excrescence of the throat and therefore despite the same name probably not homologous to the Labrum of the Gliederfuesser. Deeply within the oral cavity the sharp, crescent-shaped Kiefer lies or Mandibeln, which are strongly hardened and which claws of the legs resemble, which are probably homologous them. They are divided into outside and internal Mandibeln, are covered with fine denticles and move in longitudinal direction forwards and backwards; hunted booty can be zerraspelt in such a way into fine pieces.
  • At the third segment are on the left and on the right the mouth two as Mundpapillen designated openings, in which a pair large, internally strongly branched out Schleimdruesen flows. These are appropriate for instance in the center of the body and separate for the booty catch and the defense determined milchigweissen Schleim off. Sometimes the connecting "Schleimleiter" is thickened to a reservoir, which knows the before-produced Schleim buffers. Schleimdruesen are probably modified Cruraldruesen.

All three structures correspond to their evolutionary origin after the pairs of legs of the other segments.

Skin and musculature

Differently than the Gliederfuesser Stummelfuesser firm do not possess (Exoskelett). Instead their body form is maintained as with a water-filled balloon with the easily increased pressure of the interior liquid on the body wall: Because this liquid is incompressible with the pressures arising by muscle power, thus its volume does not change, can for muscles against it work perform. Because of skeleton "Materials" water one speaks also of one Hydraulic skeleton.

The body wall consists of a non-cellular outer skin, that Cuticula, a einlagigen cell layer, that Epidermis, as interior skin and usually three under it convenient Muscle layers, in Connective tissue are embedded.

The Cuticula is for instance a micrometer thinly, with fine villi occupied and resembles in composition and structure of the Cuticula of the Gliederfuesser. Thus it exists out ?-?-Chitin and various proteins, not however out Kollagen and leaves itself into lying an outside Epicuticula and under it a lying Procuticula are divided, for their part out Exo and Endocuticula builds up. This multilevel structure is for the high flexibility of the outer skin responsible, which makes it for the animals possible, itself still into the closest columns to crimpings. Although it works outward water-repellent, it is not able to prevent humidity losses what has as a consequence that Stummelfuesser can live only in a mikroklima with high humidity.

The surface of the Cuticula is scattered with numerous fine Papillen; the larger of them carry than villi the visible sense bristles. The Papillen is covered for their part with small Schueppchen and lends so to the skin a including-like appearance. It feels during contact also according to drying samtig, for which its water-rejecting nature is responsible. Within the framework by the hormone Ecdyson mediated Haeutung (Ecdysis) it is repelled regularly, sometimes every fourteen days.

It is renewed thereby by the einschichtigen interior skin which was under it, the epidermis, which consists in contrast to the Cuticula of living cells. You are subject a thick layer to connective tissue, which is formed primarily by Kollagenfasern, which are aligned either parallel or perpendicularly to the body longitudinal axis. Within the connective tissue three continuous layers of unspezialisierter smooth musculature lie. The outside, relatively thick layer by the ring muscles, the internal of that likewise voluminoesen longitudinal muscles is formed. Between them are appropriate for thin diagonal muscles, which wind themselves forward and in the back screw-shaped along the body axle. Between ring and diagonal musculature fine blood channels, those exist below the superficially recognizable transverse rings of the skin lie and for these Pseudo segmenting examination mentioned are responsible.

Below the internal muscle layer the body cavity lies. Them become through so mentioned Dorsoventralmuskeln, of the center of the ventral side crosswise by it through to the edges of the back side run, divided in the cross section into three regions: a central center section and two belly-laterally in each case on the left and on the right convenient side parts, which include also the legs.

Haemocoelom and blutkreislauf

The body cavity is a in such a way specified Pseudocoelom, that in the special case also as Haemocoelom one designates. A Pseudocoel is contrary to a genuine Coelom not of a genuine, of embryonalem Mesoderm derived cell layer surround. A Coelom is however trained around the gonads and the elimination serving Nephridien around.

