Elektronenmikroskopische untersuchungen an den Guanin-Speicherzellen von Araneus diadematus clerck (Araneae,Araneidae)

Zusammenfassung Bei einigen Spinnen, vor allem aus der Familie der Araneidae, bilden funktionell umgewandelte Mitteldarmzellen unmittelbar unter der Hypodermic eine nahezu geschlossene Zellschicht, die mehr oder minder stark mit Guaninkristallen angefiillt sein kann.Die distalen Zellbereiche dieser von uns als Guanocyten bezeichneten Zellen verzahnen rich mit der Hypodermis selbst oder stehen mit dem schmalen hypodermalen Hämolymphsinus in Verbindung. Thre proximalen Enden sind lang ausgezogen und schieben sich zwischen nicht umgewandelte Resorptionszellen. Jede Guanocyte steht mit dem Mitteldarmlumen in direkter Verbindung.Auf Grund des Organellenbestandes sind die Guanocyten als spezialisierte Mitteldarmzellen auzusprechen, die während der reproduktiven Periode die übrigen exkretorisch tätigen Gewebe bzw. Organe unterstützen oder ergänzen, indem sie der Hämolymphe, der Hypodermis und den benachbarten Resorptionszellen pinocytotisch purinhaltige Abbauprodukte und andere Exkrete entnehmen. Dieselben werden unter Mitwirkung eines glatten endoplasmatischen Retikulums umgebaut und temporär intrazellulär als kompliziert aufgebaute Kristalle innerhalb von membranösen Kristallsäckehen gespeichert.Die Notwendigkeit intrazellulärer Exkretspeicherung auf Grund der Ernährungs-physiologie und Abwandlungen in der Funktionsmorphologie sowie fortschreitender Alterungserscheinungen wird diskutiert.

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Electromicroscopic studies of the guanine storage cells of Araneus diadematus Clerck (Araneae, Araneidae)

Summary Guanocytes are present in several spiders especially of the family Araneidae. The guanocytes form a compact cell-layer under the hypodermis. Their distal parts remain connected to the hypodermic hemolymph sinus, while the proximal ends establish contact with the midgut lumen in the shape of a long cellular process.The organelle equipment of the guanocytes shows that they are specialized midgut cells. They support or replace the other excretory tissues and organs especially during the reproduction period. By pinocytosis, the guanocytes remove catabolites of the purine and protein metabolism from the hemolymph, the adjacent resorption cells of the midgut, as well as from the overlying hypodermis cells. The stored catabolites are formed into complex crystals assisted by the smooth endoplasmic reticulum.The necessity of the temporary intracellular excretory storage on the basis of the physiology of nutrition, changes in the functional morphology, and general signs of old age are discussed.

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Die Untersuchungen werden dankenswerterweise von der Deutschen Forschnungsgemeinschaft durch Sach- und Personalmittel gefördert.

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Herrn Prof. Dr. H.-U. Koecke danke ich für seine Unterstützung und die Einräumung eines Arbeitsplatzes am Elektronenmikroskop.     

Previous experience and site tenacity in the orb spider Nephila (Araneae,Araneidae)

Summary The tenacity of the orb spider Nephila clavipes to a web site was studied in the laboratory. No differences were found between the giving-up-times and the site tenacity of spiders reared in the laboratory or those caught in the field, nor between spiders raised under a poor or a richt diet. The animals left sites at random and seemed to ignore experiences gained at previous sites.     

