A sea slug (Fjordia lineata)

Distribution data supplied by the Ocean Biodiversity Information System (OBIS). To interrogate UK data visit the NBN Atlas.Map Help



Fjordia lineata is a slender species up to 5 cm in length. Its transluscent body is white with opaque patches and bears 5-8 clusters of approximately 5 elongate cerata along either side of the mantle. The digestive glands in the cerata are reddish-brown or occasionally green and have white opaque tips. The oral tentacles and rhinophores are distinctly long and tapering.This species has numerous characteristic, longitudinal white lines on the body, oral tentacles and rhinophores. The front part of the foot (propodium) is notched and transversely grooved with moderately long tentacles.

Recorded distribution in Britain and Ireland

Common on most of Britain and Ireland, apart from the east coast of England.

Global distribution



Coryphella lineata is a sublittorial species commonly found on its prefered hydroid prey Tubularia indivisa, at 20-40 m depth but reported to 400 m.

Depth range


Identifying features

  • Slender species up to 5 cm in length.
  • Long oral tentacles and rhinophores.
  • Characteristic longitudinal white stripes on:
    • Each side of the body which join at the the rear of the foot (metapodium).
    • A midline on the upper surface which divides and continues on to the oral tentacles.
    • Both of the rhinophores.
    • The sides of each ceras which also bear an opaque white tip.
  • Translucent white body with opaque patches.
  • 5-8 clusters of ca. 5 cerata on the upper surface.
  • Cerata are white tipped and reddish-brown or occasionally green.

Additional information

Fjordia lineata lays its eggs in a spiralling ribbon-like white or pink mass. The eggs hatch into planktonic larvae. Egg ribbons are usually laid on their prey, principally the hydroid Tubularia indivisa. This species may also feed on Corymorpha nutans, Hydrallmania falcata, Coryne spp., or Sertularia spp. The occasional green colouration of the digestive gland in the cerata may be due to starvation (Thompson, 1988).

This species is very similar to other Fjordia species epecially as it can be found with Fjordia browni in large numbers. However, it is distinguished from other species by the distinct white lines.

Listed by

- none -


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  1. NBN (National Biodiversity Network) Atlas. Available from: https://www.nbnatlas.org.

  2. OBIS (Ocean Biodiversity Information System),  2024. Global map of species distribution using gridded data. Available from: Ocean Biogeographic Information System. www.iobis.org. Accessed: 2024-05-20


This review can be cited as:

Rowley, S.J. 2007. Fjordia lineata A sea slug. In Tyler-Walters H. and Hiscock K. Marine Life Information Network: Biology and Sensitivity Key Information Reviews, [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 20-05-2024]. Available from: https://www.marlin.ac.uk/species/detail/2195

Last Updated: 15/02/2007