Like the name Haemocoelom already suggest, is filled the body cavity with a blood-like liquid, into which all organs are embedded; in this way they can be supplied easily also in the blood circulating nutrients. This liquid is colorless, since it does not contain pigments; for this reason it serves also only in small measure oxygen transport. In the blood liquid two different types of blood cells or Haemozyten, the Amoebozyten and Nephrozyten move. First have probably a function with the protection from bacteria and other foreign bodies; with some kinds they play a role also with the reproduction. Nephrozyten store against it poison materials or convert them into a form usable for elimination organs the called Nephridien.

The Haemocoelom becomes by a horizontal septum, that Diaphragm, divided into two parts, lain the back pericardialen sine and lain the belly-laterally perivisceralen sine. First surrounds the schlauchfoermige existing ring muscle hose with ever two lateral openings (Ostien) per segment. While it is unknown whether the Hinterende is open or closed, flows it to the front directly into the body concavity. Since it apart from the fine, between the musculature layers of the body wall blood vessels present and a pair and . While the Diastole flows the blood from the pericardialen (heartnear) sine by the Ostien into the heart. As soon as the Systole begins, the Ostien, the heart musculature closes pulls together, reduced so the heart volume and pumps in this way blood from the front end of the heart to the periviscerale (organ near) Haemocoelom. The different fabric with nutrients are supplied in this way there, before the blood finally back-arrives again by the perforations of the diaphragm into the pericardialen sine. Apart from the pumping activity of the heart also body movements have an influence on the blood circulation.

Respiration

Those the animals takes place on the one hand via simple Diffusion over the entire body surface away, with some kinds possibly also over their Coxalvesikel at the stub legs. Most importantly however the gas exchange is over fine normal tubes, those Tracheae, those of the body surface deeply into the body to the different organs, completely particularly however to heart draw.

The wall of these usually less than three micrometers thick structures exists only of an extremely thin Haeutchen, by those that easily to diffuse can. They rise at tiny openings, that Mirror-image blades, those for their part in each case to several in a dellenfoermigen recessing of the outer skin, that Atrium, are summarized. The number of the in such a way developing trachea bundles can be indicated as on the average 75 for each to body segment; accumulated up they arise particularly on the back of the animals.

Differently than Gliederfuesser, which can control their trachea openings, the Stummelfuesser is not in addition able. Their tracheae are always opened, which entails large losses of water with dryness. For this reason Stummelfuesser are on habitats with higher dependent.

Digesting system

The digestive tract begins with that subterminal, something behind the foremost point of the body on the ventral side mouth lain, in booty by the Kiefer occupied with fine denticles mechanically to be thus cut up can. Two salivary glands flow themselves by a common leader into the following throat, which already represents the first part of the front intestine. Of them produced Saliva Schleim contains and hydrolytic becomes by selective Recuperation from nutrients and water as well as by isolation of poison and waste materials in the Nephridiodukt still in his composition changes, before it is transferred to the Nephridiopore to the external world. The most important elimination product is the water-insoluble Urine acid; it can be transferred in solid state with only little water to the environment. This as uricotelisch designated elimination mode represents an adjustment to the land life and the necessity to deal economically with water.

A former Nephridienpaar in the head was converted secondarily into the salivary glands, a further in the last segment of the males takes over today a gland function, which is apparent used with the reproduction.

Nervous system

The nervous system consists primarily of that und zwei bauchseitigen Nervensträngen, die durch zahlreiche Querverbindungen miteinander verbunden sind, so dass man auch von einem „Strickleiternervensystem“ spricht.

That convenient brain consists in front and back of a left and a right half, which form a ring together with nerve connections around the esophagus. A three-division of the brain toward the body longitudinal axis, as one it with the closely used Gliederfuessern (Arthropoda) finds, can only in the embryonalen condition be observed.

