Date of introduction and origin
Antithamnionella ternifolia was first recorded in
1906 from Plymouth, Devon (Maggs & Hommersand 1993). This
species was introduced from the southern hemisphere (possibly
Australia), where it is native.
Method of introduction
It was probably carried on the hulls and mooring ropes of
Reasons for success
The species has a rapid growth rate and grows abundantly on
all types of substrata including eelgrass leaves, algae, animals,
pebbles and artificial materials, over a wide range of conditions
(Maggs & Hommersand 1993).
Rate of spread and methods involved
It has spread fairly rapidly around the coast of Britain, from
Plymouth to western Ireland in 30 years (C.A. Maggs pers.
comm.). It spreads mainly through remote (over 30 miles,
through the influence of man) dispersal as it grows on ropes and
It is widely distributed on the south and west coasts of
Britain as far north as Strathclyde (formerly Argyll) in Scotland
(Maggs & Hommersand 1993). There are European populations from
the Netherlands south as far as Portugal.
Factors likely to influence spread and distribution
This species shows a wide temperature tolerance. Sexual
reproduction is rare; the species spreads by fragmentation.
Effects on the environment
No effects are known.
Effects on commercial interests
It is a fouling organism.
Control methods used and effectiveness
More taxonomic research is required to determine whether other
southern hemisphere species are conspecific. In their natural
habitats, Antithamnionella spirographidis and
A.ternifolia are very similar in appearance so microscopic
examination is required to distinguish them.
Maggs, C.A., & Hommersand, M.H. 1993. Seaweeds of the
British Isles. Volume 1: Rhodophyta. Part 3A:
Ceramiales. London, HMSO, for Natural History Museum.
Acknowledgements (contributions from questionnaire)
Dr C.A. Maggs, Queen's University of Belfast.