Chorda filum
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.

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.

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. It may be common or abundant near low water and in the sublittoral to  areas in mud and sand.

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.

References

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Laminariales
Protists described in 1753
Taxa named by John Stackhouse
Brown algae species