From the brain about fifteen pairs of nerves proceed, both the sensory, and motor . The main nerves of the head area are the optical nerves, the eyes and brain connect and two sensory nerves, which pull to chemical attractions into the antennas and are responsible for the switching of contact and. The most important body nerves are against it two far apart lying, belly-lateral nerve strands, which pull themselves the entire body along lengthwise-laterally to the rear. Per segment is one pair each of inconspicuous nerve cell concentrations, those Ganglia, which are connected by nine or ten transverse nerves in each case. Body wall and attaches by mixed nerves is supplied, which both sensory, the reflecting perception serving and motor, muscles the responding signals to pass on.

Sensory organs

The entire body including the stub feet is uebersaeht with numerous Papillen, warzigen projections/leads, some on mechanical attractions responding (mechanorezeptive) bristle at the point carry, which is connected also in each case far sensory nerve cells lying inside. Also the Mundpapillen, the exits of the Schleimdruesen, has probably a function with the sensory perception.

On the "lips", the Labrum, convenient sensory cells or Sensillen it serves against it the perception of chemical attractions why one of Chemoreceptors speaks. They are also on the two antennas, which can be regarded as the most important sensory organs of the Stummelfuesser.

With exception of some fewer, usually excavate-living kinds one simply built each is at the beginning of the antennas (Ocellus), from a chitinhaltigen as well as Cornea/callosity and exists and by ever an optical nerve is connected with the brain. The retina consists of numerous pigment cells and photorezeptoren; with the latters it acts over easily modified itself Scourge cells, whose carries scourge diaphragm an photo-sensitive pigment on the surface.

Reproduction organs

Both sexes have gonads in pairs, through as Gonodukte designated implementing courses into common genital aperture, those Gonopore, flow, which is on the rear ventral side. Both gonads and Gonodukte lead themselves from genuine Coelomgewebe off.

With the females the two ovaries in the center grew together and to the horizontal running septum attached. The Gonodukte is differently pronounced, according to whether it concerns living-bearing or egg-laying kinds. With first each implementing course divides into a slim eileiter and a roomy "gebaermutter", that Uterus, in which the embryos grow up. The unique Vagina, with which both Uteri are connected, flows to the Gonopore outward. With egg-laying kinds, whose Gonodukte is homogeneously developed, those is to genital aperture because of the point of a long laying eggs apparatus, of the Ovipositors. The females of many kinds order in addition over a seed memory, in which sperm cells of the males can be kept passing or also at longer term.

Males have two separated Testicle as well as the pertinent Seed vesicle (vesicula seminalis) and implementing courses (vasa efferentia). The latters unite to a common samenleiter, that vas deferens, itself again to Ejakulationsleiter widened to the Gonopore outward opens. Directly beside and/or behind this are appropriate with the males two for pair of special glands, which have probably an auxiliary function with the reproduction; the glands of the rear pair are called also Analdruesen.

One structure could so far only with males of the kind Paraperipatus to be proven, but yet in action not be observed. Males of numerous Australian kinds exhibit against it as previously mentioned special structures at the head, which apparent take over tasks during the seed transmission on the females.

Spreading and habitat

Spreading of the Onychophora: Peripatidae (green), Peripatopsidae (blue)

Stummelfuesser live in tropical habitats and in the moderate zone of the Southern Hemisphere; they point both one zirkumtropische, and one zirkumaustrale Spreading up. One finds individual kinds in and , Indonesia and parts . The whole of the today's circulation areas points to the probable origin of the on the former supercontinent Gondwana , why one speaks also of a Gondwana distribution.

All Stummelfuesser is landliving (terrestrial) and dark habitats with high air humidity prefer. For it in particular the rain forests of the Tropics and moderate zones are applicable, where itself the animals in liquid, which is produced by the two Schleimdruesen, in order to make their victims immovable. It is sprayed by the pores of the Mundpapillen over a distance of up to 30 centimeters and hardens at air very fast out, so that the booty gets caught in the strongly sticky substance and becomes immovable finally. On the water-rejecting skin of the Stummelfuesser the substance does not stick against it so that the animals can approach their victim safely on shortest distance. It is now killed and before-digested by injection of toxic saliva; the sharp Kiefer cuts the booty then into fine pieces, which arrive over the mouth into the digestive tract.

