Campecopea hirsuta (Montagu, 1804)
This is a small Sphaeromatid isopod with marked sexual dimorphism. Distinguished from other species by having a single uropod ramus, the pleotelson of females is rounded whilst males have a long projection from pereonite 6 which extends to the distal border of the pleotelson. Males grow up to 4.0mm, females up to 3.5mm.
Distribution and Habitat
Campecopea hirsuta is most commonly found in the intertidal lichen Lichina pygmaea ((Lightf.) C. Agardh, 1817), amongst barnacles and in rock crevices on exposed shores between MTL and HWN. It is most easily found by scraping some Lichina pygmaea into a tray of water, where the species may then be seen swimming freely.
The species occurs in south-west England, from Dorset to north Devon, and in south-west Wales from Gower northwards to Anglesey (Harvey 1968). It also occurs along the southern coast of Ireland, from at least Rosslare in the south-east to Dunmanus Bay in the south-west (McGrath 1982). Both Harvey (1968) and McGrath (1982) noted that the species appears to be absent from Galway Bay, but whether it has a somewhat wider distribution than indicated in McGrath (1982) remains unknown.
It might seem that a report of this species (referred to as Campecopea cranchii) from Banffshire in north-east Scotland in Edward (1876) can hardly be accepted at face value given the northerly location and the inclusion of other southerly species in his list (e.g. (Halo)Philoscia couchii), but the find of a single female C. hirsuta on the Berwickshire coast in 2021 suggests that odd individuals of this species can turn up well outside of its normal range.
Edward, T. 1876. Selections from the fauna of Banffshire. In Smiles S., Life of a Scotch Naturalist, 389-438.
Harvey, C. 1968. Distribution and seasonal population changes of Campecopea hirsuta [Isopoda: Flabellifera]. Journal of the Marine Biological Association UK 48, 761-7.
McGrath, D. 1982. Some Distributional Records for the Marine Isopod, Campecopea hirsuta (Montagu) in Irish Waters. The Irish Naturalists' Journal 20, No. 11, 500-2.
Naylor, E. & A. Brandt. 2015. Intertidal Marine Isopods. Synopses of the British Fauna (New Series), No. 3. Field Studies Council, for The Linnean Society of London.