Porcellio scaber | |
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P. scaber, head is left | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Arthropoda |
Class: | Malacostraca |
Order: | Isopoda |
Suborder: | Oniscidea |
Family: | Porcellionidae |
Genus: | Porcellio |
Species: | P. scaber |
Binomial name | |
Porcellio scaber | |
Synonyms | |
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Porcellio scaber (otherwise known as the common rough woodlouse or simply rough woodlouse), is a species of woodlouse native to Europe but with a cosmopolitan distribution. They are often found in large numbers in most regions, with many species (shrews, centipedes, toads, spiders and even some birds) preying on them.
One subspecies, Porcellio scaber lusitanus , is currently recognized. Two other subspecies were historically deemed valid but are no longer recognized. P. s. americanus, described in 1932, [2] was considered endemic in the Americas. P. s. japonicus was described in 1928 and believed to be endemic to Japan. [3] Both subspecies were synonymized with the nominate in 2020. [4]
Porcellio scaber is found across Central and Western Europe. [5] In the United Kingdom, it is one of the "big five" species of woodlice. It has also colonised North America, South Africa and other regions including the remote sub-Antarctic Marion island, largely through human activity. [6] It is also the most common species of woodlice found in Australia. [7]
Porcellio scaber has an oval body, can grow up to 20 millimetres (0.79 in) long, and is usually a grey colour, paler underneath, although, brown, blue, yellow, orange, or pinkish hues may also be observed. The dorsal (upper) surface of its segmented exoskeleton is covered in a series of small tubercles hence its common name.
At the head it has two pairs of antennae, with the inner pair being very small. Two compound eyes are located on the dorsal side of the head, while the mouthparts are on the ventral (lower) side.
There are 7 pairs of legs, corresponding to the 7 segments of the thorax. The short abdomen consists of 6 segments. [8] On the ventral side of the abdomen there are two whitish pseudo-lungs, connected with pores to the outside air. At the rear end there is a small telson flanked by a pair of appendages known as uropods. [8]
Porcellio scaber loses water by diffusion through its permeable exoskeleton which lacks a waxy cuticle. Because of this, to avoid desiccation, it often seeks out environments with humid air and plenty of ground moisture, preferably cold to minimize rate of water loss, and dark to avoid detection by predators. It lives in a wide variety of damp habitats but it is less dependent on high levels of humidity than Oniscus asellus . [9]
Porcellio scaber is a detritivore – it mainly feeds on decaying leaf litter but will consume any rotting plant matter. Living plants are of limited nutritional value for these woodlice which prefer to feed on the bacteria and fungi which cause decay. [10] P. scaber has very sensitive olfactory receptors that allow it detect the smell of microbial activity and to locate food. [11]
The females carry about 25 to 90 fertilized eggs until they hatch and are held in a fluid-filled sac at the ventral side of the abdomen for about 40–50 days. The young are reproductively mature after 3 months; the adult animals have a life expectancy of about two years. [8]
Porcellio scaber respond to certain stimuli with kinesis behaviour. [12] To attempt to find an environment where they lose less moisture and then stay there, P. scaber alter factors such as speed and rate of turning (orthokinesis and klinokinesis). When in a dry or hot environment, these woodlice have been observed increasing speed and turn more often in an attempt to leave the unfavorable environment. In a moist, dark, cool environment, they slow down dramatically and often stop altogether. To avoid desiccation, most woodlice (including P. scaber) exhibit thigmokinesis, slowing down or stopping when in contact with multiple surfaces (such as the corner of a box or a crack between two bricks). This behaviour leads to clumping of woodlice, reducing the exposed surface area through which water can be lost. Another manifestation of this is that a woodlouse in a Petri dish is unwilling to move into the center of the dish, preferring to stay near the edge.
Another reflex exhibited by P. scaber is turn alternation. During klinokinesis, turns alternate between left and right. This helps the woodlouse escape from a harmful environment or predator more efficiently as alternating turns average to form a straight line, unlike random turns which may well become a circle back to the predator. Several mechanisms for this have been proposed, such as short-term memory or following the outside wall, but the theory with most support is the bilateral asymmetrical leg movement (BALM) mechanism, which suggests that on the original turn, the legs on the outside of the turn become relatively more tired, so end up being overpowered by the legs on the inside of the turn, causing it to turn the opposite way from last time. [13]
Unlike the 'roller' species of woodlouse, such as Armadillidium spp., which are able to curl into a ball to defend themselves, P. scaber is a 'clinger' and adopts a posture of tonic immobility when faced with the threat of predation. A study of this thanatosis behaviour found that individuals of this species had unique personalities with shy woodlice staying still for longer and bold woodlice staying immobile for less time. [14]
Inspired by the behaviours of P. scaber, an algorithm for solving constrained optimization problems was proposed, called the Porcellio scaber algorithm (PSA). [15] [16]
Isopoda is an order of crustaceans. Members of this group are called isopods and include both aquatic species, and terrestrial species such as woodlice. All have rigid, segmented exoskeletons, two pairs of antennae, seven pairs of jointed limbs on the thorax, and five pairs of branching appendages on the abdomen that are used in respiration. Females brood their young in a pouch under their thorax called the marsupium.