The predatory way of life is probably a result of the high dampness needyness of the organisms: Because of the steady drainage danger often only few hours are available on the day for food procurement, so that a strong Selection for a low cost-benefit ratio exists, which can hardly be reached by a vegetable nutrition.

Fressfeinde and parasite

Important Fressfeinde of the animals is primarily various Spiders (Araneae) and Hundertfuesser (Chilopoda), besides in addition, (Rodentia) and Birds, in central America about those Gilbdrossel (Turdus grayi). To that Korallenottern (Micrurus) counted kind of queue Micrurus hemprichii even almost exclusively nourishes itself of Stummelfuessern. For the defense some kinds roll themselves reflex-like to a spiral together; besides the animals can set themselves also by Schleimauswurf against smaller opponents to the resistance.

Various one (Acari) are as Ectoparasiten admits, which settle on the skin of the Stummelfuesser. With skin injuries it comes besides usually that Peripatopsidae, frequently in regions with unsteady food offer or changeful climate. Those about 1.3 to 2 millimeters large, strongly dotterhaltigen eggs are coated in this case of a protecting egg shell from chitin; muetterliche welfare service is unknown.

  • The majority of the kinds is egg-living-bearing: The medium sized, only eggs coated by a diaphragm remain to the Uterus, those in the "gebaermutter", Embryo nourish themselves however of the moderate quantity Dotter, which are contained in the eggs and separately supplied by the nut/mother, one designate it therefore also as lecitotroph; they slip only briefly before the birth. Probably this represents the original reproduction mode of the Stummelfuesser, i.e. both ovipare and vivipare kinds developed from the ovoviviparen forms.
  • Genuinly living-bearing kinds are in both families, particularly in regions with a climate and an even food offer stable over the year. The embryos developing from the only mikrometergrossen eggs are nourished in the Uterus by their nut/mother; they become therefore as matrotroph designated. The supply takes place either via muetterliche secretion delivery into the Uterus or via a genuine fabric connection between the bearing nut/mother epithelium and the growing up embryo, a in such a way specified Plazenta. First occurs only outside of the American continent, the latter is primarily in America and that : In a there forest district its own "velvet is used worm conservation flat", which is particularly cut to a Stummelfuesser kind.

    To be bred Stummelfuesser cannot so far yet. Appropriate considerations exist however, not only with that ulterior motives to be able to make populations available for later Auswilderungen but also, in order to clear the public up concerned better over the animals and the necessity for their protection. Due to the often multicolored colors and the great importance for evolution history an attitude would be applicable into "insect zoos" for example.

    Master history

    Modern forms

    Under the today's forms the Stummelfuesser is probably very closely related to the Gliederfuessern (Arthropoda), a very extensive (Insecta) and (Arachnida) counts. With them they divide among other things the skinned and from?-?-Chitin as well as not nicht-kollagenen proteins compound external skeleton, the gonads and elimination organs, the open Blutsystem with back convenient hose heart, a body cave divided into pericardiale and periviscerale caves, respiration, surrounded by genuine Coelomgewebe, by tracheae and a similar Embryonalentwicklung. In addition segmenting with two appendices of body each per segment comes. Antennas, Mandibeln and Oralpapillen are probably not homologous to the appropriate parts of the body of the Gliederfuesser against it, i.e., they developed probably independently of these.

    A further closely used group are relative those generic term cures (Tardigrada), which however due to its very small size of a set of characteristics the stub and Gliederfuesser are missing such as blutkreislauf and separate breathing structures. Imagine together Stummelfuesser, Gliederfuesser and Baertierchen Taxon, the Panarthropoda, i.e., all three groups collected cover all descendants of their last common moving forward.