Organization of the spinnerets and spigots in the orb web spider,Argiope bruennichi (Araneae: Araneidae)

Although the basic taxonomic characteristics usually remain unchanged, some spinning apparatuses undergo consistent adaptive variations. As the presence of additional protuberances known as nubbins and tartipores have caused disagreements regarding some Araneidae spiders, more detailed definitions on the cuticular structures have recently been proposed. Reflecting this definition, microstructural organization of silk spinning apparatuses in the orb web spider Argiope bruennichi were reconsidered using field emission scanning electron microscopy. Among the seven kinds of functional spigots in females, it was revealed that two types (major ampullates and pyrifoms) are located on anterior spinnerets and another five types are distributed on median (minor ampullates, tubuliforms and aciniforms) or posterior (tubuliforms, flagelliforms, aggregates and aciniforms) spinnerets, respectively. In addition to functional spigots, cuticular remnants of the nubbins and the tartipores were found on the spinning fields, but the number of tartipores on each spinneret varied among individuals based on maturity. Nevertheless, three kinds of cuticular protuberances of ampullate silk glands were clearly visible at both the anterior and median spinnerets.     

Ultrastructure du canal des glandes agrégées et flagelliformes d'Araneus diadematus Clerck (Araneae,Araneidae)

Summary The excretory ducts of the silk glands which produce the viscid spiral of the webs ofAraneus diadematus show a complex structure. The duct of aggregate glands consists of three superposed types of cells. Several connective layers cover large and irregular nodule-forming cells which are rich in glycogen and mitochondria surrounded by invaginations of the plasma membranes. The internal cells, whose apical poles are lined by a cuticular intima, would be quite ordinary if not for the fact that they often carry large vacuoles which seem to empty themselves by exocytosis. Activity in the nodule cells is perceived from variations in the glycogen level and from the appearance of the mitochondria. Internal cells of the duct, when within the posterior spinneret, gradually acquire the characteristics of absorbing cells.The duct of flagelliform glands consists of two types of cells. The external cells, bounded by a simple basal lamina, are rich in mitochondria, glycogen, and invaginations of the plasma membranes; their activity is shown by variations in glycogen level and the extent of the extracellular spaces. The internal cells show numerous mitochondria either at the apical or basal poles, variable glycogen levels, long microvilli, and signs of apical absorption by pinocytosis; the sub-cuticular layer of the intima is particularly thick.We propose a functional interpretation of the aspects described above, and discuss it in terms of recent data on the chemical composition of silks. The excretory ducts are held to modify, by their activity, the secretory products of both types of glands. Solutes, especially phosphate ions, cross both cells and intima and would enter the glue of the aggregate glands which then undergoes partial dehydration in the posterior spinnerets. The product of the flagelliform glands seems to all appearance dehydrated during its passage in the duct and up to about the half-way through the posterior spinnerets. The liquid would flow through an extracellular path below the apical septate junctions of the internal cells. This study therefore favours attributing important role to the excretory ducts of silk glands in the final phase of the formation of silk fibres by spiders.     

Untersuchungen zur Taxonomie der Gattung Araniella (Araneae, Araneidae)

Morphological and ethological criteria were used in studying the taxonomic relations between different forms within the genus Araniella . Criteria for a diagnosis of all species and subspecies of the genus are given. A. opisthographa (Kulczyski, 1905), A. cucurbitina (Clerck, 1757), A. proxima (Kulczyski, 1885) and A. maderiana (Kulczyski, 1905) form one group of sibling species in the narrowest sense, A. alpica (L. Koch, 1869) and A. inconspicua (Simon, 1874) a second distinct one. A. displicata (Hentz, 1847) seems to occupy a relatively isolated position. A. cossoni (Simon, 1885) is regarded as a synonym for A. cucurbitina . It is impossible to make a statement about the status of A. silesiaca (Fickert, 1876) and A. croatica (Kulczyski, 1905) because of the lack of sufficient material. A. silesiaca is not a synonym for Araneus crispulus Tullgren, 1952, a species which does not belong to the genus Araniella .     

Oldest true orb-weaving spider (Araneae: Araneidae)

The aerial orb web woven by spiders of the family Araneidae typifies these organisms to laypersons and scientists alike. Here we describe the oldest fossil species of this family, which is preserved in amber from Alava, Spain and represents the first record of Araneidae from the Lower Cretaceous. The fossils provide direct evidence that all three major orb web weaving families: Araneidae, Tetragnathidae and Uloboridae had evolved by this time, confirming the antiquity of the use of this remarkable structure as a prey capture strategy by spiders. Given the complex and stereotyped movements that all orb weavers use to construct their webs, there is little question regarding their common origin, which must have occurred in the Jurassic or earlier. Thus, various forms of this formidable prey capture mechanism were already in place by the time of the explosive Cretaceous co-radiation of angiosperms and their flying insect pollinators. This permitted a similar co-radiation of spider predators with their flying insect prey, presumably without the need for a 'catch-up lag phase' for the spiders.     

