Codium fragile

Codium fragile, known commonly as green sea fingers, dead man's fingers, felty fingers,[1] forked felt-alga, stag seaweed,[2] sponge seaweed,[3] green sponge,[4] green fleece,[5] sea staghorn,[6] and oyster thief,[7] is a species of seaweed in the family Codiaceae. It originates in the Pacific Ocean near Japan and has become an invasive species on the coasts of the Northern Atlantic Ocean.

Codium fragile
Codium fragile on the Massachusetts coast
Scientific classification Edit this classification
(unranked): Viridiplantae
Division: Chlorophyta
Class: Ulvophyceae
Order: Bryopsidales
Family: Codiaceae
Genus: Codium
Species:
C. fragile
Binomial name
Codium fragile
(Suringar) Hariot

Description

This siphonous green alga is of two subspecies in Great Britain and Ireland. They are similar, both are dark green in color. It forms long erect finger-like fronds. These grow to 40 cm or more long branching dichotomously. The cortex of the branches is formed by closely packed utricles, these are small cylindrical club-shaped structures formed from a single cell up to 1200 µm (micrometres) long.[8] The rounded tips of these closely packed utricles give the frond a velvety texture.[9] The fronds hang down from rocks during low tide, hence the nickname "dead man's fingers".[10] The "fingers" are branches up to a centimeter wide and sometimes over 30 centimeters long.

Codium fragile occurs in the low intertidal zone, and subtidal on high-energy beaches.

It has no gametophyte stage, and male and female gametes are both produced on separate plants.

Subspecies

Subspecies of C. fragile can only be distinguished microscopically.

Codium fragile subsp. atlanticum

This subspecies can be distinguished by the mucron or tip of the utricles. In this subspecies the mucron is short, no more than 20 µm long.[8]

Codium fragile subsp. atlanticum is known to have arrived in the southwest of Ireland around 1808. From there it may have spread by rafting or floating in the sea. Approximately 30 years later, it was found in Scotland. It is thought to have originally come from the Pacific Ocean near Japan.

Since 1840, when it was first discovered in Scotland, it has spread the entire length of Britain, including Shetland. Between 1949 and 1955 it is known to have spread between Berwick-upon-Tweed and St. Andrews, Fife, a distance of 80 km. Populations of this algae occur mostly in northern Britain. Elsewhere in Europe it is found in several places, including Norway, Netherlands, France, Spain and the Azores.

This species displaces the native Codium tomentosum.

Codium fragile subsp. atlanticum is used as food in the Far East.[11]

Close-up

Codium fragile subsp. tomentosoides

This subspecies is distinguished from C.fragile subsp. atlanticum by its very pointed mucron (the tip of the utricle) – up to µm 68 long.[8]

The subspecies Codium fragile subsp. tomentosoides[12][13] (syn. Codium mucronatum var. tomentosoides), occurs along nearly the whole coastline of the eastern United States, from the Gulf of St. Lawrence in Canada to North Carolina. It is a rapidly spreading invasive species.[1] It originated in the Pacific Ocean around Japan, and was introduced into New York from Europe in 1957. Its presence was first recorded in 1964 in the Gulf of Maine at Boothbay. It is now recorded around Ireland.[14] It has also been recorded from the Scilly Isles, the Channel Islands, and the south and west coasts of England and Scotland.[8]

This is a dominant subspecies in the subtidal zone, attaching to almost any hard surface. This results in increased maintenance labor for aquaculturists and reduces the productivity of cultured marine life. In established shellfish beds, this species can become a nuisance; it may attach to shellfish and then float away, carrying the animals with it. This was the inspiration for the common name "oyster thief".[7]

Codium fragile subsp. scandinavicum

This subspecies was introduced from Asiatic coasts of the Pacific to Norway, and to Denmark in 1919.[11]

Codium fragile subsp. novae-zelandiae

This subspecies is found in the low intertidal to subtidal zones around New Zealand at the North Island, South Island, Chatham Islands, Stewart Island, Auckland Island, Campbell Island as well as around the Falkland Islands.[15]

References
Wikimedia Commons has media related to Codium fragile.
  1. Codium fragile (Dead man's fingers, felty fingers). Archived 27 July 2011 at the Wayback Machine Intertidal Organisms EZ ID Guides. Island County Beachwatchers. Washington State University Extension. 2006.
  2. Invasive Species in the Pacific Northwest, P. Dee Boersma, Sarah H. Reichard, Amy N. Van Buren, 2006, ISBN 978-0-29598596-1, 208 at Google Books
  3. Guiry, M. D. Codium fragile (Suringar) Hariot, 1889. In: Guiry, M.D. & G. M. Guiry. (2013). AlgaeBase. National University of Ireland, Galway. Accessed through: World Register of Marine Species (WoRMS).
  4. Codium fragile ssp. tomentosoides (Dead Man's Fingers). Archived 17 July 2012 at archive.today Marine Invasive Species in Nova Scotia. Benthic Ecology Lab, Dalhousie University. 2001.
  5. Costa, J. Codium algae population explosion in Wareham. Archived 4 March 2016 at the Wayback Machine Buzzards Bay National Estuary Program.
  6. "Sea staghorn • Codium fragile". Biodiversity of the Central Coast. Retrieved 10 July 2023.
  7. Oyster Thief (Codium fragile spp. fragile). Archived 13 November 2013 at the Wayback Machine Aquatic Invasive Species. Fisheries and Oceans Canada.
  8. Burrows,E.M. 1991. Seaweeds of the British Isles. Natural History Museum, London ISBN 0-565-00981-8
  9. Dickinson, C.I. 1963 British Seaweeds. The Kew Series, Eyre & Spottiswoode
  10. Codium fragile: Dead Man's Fingers. Archived 16 May 2011 at the Wayback Machine Monterey Bay Aquarium Research Institute. 1996.
  11. Codium fragile ssp. atlanticum. Joint Nature Conservation Committee, UK.
  12. Codium fragile ssp. tomentosoides. Archived 4 March 2016 at the Wayback Machine Global Invasive Species Database. ISSG.
  13. Codium fragile ssp. tomentosoides. Introduced Species: Descriptions. MIT Sea Grant.
  14. Morton, O. 2003. The marine macroalgae of County Donegal, Ireland. Bulletin of Ireland biogeography Society No 27: 3 – 164
  15. W. A., Nelson (2013). New Zealand seaweeds : an illustrated guide. Wellington, New Zealand: Te Papa Press. p. 30. ISBN 9780987668813. OCLC 841897290.
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