Page 36 - Invasive_Species_2013

Mediterranean invasive species factsheet

ALGAE

Reproduction Common name: not assigned

Terminal
gland cells
identification

Scientific Name: Whorl
Acrothamnion preissii branchlets
Picture

Key identifying features

Clumps of loose algae, rose-red in colour and highly Brief history
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.

Field identification signs and habitat
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
Acrothamnion preissii. Photo: E. Ballesteros
entrances and crevices).

Acrothamnion preissii. Photo: B. Weitzmann Acrothamnion preissii. Photo: B. Weitzmann

Monitoring Marine Invasive Species in Mediterranean MPAs: A strategy and practical guide for managers 33