Native
Nerocila orbignyi is an external parasite of fish which attaches itself to its host with its recurved dactyls. It can be distinguished from Anilocra sp. by its prominent coxal plates, the posterolateral angles of pereonites 2-6 being extended, and by its head not narrowing at the front to form a projection between the antennae.
Nerocila orbignyi has been found off the south coast of England as an external parasite on various fish, including Thick-lipped Grey Mullet, Mackerel and Herring. Unlike Anilocra sp., it typically attaches towards the rear of the fish.
Horton, T. & Baillie, C. 2019. Cymothoid isopods in UK Waters. PMNHS Bulletin 11, 44-50.
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.
World Register of Marine Species (WoRMS): https://www.marinespecies.org/aphia.php?p=taxdetails&id=118911
Ocean Biodiversity Information System (OBIS) distribution map: https://mapper.obis.org/?taxonid=118911
