Chorda filum is a brown seaweed with long cord-like fronds, only 5 mm thick in diameter. The fronds are hollow, slippery, unbranched and grow up to 8 m long. The species attaches to the substratum using a small discoid holdfast. It is an annual species, disappearing in winter. 

Original publication: Stackhouse, J. (1797). Nereis britannica; continens species omnes fucorum in insulis britannicis crescentium: descriptione latine et anglico, necnon iconibus ad vivum depictis... Fasc. 2. pp. ix-xxiv, 31-70, pls IX-XIII. Bathoniae [Bath] & Londini [London]: S. Hazard; J. White.

 Download PDF from Algaebase

Chorda filum has typically long, unbranched and hollow rope- or cord-like brown fronds about 0.5 centimeters in diameter but can reach to lengths of 4 to 5 meters, and even up to 8 meters in some locations. The adult frond is a hollow tube, the walls of which are spirally constructed. The frond is frequently inflated with gases in air pockets in the terminal region, causing the thallus to float toward the surface. The end of the frond decays continuously and is replaced by growth from a sub-terminal meristem. Chorda filum is typically yellowish brown to dark brown, with colorless short hairs on the frond in summer, which are sparse or absent on older plants. The species occurs in clumps, attached to the unstable substratum such as pebbles, stones, and shells using a small discoid holdfast which is often buried in the sand. Chorda filum can also grow as an epiphyte on other macroalgae such as Fucus vesiculosus and on Zostera marina (eelgrass).

Chorda filum is most commonly found in sheltered bays, estuaries, lagoons and sea lochs in rock pools on the low shore and in the sublittoral down to 5 meters, where there is a slight current. It has been noted to grow in depths of 30 meters in the Mediterranean. It is rarely found on the open coast and is completely absent from exposed shores. During stormy weather, plants may be washed to more sheltered locations where they continue development. Chorda filum has considerable tolerance to reduced salinities and extends into river mouths. However, plants that grow in fully marine conditions cannot withstand immersion in freshwater. Chorda filum is a summer annual species, falling into decay in the autumn, and disappearing in winter, and can reach a growth rate of 17 centimeters per month during the summer.

Link for Seaweed Industry Association

Abundant throughout the North Atlantic, on the shores of Europe and America. Coast of Brazil. Also in the North Pacific, at Sitka, Unalaschka and Kamtschatka.

Chorda filum is widespread in the temperate waters of the northern hemisphere. It can be found in the Canadian Arctic, and in the Northwest Atlantic from Labrador to New Jersey. In the Northeast Atlantic, Chorda filum can be seen from the Baltic Sea to the Canary Islands, including Spain, Portugal, France, the English Channel, most coasts of England and Ireland, Greenland, Iceland, the Faroes. It is also in the North Sea, including Spitsbergen, Norway, Sweden, Denmark, The Netherlands, Belgium, and into the Baltic Sea, and also the Mediterranean. It is found in the North Pacific, from the Bering Straits to the Kuril Islands, China, and Japan, and to Prince William Sound in Alaska in North America.

Direct use as food - food, consumed whole

Miscellaneous uses (aesthetic, traditional) - String

Provide biological, medical and pharmacological activity - antimicrobial

Source of hydrocolloids - source of alginate

Terrestrial plant and animal production - animal feed (additive)

See other uses in this link

Chorda filum is used fresh as a foodstuff, and is available from a seller in Ireland.

Kawai, H., Sasaki, H., Maeda, Y. & Arai, S. (2001). Morphology, life history, and molecular phylogeny of Chorda rigida, sp. nov. (Laminariales, Phaeophyceae) from the Sea of Japan and the genetic diversity of Chorda filum. Journal of Phycology 37: 130-142.

Lane, C.E., Mayes, C., Druehl, L.D. & Saunders, G.W. (2006). A multi-gene molecular investigation of the kelp (Laminariales, Phaeophyceae) supports substantial taxonomic re-organization. Journal of Phycology 42: 493-512.

Lindeberg, M.R. & Lindstrom, S.C. (2010). Field guide to the seaweeds of Alaska. pp. [i-]iii-iv, 1-188, numerous col. photographs. Fairbanks: Alaska Sea Grant College Program.

Loiseaux-de Goër, S. & Noailles, M.-C. (2008). Algues de Roscoff. pp. [1]-215, col. figs. Roscoff: Editions de la Station Biologique de Roscoff.

Sasaki, H. & Kawai, H. (2007). Taxonomic revision of the genus Chorda (Chordaceae, Laminariales) on the basis of sporophyte anatomy and molecular phylogeny. Phycologia 46: 10-21.

In English: Sea Lace; Dead man's rope; Mermaid's tresses; Cat gut

In Japanese: Tsuru-mo

In German: Meersaite

In French: Fil de Mer

Other names: Bootlace weed, cat gut, cat's gut, dead man's rope, dead man's ropes, fil de mer, gemeine Meersaite, jouhilevä, lacet, lacet de mer, Meersaite, mermaid's fishing line, mermaid's tresses, roccálach, ruadhálach, ruálach, sea lace, seatwine, Skollathvengur, spaghetti kelp, strengetang, sudare, sznureczek witkowaty, veterwier.

Type species: This is the type species (holotype) of the genus Chorda

Basionym: Fucus filum Linnaeus

Type locality: “in Oceano Atlantico” (Athanasiadis 1996: 207).