Jaera (Jaera) praehirsuta Forsman, 1949
Jaera are small, ubiquitous intertidal marine isopods which can be identified to species by the examination of male reproductive structures (specifically the preoperculum) and pereopods. Preopercula can be examined using a binocular dissecting microscope, but examination of pereopods is best done using a compound microscope at low power.
Jaera praehirsuta is one of the 'albifrons' group of species (along with Jaera albifrons, Jaera forsmani and Jaera ischiosetosa), all of which have a T-shaped male preoperculum. It can be distinguished from the other species by the presence of a dense covering of setae on the propodus, carpus and merus of the male 6th and 7th pereopods. The carpal spine on pereopod 6 is poorly developed. Males up to 3.0mm, females up to 4.5mm. See further the Identifying Jaera page.
Distribution and Habitat
Not well reported but certainly more common and widespread than indicated in the NBN map (it has been recorded in several locations in south-east Scotland, for example). Mostly among fucoid algae up to HWN.
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.