The Spider Genera Singa and Hypsosinga (Araneae, Araneidae) in Israel

Israeli spiders of the orb-weaver genera Singa and Hypsosinga (Araneidae) have been revised. New and updated information on the little known Mediterranean spider fauna, pertaining to European species as well, is presented. Some of the species have never been adequately described or illustrated. All the species previously described from the Middle East and adjacent countries were re-examined. Aranea neta is newly placed in Singa and the following new synonyms are defined: Lithyphantes sepfemguffafus Simon, 1873, along with Araneus decorus (Simon, 1891) and Lithyphantes pollocki Denis, 1956 = Singa neta (O. P.-Cambridge, 1872); Singa afjinis O. P.-Cambridge, 1876 along with Singa attica Simon, 1884 = Hypsosinga albovittata (Westring, 1851). The presence of three species formerly reported from Israel, including one erroneously determined, has been confirmed, and the occurrence of another three species previously unknown from this country has been proved. All are newly described. Keys, detailed illustrations of diagnostic characters and records of -distribution are provided for each species.     

Untersuchungen zum Sexualverhalten von Cyrtophora cicatrosa (Stoliczka) (Araneae,Araneidae)

Courtship and copulation behaviour of the tropical spicier Cyrtophora cicatrosa were observed in the laboratory. They are described and compared with the behaviour of C. citricola. Emphasis is placed on the roles of pheromones and web tapping, and on the species' different ways of overcoming the problems resulting from extreme sexual dimorphism.     

Design features of the orb web of the spider, Araneus diadematus

Analysis of orb webs of the garden cross spider (Araneus diadematus)showed that these vertical webs have a significant up/down asymmetry.Experiments demonstrated that the spider runs down faster thanup, and thus confers a relatively higher foraging value to sectionsbelow the hub. Simulations suggested that the density of capturespiral spacing, prey size, and the density of prey should allaffect the capture efficiency of a web. Webs lose effectivecapture area because of overlap of the capture zone around eachthread; the smaller the prey, the finer the mesh can be withoutlosing effective area. Lower sectors of the web have a particularmesh size (height and length of capture spiral segments) throughout,whereas in the upper sectors the mesh size changes, wideningfrom the hub towards the periphery.     

Phylogeny of the orb-weaving spider family Araneidae (Araneae: Araneoidea)

