Phryxus longibranchiatus
Native
As with other species in this genus, the larger female (up to 8.0 mm) is asymetrical and pyriform in shape with prominent coxal plates and biramous pleopods. In the smaller male (2.0 mm), the pleon somites are fused. For further details, see Sars (1899, pp. 206-7 and Plate 86).
This species has been recorded in Shetland, the Isle of Man, and south Devon. It is the regular parasite (found in the branchial cavity) of the Squat Lobster Galathea squamifera, and may be detectable externally by a bulge in the carapace of the cephalothorax of the host.
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.
Sars, G. O. 1899. An Account of the Crustacea of Norway, Vol. II Isopoda. Bergen: Bergen Museum.
World Register of Marine Species (WoRMS): https://www.marinespecies.org/aphia.php?p=taxdetails&id=118226
Ocean Biodiversity Information System (OBIS) distribution map: https://mapper.obis.org/?taxonid=118226