    Within the Panarthropoda the Stummelfuesser was usually combined due to a certain form relationship with the Baertierchen into a Taxon Protoarthropoda. With this designation it should be expressed that both, Stummelfuesser and Baertierchen, not yet the full development height of the Gliederfuesser to have reached. Modern systematic theories reject such conceptions of "primitive" and "highly developed" ways of life and orient themselves instead exclusive at the masterhistorical verwandtschaftsverhaeltnissen of the Taxa involved. These are not enlightened yet to the Gaenze; it is considered however as relatively probable that the group of sisters of the Stummelfuesser is formed by a Taxon, which is covered both Baertierchen and Gliederfuesser and and designated Tactopoda: 

    Panarthropoda
| -- Stummelfuesser
| -- Tactopoda
   | -- Baertierchen (Tardigrada)
   | -- Gliederfuesser (Arthropoda)

    Into the further relationship of the Stummelfuesser long time became those Ringelwuermer (Annelida) posed. With them it connects among other things the worm-like body, the thin and flexible outer skin, a schichtige musculature, elimination organs in pairs put on as well as a simply built brain and simple eyes. Decisive was however segmenting existing at both groups, which shows little specialization of the segments only. Those Parapodien appendices of body mentioned of the Ringelwuermer therefore correspond to the member masses of the Stummelfuesser.

    In of Georges Cuvier coined/shaped ArticulataThe Stummelfuesser applies for concept therefore as evolutionary link between Ringelwuermern and Gliederfuessern: Worm-well-behaved forerunners developed therefore first Parapodien, which developed themselves further then over stub legs as link in the long run to the appendices of body of the Gliederfuesser. The Stummelfuesser was considered due to its structural Konservatismus therefore as living fossils. This opinion comes paradigmatisch in the statement of the French zoologist A. Vandel to the expression:

    Onychophorans CAN considered highly evolved annelids, adapted tons terrestrial life, which announced prophetically the Arthropoda. They of acres A laterally branch which has endured from ancient times until today, without important modifications.
    Onychophoren can be regarded as highly developed and to the land life adapted Ringelwuermer, which announced prophetisch the appearance of the Gliederfuesser. They are a seitenast, which outlasted without relevant changes from primeval times until today.1

    Modern systematics strive to leave criteria like a "more higher" or "lower" entwicklungsstufe of the regarded organisms just as outside before as distinctions in main and seitenaeste - you apply only due to methodology opened family relations as material. For the Articulata concept speak from this view still concerned the body, the presence of paired appendices of segment, segmented at all groups of animals, the plant in pairs of elimination organs in each segment and above all a cord leader-like developed nervous system on the basis of a double nerve strand lain belly-laterally.

    The representatives of an alternative and today by the majority preferential concept, the Ecdysozoa hypothesis in such a way specified, place against it Ringelwuermer and Panarthropoda in two very different large's groups, those Lophotrochozoen (Lophotrochozoa) on the one hand and those Haeutungstiere (Ecdysozoa) on the other hand.

    They assume with the fact it itself with the aforementioned thing in common of Ringelwuermern and Stummelfuessern either over convergently developed or around "primitive" characteristics, so mentioned (Nematomorpha) also three rather obskure groups, Hakenruessler (Kinorhyncha), Priapswuermer (Priapulida) and (Loricifera) counts. 

     (Protostomia)
| -- Haeutungstiere (Ecdysozoa)
| | -- Panarthropoda (Gliederfuesser, Stummelfuesser, Baertierchen)
| | -- Cycloneuralia (thread worms, string worms and further)
| -- Lophotrochozoen (Lophotrochozoa) (Ringelwuermer, soft animal and further)
| -- further

    Particularly characteristically of the Cycloneuralia is more lain about around the mouth opening, more zirkumoraler, nerve ring, that the proponents of the Ecdysozoa concept in modified form also in the inside four-sample, thus the details of the nerve arrangement, which Panarthropoda recognize. In addition come all groups more together Haeutungsmechanismus, those Ecdysis, and molecular-biologically found thing in common. A problem of the Ecdysozoa hypothesis is those subterminale Mouth position of the Stummelfuesser: Differently than with the Cycloneuralia the mouth is not at the front end of the body, but lies belly-laterally behind it. There are however by development-biological investigations, in particular regarding the emergence of the head nerves, references on the fact that this was not always the case and the mouth originally terminal, thus was finalconstantly put on. This is supported by the fossil findings.

