Synonyms Flabellina lineata (Lovén, 1846) Coryphella lineata (Lovén,1846)
Flabellina/Coryphella lineata was split into several species (Korshunova et al 2017), two of which live in British waters; Fjordia lineata sensu stricto and Fjordia chriskaugi. The specimens shown in this account are F. lineata s.s. as the opaque white pigment line on each ceras is not fragmentary and it broadens into a cap at the tip. On F. chriskaugi the lines are less complete and do not form caps, but make sure not to confuse the translucent white cnidosac within the tip with opaque white surface pigment.
Body (excluding appendages)
Usually up to 30 mm long, occasionally 50mm. Translucent white with, usually near-continuous, opaque white dorsal line from in front of rhinophores to posterior group of cerata [image1], and a similar line on each side from the anterior group of cerata to the tip of the tail , the two lateral lines uniting on the tail to make a doubly thick line. Viscera visible in anterior half of translucent body, and white ovotestis lobules visible in the posterior of mature specimens . Posterior half of juveniles, under circa 9 mm, lack ovotestis so substrate visible through body .
Cerata usually held so dorsum of body visible. Arranged in 5 – 8 groups on dorso-lateral ridge on each side of body . Translucent white revealing orange, red or reddish brown internal digestive gland and white cnidosac at tip. Anterior and posterior white pigment lines, or series of marks, rise from near base and expand to cover most of cnidosac except extreme apex .
Slightly wrinkled . Translucent white with longitudinal white pigment line from posterior of base to apex, where it expands to often almost completely cap distal quarter of rhinophore.
Long mobile oral tentacles, translucent white with longitudinal white pigment line from apex to head where unites with dorsal body line . Mouthparts ventrally cleft .
Translucent white. Anterior expanded into curved wedge shaped propodial tentacles, often forming crescent in ventral view .
Key identification features
White pigment line along each side, uniting on tail. .
White dorsal line  (sometimes fragmented as on C. browni).
Two white lines, continuous or fragmented, on cerata .
Fjordia chriskaugei Korshunova et al, 2017. Similar to F. lineata, except that opaque white surface pigment on cerata is broken longitudinal lines that do not extend onto the apex to cover the visible internal white cnidosac.
Fjordia browni, Microchlamylla gracilis (Alder & Hancock, 1844), Coryphella verrucosa and Carronella pellucida all lack white lateral body lines and two lines on cerata.Fjordia chriskaugei Korshunova et al, 2017. Similar to F. lineata, except that opaque white surface pigment on cerata is broken longitudinal lines that do not extend onto the apex to cover the visible internal white cnidosac.
Fjordia browni, Microchlamylla gracilis, Coryphella verrucosa and Carronella pellucida all lack white lateral body lines and two lines on cerata.
Ecology and behaviour
Occasionally ELWS on rocky shores exposed to strong currents, can be abundant sublittorally at 20m – 40m, extending to 360m.On or near its prey, primarily Tubularia (EML), but occasionally other hydroids, especially when juvenile.
Simultaneous hermaphrodite. Two or more generations born April-August. Spawn deposited as a white or pink spiral line. Veliger larvae released to drift in the water column before settling and metamorphosing.
Northern Norway to Western Mediterranean. (GBIF map). Occasionally at LWS, and frequent sublittorally, all around Britain and Ireland where Tubularia occurs (UK interactive distribution map NBN).
References and links
Alder, J. & Hancock, A. 1845-1855. A monograph of the British nudibranchiate mollusca. London, Ray Society. Korshunova T, Martynov A, Bakken T, Evertsen J, Fletcher K, Mudianta WI, Saito H, Lundin K, Schrödl M, Picton B (2017) Polyphyly of the traditional family Flabellinidae affects a major group of Nudibranchia: aeolidacean taxonomic reassessment with descriptions of several new families, genera, and species (Mollusca, Gastropoda). ZooKeys 717: 1-139. https://doi.org/10.3897/zookeys.717.21885 Thompson, T.E. & Brown, G.H. 1984. Biology of opisthobranch molluscs 2. London, Ray Society. Current taxonomy; World Register of Marine Species (WoRMS). Irish distribution map and prey organisms Picton, B.E. & Morrow, C.C., 2010. Encyclopedia of Marine Life of Britain and Ireland (EML).