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Devil's Tongue Weed
Grateloupia turuturu

Last edited: October 2nd 2019

Devil's Tongue Weed - Grateloupia turuturu

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Short description of Grateloupia turuturu, Devil's Tongue Weed

A large red seaweed; deep red to purple in colour, sometimes bleaching to light brown in summer.  One to six elongated, lance-shaped blades up to 15 cm in width and 1m in length arise from a disc holdfast via a short stipe.  The plant is thick and firm with a mucilaginous texture which is slippery to touch.  Also occurs as a crustose form.

Impact summary: Grateloupia turuturu, Devil's Tongue Weed

No impacts have been reported; however, several authors note the potential for this species to displace native seaweeds.  The large, broad blades may shade neighbouring species.

Habitat summary: Grateloupia turuturu, Devil's Tongue Weed

Devil’s tongue weed grows in sheltered areas including harbours and bays, attached to pontoons, harbour walls, shells and stones. It occurs on the lower shore in pools, and subtidally to 7m.  Due to its tolerance of low salinities it may be found in estuarine areas as well as fully marine waters.

Overview table

Environment Marine
Species status Non-Native
Native range Eastern Asia
Functional type Algae (macroalgae)
Status in England Non-Native
Status in Scotland Non-Native
Status in Wales Non-Native
Location of first record Southsea
Date of first record 1973


Devil’s tongue weed is native to Japan and Korea.

First Record

First recorded at Southsea beach in the Solent, in 1969, but misidentified as Grateloupia doryphora.

Pathway and Method

Transport of Pacific oysters for aquaculture is considered the most likely vector of introduction to Europe, although specimens have been recorded attached to vessel’s hulls, suggesting that hull fouling may also be a significant pathway. Spores may also be carried within ships’ ballast water. 

Species Status

Devil’s tongue weed is considered invasive in the Northeast and Northwest Atlantic, Tasmania and New Zealand. On the east coast of North America its range has expanded northwards from Cape Cod by over 130km in less than four years.  Along European Atlantic shores, the rate of spread has been even greater, at 96 km per year.   In parts of the Mediterranean including the Thau Lagoon, France, it is considered common but not invasive.

Dispersal Mechanisms

Fertile blades may drift alone, or attached to small stones may be dispersed by currents or wave action.


Devil’s tongue weed recruits using four different strategies: (1) spores develop into small crusts which give rise to filaments and blades; (2) filaments and/or crusts produce new crusts; (3) new blades develop from old crusts; and (4) blades regenerate from old, damaged blades. Gametangial plants are monoecious (individual plants have separate male and female reproductive structures), and perennial; reproductive cells are recorded throughout the year in GB, with a peak in summer when over 90% of individuals are fertile. 

Known Predators/Herbivores

Herbivorous invertebrates including sea snails.

Resistant Stages

In adverse conditions, devil’s tongue weed can exist in a crustose form which is more resistant to environmental extremes and to grazing.

Habitat Occupied in GB

Devil’s tongue weed grows in sheltered areas including harbours and bays, attached to pontoons, harbour walls, shells and stones. It occurs on the lower shore in pools, and subtidally to 7m.  Due to its tolerance of low salinities it may be found in estuarine areas as well as fully marine waters.

Native range from Japan and Korea. In GB Devil’s tongue weed occurs along the southeast coast of England and in Pembrokeshire, Wales.

Environmental Impact

No ecosystem impacts have been reported in Great Britain; however this large, fast-growing seaweed may have the potential to displace native seaweed species and its large, broad blades may shade neighbouring species.  In North America Devil’s tongue weed is a major competitor of Irish moss (Chondrus crispus) which provides an important winter food source for snails and other invertebrates.  Winter die-back of Devil’s tongue weed may therefore affect local ecology. 

Health and Social Impact

None known.

Economic Impact

None known.


Bunker, F. StP. D, Maggs, C.A., Brodie, J.A. & Bunker, A.R. (2010) Seasearch Guide to Seaweeds of Britain and Ireland. Marine Conservation Society, Ross-on-Wye

Biology, ecology, spread, vectors

Araujo, R., Violante, J., Pereira, R., Abreu, H., Arenas, F. & Sousa-Pinto, I. (2011) Distribution and population dynamics of the introduced seaweed Grateloupia turuturu (Halymeniaceae, Rhodophyta) along the Portuguese coast. Phycologia, 50, (4), 392-402.

Harlin, M.M. & Villalard-Bohnsack, M. (2001) Seasonal dynamics and recruitment strategies of the invasive seaweed Grateloupia doryphora (Halymeniaceae, Rhodophyta) in Narragansett Bay and Rhode Island Sound, Rhode Island, USA. Phycologia, 40, (5), 468-474.

Irvine, L.M. (1983) Seaweeds of the British Isles. Volume 1 Rhodophyta Part 2A Cryptonemiales (sensu stricto) Palmariales, Rhodymeniales.  London: British Museum (Natural) History.

Lyons, D.A. & Scheibling, R.E. (2009) Range expansion by invasive marine algae: rates and patterns of spread at a regional scale. Diversity and Distributions, 15, 762-775.

Mathieson, A.C., Dawes, C.J., Pederson, J., Gladych, R.A. & Carlton, J.T. (2008) The Asian red seaweed Grateloupia turuturu (Rhodophyta) invades the Gulf of Maine. Biological Invasions, 10, 985-988.

Management and impact

D’Archino, R., Nelson, W.A. & Zuccarello, G.C. (2007) Invasive marine red alga introduced to New Zealand waters: First record of Grateloupia turuturu (Halymeniaceae, Rhodophyta). New Zealand Journal of Marine and Freshwater research, 41, (1), 35-42.


Farnham, W.F. (1980) Studies on Aliens in the Marine Flora of Southern England.  In: Price, J.J., Irvine, D.E.G. & Farnham, W.F. (Editors) (1980) The Shore Environment, Volume 2: Ecosystems, pp. 875 – 914. Academic Press, London & New York.

Verlaque, M., Brannock, P.M., Komatsu, T., Villalard-Bohnsack, M. & Marston, M. (2005) The genus Grateloupia C.Agardh (Halymeniaceae, Rhodophyta) in the Thau Lagoon (France, Mediterranean): a case study of marine plurispecific introductions. Phycologia, 44, (5), 477-496.

Wilkes, R.J., McIvor, L.M. & Guiry, M.D. (2005) Using rbcL sequence data to reassess the taxonomic position of some Grateloupia and Dermocorynus species (Halymeniaceae, Rhodophyta) from the north-eastern Atlantic. European Journal of Phycology, 40, (1), 53-60.


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Map of the UK with areas shaded to show the UK distribution

Distribution map

View the Distribution map for Devil's Tongue Weed, Grateloupia turuturu from NBN Atlas