    Become extinct forms

    The fossil excessive quantity of the Stummelfuesser closes Fossils from three different time periods, in particular the early epochs of the Earth antiquity Kambrium and Ordovizium, the later as well as that Tertiarily in that Neozoic era. The kambrischen and ordovizischen forms, whose affiliation to the Stummelfuessern is disputed, lived still all together in the sea, while the later kinds apply already than terrestrial.

    All fossil forms become traditional into a separate Xenusia posed, while the modern are called Euonychophora. This classification states however nothing over the actual masterhistorical connections, why it working Taxonomen is not accepted.

    Lobopoden

    The oldest approximately completely received fossils originate from the lower kambrium. The most remarkable characteristics, the this as Lobopoden if designated forms with the modern Stummelfuessern divide, are the worm-like body form and the numerous stub legs. A characteristic of many Lobopoden are against it numerous armour-plates, those Scleriten, which cover often back the whole body with the head; since they are enough in, pointedly approaching back pricks run out, had them in all probability a defensive function to the protection from Fressfeinden. Individual Scleriten can be proven as a component "small shelly of the fauna in such a way specified" (SSF) before incipient crack of the kambriums 543 million years ago - therefore the Lobopoden and/or its direct ancestors has themselves already in the epoch of the Ediacarium of the Proterozoikums developed and were thus the first animals running on legs.

    Among the more well-known kinds one ranks about Aysheaia, from the Canadian Burgess slate admits is and from all Lobopoden the modern Stummelfuessern sees most similar - a pair of appendices of head can be interpreted as forerunners of the antennas. Xenusion apparent was able to together-roll itself with the pricks outward which permits views of the defense strategy of the Lobopoden. The by far most famous Lobopoden kind is however Hallucigenia. It received from the paleontologist Simon Conway Morris due to its bizarren appearance their scientific name. Reconstructed by it with long, stelzenfoermigen legs and puzzling fleshy back excrescences, it was considered for a long time as prime example for the fact that nature in the kambrium experimented with the most diverse and bizarrsten figure plans. It showed up however by further finds that the reconstruction had exchanged above and down; by interpretation of the "stelzen" as back pricks it became clear that the fleshy excrescences on the back were in reality legs. The second reconstruction exchanged however for their part front and rear side of the animal; only after further investigations it turned out that Conway Morris had correctly oriented the fossils in this regard.

    Lobopoden fossils are today in North America, China and north and/or northeast Europe. The discovery sites lay in the kambrium due to that however substantially far south in the tropical and moderate belt of the earth and corresponded to at that time flat lagoon waters.

    The way of life of the Lobopoden lies to a large extent in the dark, some kinds apparent nourished itself carnivor, thus different animals ate as for instance Sponges (Porifera) or sea-roll-similar Stachelhaeuter (Holothuroidea) of the kind Eldonia. The fact that they haeuteten themselves like modern Stummelfuesser is considered as proven.

    If they still placed a considerable portion of the diversity of species in the kambrium, this reduced drastically in the Ordovizium; at the latest with the incipient crack of the Silurs applies the Lobopoden strictly speaking than become extinct. The US-American paleontologist this sees as symptom of a wide collapse of the diversity of species of the kambriums, which announced an end of the "experimentation phase", its theses is however considered as disputed.

    Lobopoden are brought traditionally due to the very similar morphology with the Stummelfuessern in connection; in this opinion they were main line representatives of this Taxons: 

    Stummelfuesser (Onychophora, alternatively: Lobopodia)
|==diverse Lobopoden kinds (sea-living, paraphyletisch)
| -- Udeonychophora (alternative: Onychophora) (landliving, modern and fossil kinds cover)

    Occasionally the scientific name Onychophora designates only the landliving forms, while the larger group, which includes also the different Lobopoden then as Lobopodia is designated.

