Die Cheliceren der Araneae,Amblypygi und Uropygi mit den Skleriten,den Plagulae (Chelicerata,Arachnomorpha)

Zusammenfassung 1. Die Arachnomorpha — Uropygi, Amblypygi, Araneae — besitzen in den Cheliceren ein oder zwei Sklerite an der Basis der Klaue, die Plagula ventralis und die Plagula dorsalis. Diese sind Bildungen der Haut und werden mit der Exuvie abgeworfen.2. Die Plagula ventralis ist im allgemeinen ein plattenförmiger oder stäbchenförmiger Sklerit. Proximal setzen an ihr die Beugemuskeln für die Klaue an. Distal ist sie durch ein biegsames Stück mit der Klaue verbunden. Da die Plagula ventralis vor dem Gelenk der Klaue ansetzt, verlängert sie den Hebelarm für die Beugemuskeln.3. Die Plagula ventralis ist im allgemeinen einfach, sie ist weiter entwickelt bei den Mygalomorphae der Araneae. Außen ist sie von einer dünnen Schicht Epicuticula begrenzt, darunter folgen dickere Schichten von Exo- und Mesocuticula. Der biegsame Teil am Ansatz der Klaue besteht nur aus Mesocuticula unter der dünnen Epicuticula.4. Die Plagula dorsalis findet sich nur bei Mygalomorphae der Araneae. Nur die Masteriinae besitzen sie nicht. Die Plagula dorsalis liegt als ein schmales Band quer vor der Basis der Klaue im dorsalen Fenster. Sie ist an drei Stellen verdickt und hier von feinen Kanälen durchzogen. Proximal und distal setzen die Sehnen der Streckmuskeln für die Klaue an. Eine besondere Funktion konnte nicht ermittelt werden.5. Die Nahrungsaufnahme, Kauen oder Saugen, ist an der Struktur der Cheliceren zu erkennen. Kauer besitzen zwei Reihen von Zähnen, manchmal in großer Anzahl. An der Basis des Grundgliedes befindet sich außen ein großer Condylus als Führungsschiene. Bei den Saugern ist die Anzahl der Zähne manchmal bis auf einen reduziert. Der Condylus an der Basis des Grundgliedes fehlt oder ist nur als Vestigium vorhanden.6. Die Plagula ventralis ist eine Autapomorphie des Taxon Arachnomorpha. Die Plagula dorsalis ist eine Autapomorphie der Mygalomorphae innerhalb der Araneae.

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The plagulae, sclerites at the base of the chelicerae of Araneae, Amblypygi, and Uropygi (Chelicerata, Arachnomorpha)

Summary 1. The Arachnomorpha (Uropygi, Amblypygi, Araneae) have one or two sclerites at the base of the fangs of their chelicerae, here called plagula ventralis and plagula dorsalis. These sclerites are part of the exoskeleton and are thus also visible in exuviae.2. Generally, the plagula ventralis is a plate- or rod-shaped sclerite, with the fang flexor muscles attached at its proximal end. Distally it is connected to the fang by a flexible part. Being attached distad of the fang articulation, the plagula ventralis extends the leverage of the flexor muscles. The plagula ventralis is simple in most Arachnomorpha, but in Mygalomorphae (Araneae) it is more complicated. Externally there is a thin epicuticular layer, with thicker layers of exo- and mesocuticula underneath. The flexible part at its contact with the fang consists exclusively of mesocuticula.3. The plagula dorsalis is found only in Mygalomorphae. It forms a narrow strip across the dorsal base of the fang. Three sections of it are thicker and passed by thin channels, with tendons of the fang extensor muscles attached to their proximal and distal ends. The function of the plagula dorsalis remains uncertain.4. The presence of a plagula ventralis is an autapomorphy of the Arachnomorpha, whereas the plagulae dorsalis are hypothesized to be an autapomorphy of the Mygalomorphae within the Araneae.5. Different modes of food ingestion (chewing and sucking) may be recognized by different cheliceral structures. Chewers have numerous teeth; outside at the base of the paturon a big condylus acts as a leading strip. Those that pump insects out have fewer teeth, in several cases only one tooth. The condylus at the base of the paturon is missing or vestigial.

