Under tongue weed (Hypoglossum hypoglossoides)

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



A membranous, leafy red seaweed that is rose-pink to brownish red in colour. The thallus consists of blades 2-30 cm high arising singularly or in tuffs from a small disc plate holdfast. The primary fronds are narrow (1-8 mm wide) and have a conspicuous midrib bearing numerous singular or paired lateral blades on both sides that get smaller towards the base of the plant. The end of the fronds are flat, pointed lance-shaped blades and have flat, ruffled or sometimes toothed margins with no lateral veins.

Recorded distribution in Britain and Ireland

Widely distributed and common around the coasts of Britain and Ireland.

Global distribution

Found widely distributed on the coasts of France, Spain, Azores, and the Canaries. Also recorded throughout the Mediterranean. Recorded sporadically off the coast of Kenya, and in the west Atlantic from Carolina to Brazil including the Gulf of Mexico.


It grows on bedrock, stones, pebbles, maerl, crustose corallines and seaweeds, particularly the stipe of Laminaria hyperborea. It is most abundant in Laminaria hyperborea forests and subtidal cliffs. It can be a predominant species in deeper algae communities. It is tolerant to sand scour in a range of conditions from extremely exposed to extremely sheltered sited with strong tidal exposure. 

Depth range

Lower littoral to 30 m

Identifying features

  • Rose pink to brown-red in colour.
  • The main blades are 2-30 cm in length, 1-8 mm wide, with a short cylindrical stripe and conspicuous midrib 0.2-0.8 mm in width.
  • Flat, lance-shaped, ruffled or toothed margined fronds.
  • No lateral veins.
  • Blades are membranous when young but become tough and flexible with age.

Additional information

Hypoglossum hypoglossoides has a characteristic shape but the size of the plant and blades may vary. Plants found in more sheltered areas have a narrower blade width than those in exposed areas. Younger blades are membranous becoming more flexible but tough when older. It grows in the same habitats as Apoglossum ruscifolim with which it can be mistaken. However, Apoglossum ruscifolim is not as common and can also be distinguished by the bright red microscopic lateral veins on the fronds, whereas Hypoglossum hypoglossoides do not have lateral veins. Large specimens of Hypoglossum hypoglossoides may be mistaken as a small specimens of Delesseria sanguinea or Phycodrys rubens but they have large macroscopic veins, which Hypoglossum hypoglossoides do not. 

Listed by

- none -


  1. Bunker, F.StD.P., Brodie, J.A., Maggs, C.A. & Bunker, A.R., 2017. Seasearch Guide to Seaweeds of Britain and Ireland (Second edition). Plymouth: Wild Nature Press.

  2. Fish, J,D., Fish, S., 2011. A Students Guide to the Seashore (Third edition). Cambridge: University press.

  3. Guiry, M.D. & Guiry, G.M. 2015. AlgaeBase [Online], National University of Ireland, Galway [cited 30/6/2015]. Available from: http://www.algaebase.org/

  4. Maggs, C.A. & Hommersand, M.H., 1993. Seaweeds of the British Isles: Volume 1 Rhodophycota Part 3A Ceramiales. London: Natural History Museum, Her Majesty's Stationary Office.


  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: 2024-05-27


This review can be cited as:

Mardle, M.J., 2022. Hypoglossum hypoglossoides Under tongue weed. In Tyler-Walters H. Marine Life Information Network: Biology and Sensitivity Key Information Reviews, [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 27-05-2024]. Available from: https://www.marlin.ac.uk/species/detail/2350

Last Updated: 18/01/2022