    An important alternative view assumes the Lobopoden instead main line representatives of the Panarthropoda and Tactopoda were: 

    Panarthropoda
| - -Aysheaia
|-n. N.
   | -- Stummelfuesser (Onychophora) of inclusive become extinct landliving kinds
   |-n. N.
      |==diverse Lobopoden kinds (paraphyletisch)
      | -- Tactopoda (Baertierchen + Gliederfuesser)

    The kind Aysheaia, which agrees in particularly many characteristics with the modern Stummelfuessern, forms therefore the group of sisters of all other Panarthropoda, which divide themselves then in the Stummelfuesser and all remaining forms. The remaining Lobopoden kinds are considered now as representatives of that line of development, which leads to the modern Baertierchen and Gliederfuessern. From that analysis can be determined then a trend to intensified outside segmenting and to a tuning of the fine body and leg struggle on the situation of the segment borders.

    The result can be agreed however only heavily with the Articulata hypothesis, because it means that pronounced segmenting of Ringelwuermern and Gliederfuessern must have developed independently. For the Stummelfuesser this would be called that that Are missing an original, "primitive" and no secondary characteristic to a clearly recognizable outward segmenting represents. The second hypothesis for the systematic position of the Lobopoden gets along therefore by far better with the above Ecdysozoa concept.

    Landliving forms

    Four terrestrial forms of the Stummelfuesser are well-known, with which there is no large doubt contrary to the Lobopoden about the systematic position.

    When the transition carried out itself ashore, is unknown; as plausible it is considered that it between Ordovizium and late Silur, thus before approximately 490 to 420 million years, in that Tidal zone took place. Typical armoring of the Lobopoden could have been lost, if it were present ever with the ancestors of the modern kinds, at this time to be able to move perhaps in order through the won flexibility better in close habitats. In the tidal zone also the different adjustments could have developed to the land life, for instance the tracheae, therefore independently of those of the insects would have developed or the internal fertilization mode, which makes a transmission of the sperm cells possible into a life-friendly environment also with wassermangel. Over the time of re-designing the Nephridien in saliva and genital auxiliary glands can be only speculated; with the Schleimdruesen used to the booty catch it is nevertheless well-known that they are nonfunctioning under water, from which carefully can be closed that they were probably only formed ashore, perhaps originally for the defense by Fressfeinden.

    Where always the transition took place in the long run, it was apparent no the fossil formation favouring environment; anyhow not one fossil exists from this early period. From the tropical belt of the late kind admitted Helenodora inopinata was very probably already landliving and differs only little from the modern forms. From this reason and the still large similarity to Lobopoden how Aysheaia are considered Stummelfuesser as prime example to evolutionary State security service and one bradytelische Evolution rate, with which the biological organization of the total organism changes itself only very slowly, because strong stabilizing the entire line of development in a close passage of the morphologic-anatomical "area" limits and larger deviations from the "typical" Stummelfuesserform not tolerated.

    From that only one fossil is well-known, those chalk-temporal Kind Cretoperipatus burmiticus, in from the Southeast Asiatic one found and on an age by 100 million years one dates. It can do even already one of the modern families, that Peripatidae, to be assigned.

    Since today's Stummelfuesser exhibits a Gondwana distribution in such a way specified, much speaks for the fact that their move forward lastly more together on evenly this Urkontinent lived. The fact that also outside of Gondwanas or the today's remnants of this continent landliving Stummelfuesser existed proves the existence of Succinipatopsis balticus, 44 million a years old kind, itself in from the period of the lower received. The circulation area of the Stummelfuesser must have been substantially larger thus once than today - when and for what reason all not Gondwana kinds became extinct, is unknown.

    The fourth fossil kind is Tertiapatus dominicanus, those from amber of the Karibik island admits is. It is possible, but not provable that it already one of the two modern families, which Peripatidae belonged. The kind can be dated on an age from 17 to 20 million years.

    By both fossil ones of the Tertiary period show themselves clearly the Schleimdruesen, which thus at the latest at this time, probably however to have already substantially in former times developed to have itself. Formally the two tertiary forms in a Taxon Tertiapatoidea are summarized, which represents however probably only one figuration axon.