We present a new phylogeny of the spider family Araneidae based on five genes (28S, 18S, COI, H3 and 16S) for 158 taxa, identified and mainly sequenced by us. This includes 25 outgroups and 133 araneid ingroups representing the subfamilies Zygiellinae Simon, 1929, Nephilinae Simon, 1894, and the typical araneids, here informally named the “ARA Clade”. The araneid genera analysed here include roughly 90% of all currently named araneid species. The ARA Clade is the primary focus of this analysis. In taxonomic terms, outgroups comprise 22 genera and 11 families, and the ingroup comprises three Zygiellinae and four Nephilinae genera, and 85 ARA Clade genera (ten new). Within the ARA Clade, we recognize ten informal groups that contain at least three genera each and are supported under Bayesian posterior probabilities (≥ 0.95): “Caerostrines” (Caerostris, Gnolus and Testudinaria), “Micrathenines” (Acacesia, Micrathena, Ocrepeira, Scoloderus and Verrucosa), “Eriophorines” (Acanthepeira, Alpaida, Eriophora, Parawixia and Wagneriana), “Backobourkiines” (Acroaspis, Backobourkia, Carepalxis, Novakiella, Parawixia, Plebs, Singa and three new genera), “Argiopines” (Arachnura, Acusilas, Argiope, Cyrtophora, Gea, Lariniaria and Mecynogea), “Cyrtarachnines” (Aranoethra, Cyrtarachne, Paraplectana, Pasilobus and Poecilopachys), “Mastophorines” (Celaenia, Exechocentrus and Mastophora,), “Nuctenines” (Larinia, Larinioides and Nuctenea), “Zealaraneines” (Colaranea, Cryptaranea, Paralarinia, Zealaranea and two new genera) and “Gasteracanthines” (Augusta, Acrosomoides, Austracantha, Gasteracantha, Isoxya, Macracantha, Madacantha, Parmatergus and Thelacantha). Few of these groups are currently corroborated by morphology, behaviour, natural history or biogeography. We also include the large genus Araneus, along with Aculepeira, Agalenatea, Anepsion, Araniella, Cercidia, Chorizopes, Cyclosa, Dolophones, Eriovixia, Eustala, Gibbaranea, Hingstepeira, Hypognatha, Kaira, Larinia, Mangora, Metazygia, Metepeira, Neoscona, Paraplectanoides, Perilla, Poltys, Pycnacantha, Spilasma and Telaprocera, but the placement of these genera was generally ambiguous, except for Paraplectanoides, which is strongly supported as sister to traditional Nephilinae. Araneus, Argiope, Eriophora and Larinia are polyphyletic, Araneus implying nine new taxa of genus rank, and Eriophora and Larinia two each. In Araneus and Eriophora, polyphyly was usually due to north temperate generic concepts being used as dumping grounds for species from southern hemisphere regions, e.g. South-East Asia, Australia or New Zealand. Although Araneidae is one of the better studied spider families, too little natural history and/or morphological data are available across these terminals to draw any strong evolutionary conclusions. However, the classical orb web is reconstructed as plesiomorphic for Araneidae, with a single loss in “cyrtarachnines”–“mastophorines”. Web decorations (collectively known as stabilimenta) evolved perhaps five times. Sexual dimorphism generally results from female body size increase with few exceptions; dimorphic taxa are not monophyletic and revert to monomorphism in a few cases.     

Size-related mating and mate guarding in the orb-web spiderNephila clavata (Araneae,Araneidae)

The orb-web spiderNephila clavata satisfies three conditions for assortative mating proposed by Ridley (The Explanation of Organic Diversity. The Comparative Method and Adaptations for Mating, Clarendon, Oxford, 1983); (1) a large male advantage in male-male competition, (2) a correlation between female size and fecundity, and (3) a long pairing duration. To test Ridley's hypothesis, size assortative mating and guarding were examined in the field. When data were pooled over time, assortative mating was found but this was due to temporal covariation of body sizes of males and receptive females. After controlling for the effect of time, size assortative guarding was not detected, although females guarded by males were larger than those not guarded in the early breeding season. Possible reasons for the absence of size assortative guarding were discussed.     

A phylogenetic analysis of the orb-weaving spider family Araneidae (Arachnida, Araneae)

We present the first cladistic analysis focused at the tribal and subfamily level of the orb-weaving spider family Araneidae. The data matrix of 82 characters scored for 57 arancid genera of 6 subfamilies and 19 tribes (and 13 genera from 8 outgroup families) resulted in 16 slightly different, most parsimonious trees. Successive weighting corroborated 62 of the 66 informative nodes on these cladograms; one is recommended as the 'working' araneid phylogcny. The sister group of Araneidae is all other Araneoidea. Araneidae comprises two major clades: the subfamily Araneinae, and the 'argiopoid' clade, which includes all other subfamilies and most tribes (((Gasteracanthinae, Caerostreae), (((Micratheninae, Xylcthreae), Eruyosaccus ), (Eurycorminae, Arciinae)), Cyrlarachninae), ((Argiopinae, Cyrtophorinae), Arachnureae)). Cyrtarachneae and Mastophoreae are united in a new subfamily, Cyr-tarachninae. The spiny orb-weavers alone (Gasteracanthinae and Micratheninae) are not monophyletic. The mimetid subfamily Arciinae and the 'tetragnathid' genus Zygiella are araneids, but .Nephila (and other tetragnathids) are not. On the preferred tree, web decorations (stabilimenta) evolved 9 times within 15 genera, and were lost once. The use of silk to subdue prey evolved once in cribellate and four times in ecribillate orb weavers. Sexual size dimorphism evolved once in nephilines, twice in araneids, and reverted to monomorphism five times. Evolution in other genitalic and somatic characters is also assessed; behavioral and spinneret features arc most consistent (male genitalia, leg and prosomal features least consistent) on the phylogeny.     

