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Rhodophyta, Red Algae

Nemalion helminthoides (Velley) Batters

Rhodophyta, Order: Nemaliales; Family: Liagoraceae=Nemalionaceae. Nema means a ‘thread’ or a ‘filament’, and helminthoid means ‘worm-shaped’, referring to its elongated and smooth thallus.


The Nemalion helminthoides is a brown, mucousy, elongated and twisted alga that resembles a shoelace or spaghetti. Its holdfast clings to rock, and several filaments emanate from it. On rare occasions, dichotomous branching may be observed in the thallus.


The algal length ranges from several centimeters to 40 cm, and its width ranges between 1-6 mm.


The Nemalion helminthoides is brown, usually dark.

Special features

The algal mucousy appearance resembles a brown filament of spaghetti. Its habitat is the upper regions of the abrasion platform, facing the sea. The width varies, as does the shade and texture of individuals, but the thalli on every individual are identical.


The Nemalion helminthoides grows at the upper reaches of the intertidal zone on the edge of the abrasion platform, in an upper area that usually forms the rim of the tidal pool (often in an area built by and populated by Serpula sp.). Often, the Nemalion helminthoides is the only macro alga in the near vicinity, and its appearance in an area free of other algae is pertinent, since the area would otherwise be the site of competition. The species’ ‘loneliness’ may be the result of either arresting substances that the alga secretes, which inhibit the colonization by other species, or due to the preference of herbivores that, for some reason, do not eat this specific alga. There may be other reasons. Without doubt, this does pose a fascinating subject for research. The Nemalion helminthoides is exposed to the air most of the time.

Biology and reproduction

The outer layer of cells is rich in pigmentation, and the inner ones are colourless. The Nemalion helminthoides is monoecious. The male and female reproductive cells (gametes) are generated in the same individual. Research into the induction of reproductive cell generation in Nemalion reveals that the production of reproductive cells is affected by environmental conditions, especially day length. The ability to control the reproductive mechanism is important, if for no other reason than the Nemalion helminthoides’ economic importance as a source of agar.

Seasonality and distribution

The Nemalion helminthoides can be found along rocky beaches for a short period in Spring and early Summer.

Additional species

An additional species of Nemalion reported in the Eastern Mediterranean is Nemalion multifidum (Weber and Mohr)

J. Agardh, mostly noted in Turkey. Nemalion multifidum differs from the above in its higher level of branching. Some researchers claim that the characteristic is not significant, and that this is actually the same species. Nemalions are marketed as consumables in Japan and in Western organic food outlets, where imports from the Far East are sold. Since the alga can be found in the Mediterranean and is quite tasty, one may expect it eventually to be produced for consumption here, as well.

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