Scientific Name:

Acrothamnion preissii

Common Name:
No common name
Taxonomic Group:
Algae

Information

Clumps of loose algae, rose-red in colour and highly branched, 0.5–1.5 cm long, forming dense monospecific mats up to 1 cm thick. The thallus is attached to the substrate or other algae by rhizoids.

The species can only be identified under a binocular microscope. Consequently, accurate identification might need to be checked by a specialist in this group.

Central cells are cylindrical, without cortication; main branches measure 150–300 µm long and 40–60 µm wide. In general, each central cell produces 3–4 lateral branches distally. Terminal gland cells, observed at the end of most branches, are transversely ovoid, 16–22 µm in diameter.

Often found as an epiphyte on sea grasses such as Posidonia oceanica or various algae, from shallow subtidal zones to depths of nearly 40 m. As an invasive species, it forms dense cotton-wool-like tufts, mostly in dim light conditions (i.e. on Posidonia oceanica rhizomes, in maerl beds, or in cave entrances and crevices).

In the Mediterranean Sea only vegetative reproduction is known and no fertile specimens have been found.

Although it can easily be confused with other filamentous red algae (i.e. Womersleyella setacea) when directly observed in the field, the presence of terminal gland cells at the end of most branches is a useful character for identifying Acrothamnion preissii.

Acrothamnion preissii Similar Species (0010) EN
Womersleyella setacea

An Indo-Pacific species native to Western Australia, New Zealand, South Africa and Japan that has probably been introduced into Europe by maritime transport (on ship hulls). At present, it is mainly distributed in the north-western Mediterranean, forming invasive populations in France, Italy, Monaco and Spain.

Ecological impacts of the red alga Acrothamnion preissii are still largely unknown but, when invasive, it becomes dominant outcompeting or replacing most native algal species.

Unknown.

Once it has become invasive, eradication and even containment are not possible. The species might be controlled most efficiently and effectively, and at the lowest cost, early in the invasive process.

Ferrer, E., et al. 1994. The spread of Acrothamnion preissii (Sonder) Wollaston (Rhodophyta , Ceramiaceae) in the Mediterranean Sea: New record from the Balearic Islands. Fl. Medit. 4, 163-166.

Klein, J.C. & Verlaque, M., 2011. Macroalgae newly recorded, rare or introduced to the French Mediterranean coast. Cryptogamie Algologie 31(2), 111-130.

Piazzi,l. & F. Cinelli., 2000. Effects of expansion of introduced Rhodophyceae Acrothamnion preisii and Womersleyella setacea on the algal communites of Posidonia oceanica rhizomes in the western Mediterranean. Cryptogam. Algol., 21(3): 291-300.

Image
Acrothamnion preissii Illustration

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