Cuthona nana
<p><em>Cuthona nana</em> (Alder & Hancock, 1842)</p>
Cuthona nana, L.8mm. Cerata extend forward of rhinophores in adults. Dark cerata reported to result from feeding on female, rather than male, Hydractinia. LWS (on rock; not on Hermit crab). Orkney, Scotland. August 1976. det. T.E.Thompson.
Species
Photographer / copyright holder
I.F. Smith
Length 8mm. Note that cerata extend in front of rhinophores.
Cuthona nana
Distribution and status
Brittany to Spitzbergen (GBIF map). All round Britain and Ireland where H. echinata occurs (UK distribution map).
The map provided here shows the distribution of the species based on Conchological Society data.
Ecology and behaviour
Low water spring tide to 30m. Usually on Hydractinia echinata on shells of Hermit crabs [4] on muddy sand in full salinity waters sheltered from waves. Sometimes on H. echinata growing on hard substrate where very strong currents or wave surge. Simultaneous hermaphrodite. Convoluted spiral of spawn laid on H. echinata. Veliger larvae drift as plankton for over two weeks before settling on the sea floor and transforming into the adult form. Breeds most months, with maximum in spring. Several generations each year.
Similar species
- Wide area of powdery surface pigment covers distal part of cerata; more extensive than on C. nana.
- Translucent smooth rhinophores tinted orange-brown.
- Not found on Hydractina on Hermit crabs.
Key identification features
- Smooth translucent white rhinophores, often with white surface marks.
- Cerata numerous, extend forwards of rhinophores in specimens over 8mm long [3].
- Powdery white dots on cerata concentrate into band distally [2].
- White surface pigment often on oral tentacles. [1].
- On Hydractina echinata, usually on shell of Hermit crab, but sometimes on hard substrate where strong current, or wave surge (EML).
References and links
Alder, J. & Hancock, A. 1845-1855. A monograph of the British nudibranchiate mollusca. London, Ray Society.
Thompson, T.E. & Brown, G.H. 1984. Biology of opisthobranch molluscs 2. London, Ray Society.
Irish distribution maps & prey organisms:
Picton, B.E. & Morrow, C.C., 2010. Encyclopedia of Marine Life of Britain and Ireland (EML).
Taxon version key
[NBNSYS0000174810]
Sort order
5990
Taxonomic group
Marine slug
Body (excluding appendages)