Trichoniscus pusillus | |
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Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Arthropoda |
Class: | Malacostraca |
Superorder: | Peracarida |
Order: | Isopoda |
Suborder: | Oniscidea |
Family: | Trichoniscidae |
Genus: | Trichoniscus |
Species: | T. pusillus |
Binomial name | |
Trichoniscus pusillus | |
Synonyms [2] | |
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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. [3] It is found commonly across Europe north of the Alps, and has been introduced to Madeira, the Azores and North America. [4]
T. pusillus may be distinguished from other British woodlice chiefly by its small size, which reaches no more than 5 millimetres (0.2 in). [5] Its body is elongate and quite rounded in cross section, and typically purplish. [6] It may be separated from related species in North America by its eyes of three ocelli each, rather than the single ocellus in the eyes of its relative Hyloniscus riparius . [7]
There are two distinct reproductive strategies within the species Trichoniscus pusillus. Many populations are, like most metazoans, bisexual and reproduce sexually; in other cases, females reproduce parthenogenetically, creating clones of themselves. [8] The sexually reproducing form is diploid while the parthenogenetic form is triploid; [8] since parthenogenesis always produces females, males are always diploid and can only be produced by sexual reproduction.
The frequency of males in the population decreases from south to north (a latitudinal cline) and in increasingly open habitats, with no males observed in most of Scotland and Scandinavia, but more than 15% males in the Iberian and Apennine Peninsulas. [9]
The reproductive season lasts from March to September, and one to three breeding waves may be observed. Females are gravid for 4–5 weeks before releasing 4–18 mancae from the brood pouch. [10]
Like other woodlice, T. pusillus eats decaying plant matter of various kinds, although only alder litter is capable of sustaining a stable reproducing population. [10]
Predators of T. pusillus include the common shrew Sorex araneus , lycosid and dysderid spiders, centipedes such as Lithobius variegatus and perhaps carabid beetles. [11]
Trichoniscus pusillus is susceptible to infection by isopod iridescence virus, or Iridovirus (Iridoviridae). This is first apparent as a blue sheen on the unpigmented underside of the animals, but soon spreads to give the entire exoskeleton a bluish iridescence. [12]
Several former subspecies of T. pusillus are now treated as separate species. These include Trichoniscus alticola , Trichoniscus baschierii , Trichoniscus provisorius , Trichoniscus noriucs and Trichoniscus pygmaeus . [2]
Isopoda is an order of crustacean, which includes woodlice and their relatives. Members of this group are called Isopods and include both terrestrial and aquatic species. 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.
Porcellio scaber, 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 preying on them.
Oniscus asellus, the common woodlouse, is one of the largest and most common species of woodlouse in the British Isles and Western and Northern Europe, growing to lengths of 16 mm and widths of 6 mm.
Ligia oceanica, the sea slater, common sea slater, or sea roach, is a littoral zone woodlouse, living on rocky seashores of the European North Sea and Atlantic coastlines.
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.
A woodlouse 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.
Androniscus dentiger, the rosy woodlouse or pink woodlouse is a species of woodlouse found from the British Isles to North Africa.
Ligidium hypnorum is a species of woodlouse found across Europe and western Asia. It is a fast-moving, active species whichthat 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.
Armadillidium pictum is a species of woodlouse which occurs over most of Europe, except the Mediterranean Basin and Southeast Europe. In the British Isles, it is only known from a few sites, making it by some accounts, "Britain's rarest woodlouse". Since these sites are all remote from human habitation, in Cumbria and Powys, the species is thought to be native rather than introduced.
Hemilepistus reaumuri is a species of woodlouse that lives in and around the deserts of North Africa and the Middle East, "the driest habitat conquered by any species of crustacean". 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.
Reductoniscus costulatus is a species of woodlouse in the family Armadillidae. In the wild, R. costulatus has been found in Mauritius, the Seychelles and Hawaii, including the islands of Oʻahu and Kauaʻi and Hawaiʻi. It was discovered in the Palm House at the Royal Botanic Gardens, Kew in 1948, 1976 and 1988, and has been found in greenhouses across Europe.
Ligia is a genus of isopods, commonly known as rock lice or sea slaters. Most Ligia species live in tidal zone cliffs and rocky beaches, but there are several fully terrestrial species which occur in high-humidity environments.
Mesoniscus is a genus of woodlice, placed in its own family, Mesoniscidae, and section, Microcheta. It contains two species – Mesoniscus alpicolus and Mesoniscus graniger – that live in Central and Eastern Europe, mostly in and around caves.
Deto echinata, the horned isopod, is a species of air-breathing isopod, or woodlouse, in the family Detonidae. It inhabits seashores in southern Africa and on some oceanic islands.
Cylisticidae is a family of woodlice in the order Isopoda. There are at least 4 genera and more than 60 described species in Cylisticidae.
Helleria brevicornis, the sole species of the monotypic genus Helleria, is a terrestrial woodlouse endemic to the islands and coastal regions of the northern Tyrrhenian sea. H. brevicornis is of interest due to its endemism, unique ecology and basal position in the suborder Oniscidea.
Invertebrate iridescent virus 31 (IIV-31), also known 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 most strikingly, 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.
Hawaiioscia is a genus of woodlouse known from the Hawaii, Rapa Nui, and Costa Rica. The genus was originally described from Hawaii on the presence of four troglobitic species on separate islands. A species within this genus was then described from Rapa Nui which lacked troglobtic traits, but only persists in cave-dwelling relict populations. Surprisingly, another species was then described from along the Pacific Coast of Costa Rica.
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.