     

Larvenentwicklung und Metamorphose von Pycnogonum litorale (Chelicerata,Pantopoda)

Zusammenfassung Es werden Haltungsmethoden beschrieben, die es ermöglichen, Pycnogonum litorale kontinuierlich im Labor zu züchten. Die Larven leben ectoparasitisch an dem Hydroidpolypen Clava multicornis (Coelenterata, Hydrozoa). Sie durchlaufen bis zur Vollendung der juvenilen Form 6 Häutungen. Das erste Stadium ist das Protonymphonstadium. Bei der ersten Häutung gehen die für dieses Stadium typischen Haftorgane, die langen Spinndorne der Cheliphoren und die Borsten der Terminalklauen verloren. Bei der zweiten Häutung tritt am caudalen Larvenende eine dreizipfelige Wachstumszone auf. Bei der 3. bis 6. Häutung wird zusätzlich zu den drei larvalen Extremitätenpaaren im Sinne einer Anamerie jeweils am Körperende ein weiteres Segment mit einem definitiven Laufbeinpaar neu gebildet.Bei der 5. Häutung wird der vordere larvale Körperabschnitt mit den drei Paar Larvenextremitäten und dem Larvenrüssel zurückgebildet. Es entsteht der viel größere, definitive Rüssel. Diese Umwandlung ist funktionell mit dem gleichzeitig erfolgenden Wirtswechsel von Clava multicornis auf Metridium senile (Coelenterata, Anthozoa) verbunden. Sie ist der entscheidende Schritt der Metamorphose der Larve zum juvenilen Stadium. Ihr folgt nur noch das Auswachsen des vierten definitiven Beinpaares bei der 6. Häutung.Die Larven werden rasterelektronenmikroskopisch untersucht. Ihre Extremitäten, der Rüssel und Feinstrukturen der Cuticula wie Borsten, Spinndorne, Drüsenporen und Dorsalhöcker werden beschrieben. Borstentragende Klauen und Spinndorne werden funktionell gedeutet. Sie dienen der Anheftung an das Wirtstier.Die frisch aus dem Ei geschlüpften Larven sind 0,15 mm, die sechsbeinigen Tiere beim Wirtswechsel nach der 5. Häutung ca. 1 mm lang. Die ersten 5 Häutungsintervalle, also bis zum Verlust der Larvalorgane, dauern unter Laborbedingungen bei 15° C minimal 67 Tage, im Mittel 83 Tage.

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Larval development and metamorphosis of Pycnogonum litorale (Chelicerata, Pantopoda)

Summary Techniques are described for the continuous rearing of the pycnogonid Pycnogonum litorale in the laboratory. The larvae feed as ectoparasites on a polyp, Clava multicornis (Coelenterata, Hydrozoa). From hatching from the egg up to the stage with the definite body shape six moults occur. The first larval stage is the protonymphon. At the first moult it looses adhesive structures typical for this stage. After the second moult three swollen appendices become obvious at the posterior part of the larval body, indicating a region of predominant growth. At each of the four subsequent moults a new segment with one pair of definitive legs each is established by an anamery in addition to the three pairs of preliminary larval extremities. However, at the fifth moult the three pairs of larval legs and the larval proboscis vanish. A much bigger definitive proboscis is established. At the same time the animal changes its host and subsequently feeds on Metridium senile (Coelenterata, Anthozoa).This moult is the main step in the metamorphosis of the larva to the juvenile stage. It is only completed by the growth of one more pair of definitive legs at the sixth moult. The larval stages are described with special regard to the extremities, the proboscis, and fine structures of the cuticle like bristles, spinning- and other gland associated structures, and dorsal humps using scanning electron microscopy. Bristled claws and prickles are explained to have adhesive functions.Newly hatched larvae have a body length of 0.15 mm and grow up to about 1 mm after the fifth moult (change of the host). Under laboratory conditions at 15° C the larval development from hatching to the fifth moult (time point for losing larval extremities and proboscis) takes 67 days in minimum and 83 days in average..

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Abkürzungen b Basalglied der Cheliphoren - ch Cheliphoren (synonym p1) - p1 erstes Paar Larvenextremitäten (synonym Cheliphoren) - p2 zweites Paar Larvenextremitäten - p3 drittes Paar Larvenextremitäten - p4 bei der 3. Häutung erworbenes Extremitätenpaar - p5 bei der 4. Häutung erworbenes Extremitätenpaar - p6 bei der 5. Häutung erworbenes Extremitätenpaar - p7 bei der 6. Häutung erworbenes Extremitätenpaar definitive Laufbeine - r Rüssel - sb beweglicher Scherenfinger der Cheliphoren - su unbeweglicher Scherenfinger der Cheliphoren - sp Spinndorn Mit Unterstützung der Deutschen Forschungsgemeinschaft SFB 87, Projekt A1, D. BückmannTeil der Dissertation von W. Behrens, Universität Ulm     

Lebenszyklus und postembryonale entwicklung der geibelspinne Tarantula marginemaculata C. L. Koch (Chelicerata,Amblypygi) im laboratorium

In the laboratory, Tarantula marginemaculata breeds during the summer months. Egg development takes 98 days. Development from hatching to maturity takes 8 to 10 months and involves 5 to 8 moults. Mature animals continue to moult and to grow and normally produce 1 to 2 broods per year. Moulting frequency, growth, development of sexual organs and of trichobothriotaxy, and regeneration are described and compared to those of other arachnids.

