Argiope (genus)

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Argiope
Argiope anasuja in a wheel net with four stabilizations

Argiope anasuja in a wheel net with four stabilizations

Systematics
Class : Arachnids (arachnida)
Order : Spiders (Araneae)
Subordination : Real spiders (Araneomorphae)
Partial order : Entelegynae
Family : Real orb web spiders (Araneidae)
Genre : Argiope
Scientific name
Argiope
Audouin , 1826

Argiope is a genus from the family of the true orb web spiders (Araneidae) with almost worldwide distribution and comprises 81 species . (As of August 2016)

distribution

Species of the genus Argiope are distributed almost worldwide, with most of the species living in the tropics . The diversity center for the genus is the Indomalayan region of Southeast Asia and New Guinea , with 44 species. 15 species are known from mainland Australia . 11 species live in the African tropics ( Ethiopian region) and 7 in America. The fauna of the Palearctic comprises 13 species, 9 of which are restricted to the East Asian subtropics. Few species are widespread, Argiope bruennichi from Europe to Japan , Argiope lobata from Europe to Java. Argiope trifasciata occurs in North and South America , Hawaii , Australia, the Mediterranean region , large parts of Asia and Africa .

There are three common species in Europe:

features

Argiope differs from other genera of the real orb web spiders in the shape and arrangement of the eyes. The eight eyes of the real orb web spiders are arranged in two rows of four each. In Argiope , the rear (posterior) row of eyes is curved forward when viewed from above. The back eyes also differ structurally: the tapetum is reduced to a band, the inner rhabdome of the eyes have no tapetum. Both pairs of side eyes sit on a protrusion, the front side eyes on the front side, so that they cannot be seen when viewed precisely from above. The prosoma is relatively wide, often almost circular, the front part bearing the eyes is relatively small and narrow. His carapace usually has two comma-shaped depressions. In almost all species it is covered by fine, silvery or white, adjacent hairs. Of the relatively long pairs of legs, the first and second are almost the same length (the first a little longer), the fourth slightly, and the third significantly shorter than these. The abdomen (opisthosoma) is sometimes cylindrical, it is often unusually shaped, it can be flattened or pentagonal, in some species it has additional lobes on the sides. It is almost always brightly colored, often silvery white or golden yellow on top with black stripes, on the underside often black with two white longitudinal bands. Some species can arbitrarily and spontaneously change color as they flee the net from predators.

The epigyne of females usually has a pair of depressions with the openings at their base, which are separated in the middle by a septum, this is often widened plate-like towards the rear (a septum is missing e.g. in the wasp spider). A scapus, like most real orb web spiders, is missing. The male globe is complex. It has a long embolus with a large conductor and a small, median apophysis.

The very similar genera Gea and Neogea , which together with Argiope form the subfamily Argiopinae, differ from it in the arrangement of the eyes: In Argiope , the posterior median eyes are closer to each other than to the posterior lateral eyes. In the other genera, they are equally distant. However, these two genera only occur in Australia and the Pacific region (a Gea species also in America , possibly introduced here).

In all species, the males are smaller and often much smaller than the females. Most of the time, the color is different, so it is not easy to assign both sexes to a species.

Way of life and network construction

All species build bicycle nets , mostly they sit in the middle with the head pointing down. They are diurnal. Females lay their eggs in spun egg sacs in the vegetation near their webs, which sometimes have a species-specific shape.

Many Argiope species build nets which, in addition to the normal structure with a catch spiral, also have strikingly white stripes called " stabiliment ". The number and arrangement of the Stabilimente is different between the species, but highly variable, some species build nets with or without Stabiliment, depending on the circumstances, or their shape changes between juveniles and adults. Many species build two strips in a continuous band, others four of them, which then form an x-shaped structure. Stabiliments usually consist of wide, zigzag-shaped silk ribbons, with or without a plate-shaped widening in the hub of the net. There has been a scientific controversy about the function of the stabiliments for decades. The most important hypotheses about their function are: a) mechanical web reinforcements, b) structures that dissolve the body contour of the spider in the center of the web and thus protect it against optically hunting predators , c) sun sails that protect the animal against overheating, d) auxiliary constructions when catching prey which can attract flower-visiting insects especially through UV reflection. e) Optical guidance devices that make the cycle network more visible to birds and thus prevent damage caused by flying in. However, some arachnologists also deny any previously proposed function. Although stabiliments are particularly typical of Argiope , they are also found in other web-building spiders, such as the Uloboridae and Tetragnathidae families .

