Astacilla damnoniensis (Stebbing, 1874)
Astacilla species are distinctive marine isopods that are mostly sublittoral but can occasionally turn up in the intertidal zone. They have long antennae with extended 4th and 5th segments, an elongated middle pereon segment, short walking legs on pereon segments 5 to 7, and usually with adapted, setose legs on pereon segments 1 to 4 that are directed towards the mouth for feeding. The pereon segments are typically ornamented with tubercles and/or spines.
A. damnoniensis grows up to 10mm in length. It has three tubercles on its head, it has a medial tubercle on each pereon segment (especially prominent on segment 4), and the lateral borders of the pleotelson are serrated.
Distribution and Habitat
Astacilla species are filter feeders that typically cling to seaweed, echinoderms, coelenterates, etc.
Found sublittorally around Britain and Ireland, A. damnoniensis is occasionally recorded intertidally, especially in south-west England and south Wales.
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.