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Lebenszyklus und postembryonale entwicklung der geibelspinne Tarantula marginemaculata C. L. Koch (Chelicerata, Amblypygi) im laboratorium

     

Ein atlas der spaltsinnesorgane von Cupiennius salei keys. Chelicerata (Araneae)

To facilitate further physiological investigation, a survey was undertaken of all the slit sense organs to be found on the body of the spider Cupiennius salei. We counted and mapped more than 3 000 sensory slits in the cuticle about half of which are combined to small groups of up to 29 slits forming compound or lyriform organs.     

Double spermatogenesis in Chelicerata

Sperm dimorphism is a rare phenomenon in Chelicerata. Until now, it was known only from three species of the opilionid genus Siro (Sironidae, Cyphophthalmi). Fertilizing (eusperm) and nonfertilizing spermatozoa (parasperm) develop in the same cyst and are thus sister cells. The fine structure of the spermatozoa of two species has been examined and is compared here. In contrast to Siro rubens, S. duricorius spermatozoa lack an acrosomal complex. Both sperm types produce a transitional process, a more or less modified flagellum, which is later retracted. Hence, the spermatozoa are aflagellate. Eusperm and parasperm of all three species form highly ordered sperm balls that are stored in the deferent duct. Reviewing and adding new results about the sperm dimorphism in this arachnid taxon provides the basis for some considerations of another enigmatic morphological character found in Uropygi and Amblypygi, i.e., the tubular accessory genital glands that show holocrine extrusion. These glands are suggested to represent modified, infertile derivatives of the testis anlage. Their secretion is produced in a way reminiscent of a strongly degenerated spermatogenesis. Consequently, these products may be regarded as strongly degenerated germ cells representing a line of germ cell development, which has been separated very early in spermatogenesis from the usual line leading to fertilizing sperm cells. This further, although less evident, case of probable dichotomous germ cell development is discussed with respect to the controversial phylogenetic-systematic relationships between Uropygi (Thelyphonida and Schizomida), Amblypygi, and Araneae.     

Zum feinbau der cuticula von Limulus polyphemus L. (Chelicerata,Xiphosura)

The surface structure of the fracture in the exuvia of Limulus caused by the shedding of the exoskeleton is compared with the fine-structure of experimentally induced fractures using the electron microscope, Stereoscan.     

Geological history and phylogeny of Chelicerata

Chelicerata probably appeared during the Cambrian period. Their precise origins remain unclear, but may lie among the so-called great appendage arthropods. By the late Cambrian there is evidence for both Pycnogonida and Euchelicerata. Relationships between the principal euchelicerate lineages are unresolved, but Xiphosura, Eurypterida and Chasmataspidida (the last two extinct), are all known as body fossils from the Ordovician. The fourth group, Arachnida, was found monophyletic in most recent studies. Arachnids are known unequivocally from the Silurian (a putative Ordovician mite remains controversial), and the balance of evidence favours a common, terrestrial ancestor. Recent work recognises four principal arachnid clades: Stethostomata, Haplocnemata, Acaromorpha and Pantetrapulmonata, of which the pantetrapulmonates (spiders and their relatives) are probably the most robust grouping. Stethostomata includes Scorpiones (Silurian–Recent) and Opiliones (Devonian–Recent), while Haplocnemata includes Pseudoscorpiones (Devonian–Recent) and Solifugae (Carboniferous–Recent). Recent works increasingly favour diphyletic mite origins, whereby Acaromorpha comprises Actinotrichida (Devonian–Recent), Anactinotrichida (Cretaceous–Recent) and Ricinulei (Carboniferous–Recent). The positions of the Phalangiotarbida (Devonian–Permian) and Palpigradi (Neogene–Recent) are poorly resolved. Finally, Pantetrapulmonata includes the following groups (listed here in their most widely recovered phylogenetic sequence): Trigonotarbida (Silurian–Permian), Uraraneida (Devonian–Permian), Araneae (Carboniferous–Recent), Haptopoda (Carboniferous), Amblypygi (?Devonian–Recent), Thelyphonida (Carboniferous–Recent) and Schizomida (Paleogene–Recent).     