Selected aspects of spinning apparatus development in Araneus cavaticus (Araneae,Araneidae)

In the first half of this century, several workers observed small, seemingly glandular structures attached to the ampullate glands of spiders. Hence, they were termed accessory ampullate glands. In juvenile Araneus cavaticus, two pairs of these structures are present (starting at least with third instars), one pair attached to the major ampullate (MaA) glands and the other pair attached to the minor ampullate (MiA) glands. In adults, two pairs of accessory MaA glands and two pairs of accessory MiA glands are present. The two latter-formed pairs of accessory ampullate glands are clearly the remnants of those ampullate glands which atrophy shortly after adulthood is reached. Morphological similarities between these accessory ampullate glands and those present in juveniles provide an indication that the latter also have their origin in functional ampullate glands. A reduction in the number of ampullate glands following the last molt occurs in many spiders. The reason(s) for these reductions is unknown. In penultimate spiders close to ecdysis, we have observed that while the larger pairs of MaA and MiA glands (those that are retained in the adult) are undergoing molt-related changes which apparently render them nonfunctional, their smaller counterparts are seemingly unaffected and functional. This raises the possibility that the principal role of the smaller ampullate glands may be to assume functions during the pre-ecdysial period which are normally in the domain of the larger ampullate glands. If true, then their degeneration after the last molt would make economic sense. The presence of cylindrical spigots in juvenile females starting with fourth instars is documented.     

Memory of distances and directions moved as cues during temporary spiral construction in the spiderLeucauge mariana (Araneae: Araneidae)

The spider Leucauge marianaprobably uses the presence of temporary spiral (TSP) lines already in place to determine sites of attachment of currently produced loops of temporary spiral, but less rigidly than has been previously supposed for orb weavers. Memory of distances and directions traveled recently to and from TSP lines is implicated by the fact that adjustments to experimental and natural discontinuities in previous TSP lines occur gradually rather than being abrupt. Distances and directions traveled along both radii and previous TSP lines correlate with relative amounts of adjustment. Body size may also be used as a reference measure, but not in the simple, inflexible way suggested by R. W. G. Hingston (A Naturalist in Himalaya,Small, Maynard, Boston, 1920). Tensions on radii are not used as cues in any simple way, and may not be used at all, since experimental changes in tensions produced effects consistent with resulting changes in thread positions but inconsistent with tension differences.     

山西痣蛛属1新记录种(蜘蛛目:园蛛科)

报道了产自山西南部痣蛛属1新记录种,即八木氏痣蛛Araniella yaginumai Tanikawa,1995 .     

Optische Lokalisation der Beute bei der KreuzspinneAraneus diadematus Clerck (Araneae araneidae)

Zusammenfassung Es wird die Bedeutung von optischen Reizen in der Anfangsphase des Beutefangs bei Araneus diadematus Clerck nachgewiesen. Optische und vibratorische Reize tragen beide, nach der Reizsummenregel, zur Auslösung der Beutefangreaktion bei. Die Taxiskomponenten der optischen bzw. vibratorischen Reize schließen sich jedoch in ihrem Einfluß auf die Endrichtung der motorischen Reaktion von Araneus gegenseitig aus; sie wirken kompetitiv, und das Überwiegen der einen oder anderen Taxiskomponente hängt von den topographischen Eigenschaften der Reize ab.