Sexual cannibalism

Argiope species are known for sexual cannibalism . The much smaller males are very often treated and eaten as prey by the female during or after copulation. Although it has been suggested that this could potentially be evolutionarily beneficial to the males because the better fed female could produce more offspring, it is generally viewed as disadvantageous to the males. The size difference itself was also interpreted as an advantage resulting from sexual selection . Males try to avoid attacks by the female by carefully approaching and fleeing in good time. In the species Argiope aurantia , more than 80 percent of the males were attacked by the female during mating. Attacks were particularly successful when the male had already inserted his eyeball into the female epigyne. Almost all of the males who survived the first mating attempted a second immediately afterwards. In the species studied so far, the males never seem to survive a second copulation. If they are not eaten, they will die soon. The embolus (part of the bulb) of the male breaks off regularly at a pre-formed fracture point and gets stuck in the epigyne of the female; it may make mating more difficult for other males who come later. In some cases it was these emboli that made it possible to assign males and females of certain species to one another.

Systematics

Argiope bruennichi , female

Taxonomy

The generic name was originally written Argyope by Victor Audouin, the original spelling was later suppressed by a resolution of the ICZN . Type species of the genus is Argiope lobata . The division of the genus into the genera Austrargiope , Chaetargiope , Coganargiope , and Heterargiope by the Japanese arachnologist Kyukichi Kishida has not caught on. Another synonym is Brachygea Caporiacco , 1947 .

Phylogeny

Together with the genera Gea and Neogea , Argiope forms the subfamily Argiopinae (this was much broader defined by earlier taxonomists, especially Eugène Simon ). After an analysis of morphological characteristics, the subfamily is monophyletic , its sister group could then be the subfamily Cyrtophorinae. A phylogenomic analysis of the relationships of the Argiopinae based on the comparison of homologous DNA sequences essentially confirmed earlier results, but the genus Argiope turned out to be paraphyletic compared to Gea and Neogea (this had already been assumed earlier in principle by Herbert Levi, who, however, had a splitting of the the distinctive genus Argiope ). The analysis confirmed neither an evolutionary trend in terms of height within the genus, nor one related to the size dimorphism between males and females.

species

The World Spider Catalog currently lists 81 species for the genus Argiope . (As of August 2016)

Individual evidence

  1. ↑ a b c Natural History Museum of the Burgergemeinde Bern: World Spider Catalog Version 17.5 - Argiope . Retrieved August 2, 2016.
  2. ↑ AV Tiunov & SL Esyunin (2015): Orb-weaver spiders of the genus Argiope (Aranei, Araneidae) from Russia and Central Asia. Entomological Review 95 (1): 99-107.
  3. ↑ a b Herbert W. Levi (2004): Comments and new records for the American genera Gea and Argiope with the description of a new species (Araneae, Araneidae). Bulletin of the Museum of Comparative Zoology 158 (2): 47-66.
  4. ↑ P. Di Pompeo, A. Kulzcyki, CM Legittimo, E. Simeon (2011): New records for Europe: Argiope trifasciata (Forsskal, 1775) from Italy and Malta (Araneae, Araneidae). Bulletin of the British Arachnological Society 15 (6): 205-208.
  5. ↑ Argiope at Fauna Europaea, version 2.6.2, updated August 29, 2013
  6. ↑ a b c Herbert W. Levi (1983): The orb weaver genera Argiope, Gea, and Neogea from the Western Pacific region (Araneae, Araeneidae, Argiopinae). Bulletin of the Museum of Comparative Zoology 150 (5): 247-338.
  7. ↑ ME Herberstein, CL Craig, JA Coddington, MA Elgar (2000): The functional significance of silk decorations of orb-web spiders: a critical review of the empirical evidence. Biological Revues 75: 649-669.
  8. ↑ MJ Bruce (2006): Silk decorations: controversy and consensus. Journal of Zoology 269: 89-97.
  9. ↑ Matthias W. Foellmer & Daphne J. Fairbairn (2004): Males under attack: sexual cannibalism and Its Consequences for male morphology and behavior in at orb-weaving spider. Evolutionary Ecology Research 6: 163-181.
  10. ↑ Peter Jäger (2012): A review on the spider genus Argiope Audouin 1826 with special emphasis on broken emboli in female epigynes (Araneae: Araneidae: Argiopinae). Contributions to Araneology 7: 272-331.
  11. ↑ Nikolaj Scharff & Jonathan A. Coddington (1997): A phylogenetic analysis of the orb-weaving spider family Araneidae (Arachnida, Araneae). Zoological Joumal of the Linnean Society 120: 355-434.
  12. ↑ Ren-Chung Cheng & Matjaž Kuntner (2014): Phylogeny suggests nondirectional and isometric evolution of sexual size dimorphism in argiopine spiders. Evolution 68 (10): 2861-2872. doi: 10.1111 / evo.12504

Web links

Commons : Argiope  - collection of images, videos and audio files

Argiope in the World Spider Catalog