Segmentation and tagmosis in Chelicerata

Patterns of segmentation and tagmosis are reviewed for Chelicerata. Depending on the outgroup, chelicerate origins are either among taxa with an anterior tagma of six somites, or taxa in which the appendages of somite I became increasingly raptorial. All Chelicerata have appendage I as a chelate or clasp-knife chelicera. The basic trend has obviously been to consolidate food-gathering and walking limbs as a prosoma and respiratory appendages on the opisthosoma. However, the boundary of the prosoma is debatable in that some taxa have functionally incorporated somite VII and/or its appendages into the prosoma. Euchelicerata can be defined on having plate-like opisthosomal appendages, further modified within Arachnida. Total somite counts for Chelicerata range from a maximum of nineteen in groups like Scorpiones and the extinct Eurypterida down to seven in modern Pycnogonida. Mites may also show reduced somite counts, but reconstructing segmentation in these animals remains challenging. Several innovations relating to tagmosis or the appendages borne on particular somites are summarised here as putative apomorphies of individual higher taxa. We also present our observations within the concept of pseudotagma, whereby the true tagmata – the prosoma and opisthosoma – can be defined on a fundamental change in the limb series while pseudotagmata, such as the cephalosoma/proterosoma, are expressed as divisions in sclerites covering the body without an accompanying change in the appendages.     

Heme-binding storage proteins in the Chelicerata

Lipoglycoproteins in the Chelicerata that bind and store heme appear to represent a unique evolutionary strategy to both mitigate the toxicity of heme and utilize the molecule as a prosthetic group. Knowledge of heme-binding storage proteins in these organisms is in its infancy and much of what is known is from studies with vitellogenins (Vg) and more recently the main hemolymph storage protein in ixodid ticks characterized as a hemelipoglyco-carrier protein (CP). Data have also been reported from another arachnid, the black widow spider, Latrodectus mirabilis, and seem to suggest that the heme-binding capability of these large multimeric proteins is not a phenomenon found only in the Acari. CP appears to be most closely related to Vg in ticks in terms of primary structure but post-translational processing is different. Tick CP and L. mirabilis high-density lipoprotein 1 (HDL1) are similar in that they consist of two subunits of approximate molecular masses of 90 and 100 kDa, are found in the hemolymph as the dominant protein, and bind lipids, carbohydrates and cholesterol. CP binds heme which may also be the case for HDL1 since the protein was found to contain a brown pigment when analyzed by native polyacrylamide gel electrophoresis. Vgs in ticks are composed of multiple subunits and are the precursor of the yolk protein, vitellin. The phylogeny of these proteins, regulation of gene expression and putative functions of binding and storing heme throughout reproduction, blood-feeding and development are discussed. Comparisons with non-chelicerate arthropods are made in order to highlight the mechanisms and putative functions of heme-binding storage proteins and their possible critical function in the evolution of hematophagy.     

Hennig und der ursprung der tetrapoda

Hennig’s principle of analysis of characters is the best available method at present to analyse the relationship within one group or between groups. The analysis of characters has to be separated clearly from their phylogenetic and classificatory interpretation. New terms have been proposed to distinguish the status of classification of groups (synapogen, symplesiogen, paragen) from the character analysis (synapomorph etc.) and from its phylogenetic development (monophyletic, paraphyletic, polyphyletic). The origin of tetrapods is used as an example to show that every scheme of relationship depends on the use and evaluation of characters, the accepted homologies. A stabile classification is thus an illusion. No absolute criterion exists to recognize homologies.     

REVIEW Evolution and systematics of the Chelicerata

After approximately 40 years of discussion about the question of whether the Arthropoda are a monophyletic or a paraphyletic group or even a polyphyletic assemblage of unrelated taxa, most morphologists, palaeontologists and molecular taxonomists agree that the Arthropoda are a monophylum. The Euarthropoda are composed of the Arachnomorpha and Mandibulata. Myriapods are usually considered to be mandibulates; however, new molecular data as well as some morphological characters show similarities which the Myriapoda share with the Chelicerata, suggesting that there is no taxon Antennata or Atelocerata. Chelicerata are usually considered to be the sister group of Trilobita or, more correctly, Trilobita branch off from the chelicerate stem line. The first adaptive radiation of the Chelicerata took place in the Cambrian. All extant and some extinct orders were present during the Carboniferous. Two systems are compared. It is suggested that the Chelicerata contain the Pantopoda and Euchelicerata. The Euchelicerata are divided into Xiphosura and terrestrial Arachnida. Scorpiones are considered to be the sister group of all other arachnids, the Lipoctena and these are further divided into the Megoperculata (Uropygi, Amblypygi, and Araneae) and Apulmonata (all other groups). The Acari are tentatively considered to be a monophylum and the sister group of the Ricinulei. However, the Actinotrichida and Anactinotrichida diverged early and therefore have had a long history of independent evolution.     

Erweiterung der Aufgaben der Zwillingspathologie und Polymerie

Ohne Zusammenfassung     

Terminologie der Entwicklungsmechanik der Tiere und Pflanzen

Ohne Zusammenfassung     

Die funktionelle Struktur der Chordascheiden und der Wirbel bei Zyklostomen und Fischen

Ohne Zusammenfassung