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A woodlouse (plural woodlice) is any crustacean belonging to the suborder Oniscidea within the order Isopoda. They get their name from often being found in old wood, and from louse, a parasitic insect, although woodlice are neither parasitic nor insects. Woodlice evolved from marine isopods which are presumed to have colonised land in the Carboniferous, though the oldest known fossils are from the Cretaceous period. They have many common names and although often referred to as terrestrial isopods, some species live semiterrestrially or have recolonised aquatic environments. Woodlice in the families Armadillidae, Armadillidiidae, Eubelidae, Tylidae and some other genera can roll up into a roughly spherical shape (conglobate) as a defensive mechanism; others have partial rolling ability, but most cannot conglobate at all. Woodlice have a basic morphology of a segmented, dorso-ventrally flattened body with seven pairs of jointed legs, specialised appendages for respiration and like other peracarids, females carry fertilised eggs in their marsupium, through which they provide developing embryos with water, oxygen and nutrients. The immature young hatch as mancae and receive further maternal care in some species. Juveniles then go through a series of moults before reaching maturity.
While the broader phylogeny of the Oniscideans has not been settled, eleven infraorders/sections are agreed on with 3,937 species validated in scientific literature in 2004 and 3,710 species in 2014 out of an estimated total of 5,000–7,000 species extant worldwide. Key adaptations to terrestrial life have led to a highly diverse set of animals; from the marine littoral zone and subterranean lakes to arid deserts and desert slopes 4,725 m (15,500 ft) above sea-level, woodlice have established themselves in most terrestrial biomes and represent the full range of transitional forms and behaviours for living on land. Woodlice are widely studied in the contexts of evolutionary biology, behavioural ecology and nutrient cycling. They are popular as terrarium pets because of their varied colour and texture forms, conglobating ability and ease of care. Recent research has shown that the grouping as traditionally defined may not be monophyletic, with some taxa like Ligia and possibly Tylidae more closely related to other marine isopod groups, though the majority of woodlice probably form a monophyletic clade.
Woodlice, also known as pillbugs or sowbugs, are a type of crustacean that can be found in terrestrial environments. They have a shell-like exoskeleton, which they shed as they grow. Female woodlice keep fertilized eggs in a marsupium on their bodies and can reproduce both sexually and asexually. Woodlice are usually found in damp, dark places and feed on dead plant matter. They can also invade homes in search of moisture. Woodlice are considered beneficial in gardens but can also damage cultivated plants. They are sometimes kept as pets or used in bioactive terrariums. The classification of woodlice is divided into five main lineages within the suborder Oniscidea. The oldest fossils of woodlice date back to the mid-Cretaceous period, around 100 million years ago.
Die Landasseln (Oniscidea) sind eine an Land lebende Unterordnung der Asseln (Isopoda). Sie sind die einzigen dauerhaft an Land lebenden Krebstiere, und im Gegensatz zu Landeinsiedlerkrebsen und anderen temporär an Land lebenden Krebsgruppen können sie sich auch außerhalb des Wassers fortpflanzen. Weltweit gibt es mehr als 3700 bekannte Landasselarten, die sich auf mehrere Familien verteilen. In Deutschland sind rund 50 Arten heimisch.
Die Zusammenfassung besagt, dass Landasseln zur Unterordnung der Asseln gehören und verschiedene anatomische Merkmale aufweisen. Sie haben reduzierte Antennen und fehlende Palpen an den Mandibeln. Die Landasseln sind zwischen zwei und 20 Millimeter lang, dorsoventral abgeflacht und langoval. Sie haben einen Kopf, der mit dem ersten Brustabschnitt verschmolzen ist, und tragen verschiedene Mundwerkzeuge sowie zwei Antennenpaare. Die Landasseln haben physiologische Anpassungen an das Landleben entwickelt, wie verzweigte Einstülpungen an den Exopoditen der Pleopoden, die Luft aufnehmen und Sauerstoff aufnehmen können. Die meisten Landasseln bevorzugen feuchte Lebensräume und sind nachtaktiv, während sich einige Arten an trockenere Lebensräume angepasst haben. Landasseln sind weltweit in allen terrestrischen Lebensräumen außer den polaren Gebieten verbreitet. Die größte Artenvielfalt findet man in den Tropen und Subtropen. Die Systematik der Landasseln ist gut abgesichert, jedoch schließt sie die Gattung Ligia, die eng mit marinen Asselarten verwandt ist, aus.