Chorda filum, commonly known as dead man's rope or sea lace among other names, is a species of brown algae in the genus Chorda. It is widespread in the temperate waters of the northern hemisphere. The species has numerous other common names related to its physical appearance. These include mermaid's tresses, cat's gut or sea-catgut, bootlace weed, sea-twine, and mermaid's fishing line.
Cultivation
In the spring of 2025, a groundbreaking breakthrough was made in the cultivation of this type of seaweed: for the first time, it was successfully grown using spore propagation. The work, carried out by the Danish company Dansk Tang, marks a historic step forward in enabling seaweed farming in environments with lower salinity than previously thought possible.
Description
Chorda filum have typically long, unbranched and hollow rope-like brown fronds about in diameter but can reach to lengths of . The holdfast is disc-shaped. C. filum is found in sheltered marine and estuarine bodies of water at depths of up to . They are usually anchored to loose substrates like gravel and pebbles or other macroalgae and eelgrass. C. filum grow at an average of per month, with the spiral-shaped, often gas-inflated, termini of fronds being dead, but receiving replacement by growth from a sub-terminal meristem. They are annuals, and die during winter. The fronds bear short colorless hairs in summer.Bunker, F. StP. D, Maggs, C.A., Brodie, J.A., Bunker, A. 2017 Seaweeds of Britain and Ireland. Second Edition. Wild Nature Press, Plymouth, UK
Chorda filum is similar to Halosiphon tomentosus. However H. tomentosus is less common and is covered with long brown paraphyses or sterile hairs.
Habitat Chorda filum is to be found in very sheltered shores.Lewis, J.R. 1964 The Ecology of Rocky Shores. The English Universities Press Ltd, London It may be common or abundant near low water and in the sublittoral to areas in mud and sand.Morton, O. 1994. Marine Algae of Northern Ireland. Ulster Museum, Belfast Morton, O. 2003 The marine macroalgae of County Donegal, Ireland. Bulletin of the Irish Biogeographical Society No. 27
Distribution Chorda filum is found in temperate waters in the northern hemisphere, on the coasts of the northern Atlantic and Pacific oceans. Within this, it is noted as being widespread and generally common around Ireland, Great Britain, the Shetland Isles, and the Isle of Man.Hardy, F.G. and Guiry, M.D. 2003 A Check-list and Atlas of Seaweeds of Britain and Ireland. The British Phycological Society,
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