Armadillidium vulgare, the common pill-bug, potato bug, common pill woodlouse, roly-poly, slater, doodle bug, or carpenter, is a widespread European species of woodlouse. It is the most extensively investigated terrestrial isopod species. It is native to Mediterranean Europe, but as an introduced species they have become naturalized in almost all suitable ecosystems. They are kept as pets by hobbyists for their wide range of possible color variations.
Porcellionidae is a terrestrial family of the order Isopoda.
Porcellio laevis is a species of woodlouse in the genus Porcellio. As the species epithet laevis as well as the vernacular name "swift woodlouse" suggests, the species is capable of quick bursts of speed when provoked.
Woodlice or roly-polies, are terrestrial isopods in the suborder Oniscidea. Their name is derived from being often found in old wood, and from louse, a parasitic insect, although woodlice are neither parasitic nor insects.
Trichoniscus pusillus, sometimes called the common pygmy woodlouse, is one of the five most common species of woodlice in the British Isles. It is acknowledged to be the most abundant terrestrial isopod in Britain. It is found commonly across Europe north of the Alps, and has been introduced to Madeira, the Azores and North America.
Ligidium hypnorum is a species of woodlouse found across Europe and western Asia. It is a fast-moving, active species that rarely grows longer than 9 mm (0.35 in). It is dark and shiny, and is similar in appearance to the common species Philoscia muscorum, and also the rarer Oritoniscus flavus. In Great Britain, it was first discovered at Copthorne Common, Surrey, in 1873, and most later records are also from South East England. It is considered a good indicator species for ancient woodland.
Hemilepistus reaumuri is a species of woodlouse or isopod that lives in and around the deserts of North Africa and the Middle East, "the driest habitat conquered by any species of crustacean, not including insects which are now known to be crustaceans pancrustacea". It reaches a length of 22 mm (0.87 in) and a width of up to 12 mm (0.47 in), and has seven pairs of legs which hold its body unusually high off the ground. The species was described in the Description de l'Égypte after the French Campaign in Egypt and Syria of 1798–1801, but was first formally named by Henri Milne-Edwards in 1840 as Porcellio reaumuri. It reached its current scientific name in 1930 after the former subgenus Hemilepistus was raised to the rank of genus.
Porcellio dilatatus is a species of woodlouse in the genus Porcellio belonging to the family Porcellionidae. This species is widespread in Europe, and has also been introduced to North America from Western Europe. They are 15 millimetres (0.59 in) long, are brown coloured and striped. They can be found feeding on alder leaves, but mostly feeds on organic food substrates, such as lettuce in the wild. It also feeds on inorganic metal salts.
Porcellio siculoccidentalis is a species of woodlouse in the genus Porcellio, which is endemic to western Sicily.
Armadillidium klugii is a lesser-known, rare Balkan, Dalmatia-based species of woodlouse, most distinguished by its colouration which resembles the red markings of the Mediterranean black widow Latrodectus tredecimguttatus. This is probably a kind of mimicry, to ward off predators that mistake the harmless animal for a venomous spider.
Armadillidium nasatum, the nosy pill woodlouse, is a large, Western European-based species of woodlouse that has been introduced to North America, along with Armadillidium vulgare also found in other parts of Europe.
Iridovirus armadillidium1, known formerly as Invertebrate iridescent virus 31 (IIV-31) and informally as isopod iridovirus, is a species of invertebrate iridescent virus in the genus Iridovirus. Oniscidea serve as hosts. Infection is associated with decreased responsiveness in the host, increased mortality and the emergence of an iridescent blue or bluish-purple colour due to the reflection of light off a paracrystalline arrangement of virions within the tissues.
Armadillidium maniatum is a European species of woodlouse endemic to Greece.
Armadillidium teramense is a European species of woodlouse endemic to Italy. It belongs to the "Orthotrigoniae" section of the genus and is currently known only from the type series.
Porcellio hoffmannseggii, commonly called the titan isopod, is a species of woodlouse of the genus Porcellio described in 1833. This very large species is native to the southern Iberian Peninsula, Morocco and the Balearic Islands.
Porcellio scaber lusitanus is a subspecies of Porcellio scaber endemic to Spain and Portugal. Described in 1907 as Porcellio lusitanus the species was later lowered to a subspecies level despite being referred to as a form. It is highly likely that Porcellio scaber lusitanus are normal P. scaber with Allometric Growth.
Armadillidium maculatum, also known as the zebra isopod or zebra pillbug is an Armadillidium species of woodlouse, named for its black and white patterns. It is native to southern France. It is quite popular as pets or vivarium cleaners, due to their ability to break down various waste.
Paraplatyarthrus australiensis is a species of woodlouse found in Western Australia. It was originally described in genus Trichorhina.