    Systematics

    The modern Stummelfuesser forms a in such a way specified , thus all descendants of their common moving forward cover group. Important common derived characteristics (Synapomorphien) the Kieferwerkzeuge (Mandibeln) second is and the Mundpapillen with associated Schleimdruesen of the third body segment, belly-laterally running nerve strands with numerous cross connections per segment and the special form that for example Tracheae.

    Until 2004 became about 155 modern kinds described, which are assigned 47 kinds; the actual kind number is however probably about twice as large. The type kind is most well-known Peripatus, which was already described 1825 and in the English-language area also on behalf for all Stummelfuesser is located.

    All kinds become one of two assigned, their circulation areas do not overlap, but are by arid areas or seas from each other separated.

    • Those Peripatopsidae exhibit relatively many as original or "primitive" estimated characteristics. They possess 13 to 25 pairs of legs; behind or between the last of it is the genital aperture (Gonopore). Both egg-laying (ovipare), egg-living-bearing (ovovivipare) and genuinly living-bearing (vivipare) kinds do not occur, a Plazenta possess Peripatopsidae however in principle. Their circulation area lies zirkumaustral in Australia and Tasmanien, New Zealand, new Guinea, South Africa and Chile.
    • Those Peripatidae show a set of derived characteristics. From larger durchschnittslaenge than the Peripatopsidae they also more pairs of legs possess: Their number varies within the group between 22 and 43; the Gonopore always lies between the next to last of it. Ovipare kinds does not give it with the Peripatidae, the by far outweighing number is vivipar. With many females of the latter group a Plazenta is formed, which supplies the growing up embryo with nutrients. Occur the Peripatidae are limited to the tropical and subtropical zone; in detail they occur in central and in the northern South America as well as on several Caribbean islands, besides also in west Africa, north India, Malaysia and individual Indonesian islands.

    Literature

    • H. Resting mountain: Onychophora, Stummelfuesser, in west heath W, Rieger R: Special Zoologie, part of 1: Single-celled organism and eddy lots of animals, spectrum academic publishing house Heidelberg 1996
    • E. E. Ruppert, R. S. Fox, R. D. Barnes, Invertebrate Zoology: A functional evolutionary approach, 7th OD., Brooks/Cole, 2004, chapter 15, page 505, ISBN 0-03-025982-7
    • R. C. Brusca, G. J. Brusca, Invertebrates, 2nd OD., Sinauer Associates, 2003, chapter 15, page 463, ISBN 0878930973

    Scientific literature

    • G. E. Budd, The morphology OF Opabinia regalis and the reconstruction OF the arthropod stem group, Lethaia, 29, 1996, page 1
    • J. Eriksson, Evolution and development OF the Onychophoran Head and Nervous system, Comprehensive Summary OF Uppsala thesis from the Faculty OF Science and Technology 833, 2003
    • X. Hou, J. Mountain-flow, Cambrian lobopodians - ancestors OF extant onychophorans, Zoological journal OF the Linnean Society, 114, 1995, page 3
    • J. Monge Najera, Phylogeny, biogeography and reproductive trends into the onychophora, Zoological journal OF the Linnean Society, 114, 1995, page 21
    • T. R. New one, Onychophora into invertebrate conservation: priorities, practice and prospects, Zoological journal OF the Linnean Society, 114, 1995, page 77
    • G. Poinar, Fossil onychophorans from Dominican and Baltic Amber: Tertiapatus dominicanus n.g., n.FR. (Tertiapatidae n. fam.) and Succinipatopsis balticus n.g., n. FR. (Succinipatopsidae n. fam.) with A proposed classification OF the subphylum Onychophora., Invertebrate Biology, 119, 2000, page 104
    • G. Poinar, Fossil velvet Worms in Baltic and Dominican Amber: Onchychophoran evolution and Biogeography, Science, 273, 1996, page 1370
    • C. J. Wedeen, R. G. Kostriken, D. Leach, P. Whitington, Segmentally iterated expression OF on engrailed class genes into the embryos OF at Australian onychophoran, development of gene and evolution, 207 (4), 1997, page 282

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