Similar in appearance to Janira maculosa, this species is somewhat more elongate and has relatively shorter antennae and uropods. It also has a smoother outline, and the male preoperculum is distinctive. Males grow to 6 mm, females to 4 mm.
J. breviremis has similar habitat preferences to Janira maculosa, being found in and among sponges, bryozoans, Laminaria holdfasts, etc. It is mostly a sublittoral species, but occasionally turns up intertidally (e.g. it has been recorded amongst Halidrys seaweed at Cullercoats in north-east England; see Foster-Smith 2000).
Foster-Smith, J. 2000. The Marine Fauna and Flora of the Cullercoats District: Marine Species Records for the North East Coast of England (Volume 1). Sunderland: Penshaw Press.
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.
http://www.marinespecies.org/aphia.php?p=taxdetails&id=118714