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   Porcellio scaber (crustacean)
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         Interim profile, incomplete information
    Taxonomic name: Porcellio scaber Latreille, 1804
    Synonyms: Oniscus granulatus Lamark 1818, Porcellio asper Koch 1847, Porcellio brandlii Milne-Edwardes 1840, Porcellio dubius Koch 1840, Porcellio graniger Biidde-Lund 1885, Porcellio graniger Miers 1876, Porcellio montezumaex Saussure 1857, Porcellio nigra Say 1818, Porcellio paulensis Heller 1865, Porcellio seaber Bate and Westwood 1868
    Common names: woodlouse
    Organism type: crustacean
    The terrestrial crustacean Porcellio scaber was first recorded on the sub-Antarctic Marion Island during a survey in April 2001. Searches conducted between September 2001 and April 2002 yielded as many as 391 specimens including gravid females. There are concerns that P. scaber may have an impact on native invertebrates in its introduced range. For example, Gough Island's only indigenous terrestrial isopod Styloniscus australis is rare in lowland habitats where the introduced terrestrial isopod P. scaber is abundant; however it is abundant on upland sites where P. scaber is rare. P. scaber may also compete with primary native detritivores on Marion Island such as Pringleophaga marioni and earthworms.
    Description
    The body of Porcellio scaber is densely covered with tubercles. Its colour is usually a very dark grey, but can also be quite red or variegated with yellow. Albino specimens have been recorded. The two joints of the flagellum are of the same length and together equal that of the last joint of the peduncle. Air-tubes are present on the outer plates of the first two abdominal appendages (Webb & Sillem 1906).
    Occurs in:
    planted forests, urban areas
    Habitat description
    Porcellio scaber not only inhabits litter stratum in forests, but also inhabits middens, gardens, and cellars in human habitations, preferring moist microclimates (Wang & Schreiber 1999).

    Several studies have investigated the low-temperature tolerance of P. scaber. In the Palearctic, this species has a lower lethal temperature of approximately minus 4.6 degC (Tanaka and Udagawa 1993, in Slabber & Chown 2002) and can survive for at least 1 week at minus 2 degC, so long as individuals have access to food and have been previously exposed to relatively low, but not subzero, temperatures (Lavy et al. 1997, in Slabber & Chown 2002).

    General impacts
    Porcellio scaber has an island wide range on Gough Island and introduced invertebrates form a large proportion of the invertebrate community. Introduced detritivores on Gough like P. scaber, lumbricid worms, and the millipede Cylindroiulus latestriatus can have long term effects on nutrient cycles of its peaty soils, that lack such species and have formed in the absence of rapid organic breakdown. Long term effects can include changes in flora and faunal communities (Jones et al. 2003).

    There are concerns that P. scaber may have an impact on native invertebrates. For example, Gough Island's only indigenous terrestrial isopod Styloniscus australis is rare in lowland habitats where the introduced terrestrial isopod P. scaber is abundant; however it is abundant on upland sites where P. scaber is rare. P. scaber may also compete with primary native detritivores on Marion Island such as Pringleophaga marioni and earthworms (Jones et al. 2003).

    Geographical range
    The isopod Porcellio scaber is of European origin although it is now cosmopolitan (Frenot et al. 2005). P. scaber is an abundant inhabitant of litter stratum in western and central European forests. Descended from subspecies Porcellio scaber lusitanus Verhoeff, 1907, which is endemic in the Atlantic regions of the Iberian Peninsula, P. scaber has spread through distribution of forest litter and through human habitation eastwards to Poland and the Baltic states. It has also spread to sites in Greenland and North America (Wang & Schreiber 1999). P. scaber has an island wide range on Gough Island. It was first recorded on the sub-Antarctic Marion Island during a survey in April 2001. Searches conducted between September 2001 and April 2002 yielded as many as 391 specimens including gravid females. It is likely to have been introduced with building supplies from Cape Town or from Gough Island (Slabber & Chown 2002).
    Introduction pathways to new locations
    Agriculture: Porcellio scaber may be moved to new locations through human-aided dispersal, for example, through the movement of ballast, rubble, agricultural products, compost and plants (Wang & Schreiber 1999, in Slabber & Chown 2002).
    Horticulture: Porcellio scaber may be moved to new locations through human-aided dispersal, for example, through the movement of ballast, rubble, agricultural products, compost and plants (Wang & Schreiber 1999, in Slabber & Chown 2002).
    Transportation of habitat material: Porcellio scaber may be moved to new locations through human-aided dispersal, for example, through the movement of ballast, rubble, agricultural products, compost and plants (Wang & Schreiber 1999, in Slabber & Chown 2002).
    Management information
    On Marion Island the most appropriate conservation strategy would be complete eradication of Porcellio scaber. This recommendation has been made to the Prince Edward Islands Management Committee, which oversees conservation at the islands (Marion and Prince Edward islands). Eradication attempts are now underway (Slabber & Chown 2002).
    Nutrition
    Porcellio scaber feeds on detritus (Slabber & Chown 2002). On Marion Island P. scaber feeds on detritus including plant and animal remains, soil algae and fungi, as is the case with most isopods (Barnes 1980, Warburg 1993, Lavy et al. 2001, in Slabber & Chown 2002).
    Reproduction
    On Marion Island Porcellio scaber appears to be reproductively most active over the summer months from October until March (Slabber & Chown 2002). Day-length variation and low temperatures might be responsible for inducing seasonal reproduction (Slabber & Chown 2002).
    Lifecycle stages
    Juveniles are carried ventrally by the females characteristic of this species (Carefoot 1993, in Slabber & Chown 2002).
    Principal sources: Slabber, S. & S. L. Chown, 2002. The first record of a terrestrial crustacean, Porcellio scaber (Isopoda, Porcellionidae), from sub-Antarctic Marion Island. Polar Biol (2002) 25: 855–858
    Compiled by: IUCN SSC Invasive Species Specialist Group (ISSG) with support from the EU-funded South Atlantic Invasive Species project, coordinated by the Royal Society for the Protection of Birds (RSPB)
    Last Modified: Tuesday, 28 April 2009


ISSG Landcare Research NBII IUCN University of Auckland