''Codium fragile'', known commonly as green sea fingers, dead man's fingers, felty fingers,
Intertidal Organisms EZ ID Guides. Island County Beachwatchers. Washington State University Extension. 2006. forked felt-alga, stag seaweed, sponge seaweed,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). green sponge, green fleece, and oyster thief,
Aquatic Invasive Species. Fisheries and Oceans Canada. is a species of

seaweed Seaweed, or macroalgae, refers to thousands of species of macroscopic, multicellular, marine algae. The term includes some types of ''Rhodophyta'' (red), ''Phaeophyta'' (brown) and ''Chlorophyta'' (green) macroalgae. Seaweed species such as ke ...

in the family Codiaceae. It originates in the

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the contine ...

near Japan and has become an

invasive species An invasive species otherwise known as an alien is an introduced organism that becomes overpopulated and harms its new environment. Although most introduced species are neutral or beneficial with respect to other species, invasive species adv ...

on the coasts of the Northern

Atlantic Ocean The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth#Surface, Earth's surface and about 29% of its water surface area. It is known to separate the "Old World" of Afr ...

Description

This siphonous

green alga The green algae (singular: green alga) are a group consisting of the Prasinodermophyta and its unnamed sister which contains the Chlorophyta and Charophyta/ Streptophyta. The land plants ( Embryophytes) have emerged deep in the Charophyte alg ...

is of two subspecies in

Great Britain Great Britain is an island in the North Atlantic Ocean off the northwest coast of continental Europe. With an area of , it is the largest of the British Isles, the largest European island and the ninth-largest island in the world. It is ...

and

Ireland Ireland ( ; ga, Éire ; Ulster Scots dialect, Ulster-Scots: ) is an island in the Atlantic Ocean, North Atlantic Ocean, in Northwestern Europe, north-western Europe. It is separated from Great Britain to its east by the North Channel (Grea ...

. 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 (micrometre) long.Burrows,E.M. 1991. ''Seaweeds of the British Isles''. Natural History Museum, London The rounded tips of these closely packed utricles give the frond a velvety texture. The fronds hang down from rocks during low tide, hence the nickname "dead man's fingers". The "fingers" are branches up to a centimeter wide and sometimes over 30 centimeters long. ''Codium fragile'' occurs in the low

intertidal zone The intertidal zone, also known as the foreshore, is the area above water level at low tide and underwater at high tide (in other words, the area within the tidal range). This area can include several types of habitats with various species ...

, and subtidal on high-energy beaches. It has no

gametophyte A gametophyte () is one of the two alternation of generations, alternating multicellular organism, multicellular phases in the life cycles of plants and algae. It is a haploid multicellular organism that develops from a haploid spore that has on ...

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. ''Codium fragile'' subsp. ''atlanticum'' is known to have arrived in the southwest of

around 1808. From there it may have spread by rafting or floating in the sea. Approximately 30 years later, it was found in

Scotland Scotland (, ) is a country that is part of the United Kingdom. Covering the northern third of the island of Great Britain, mainland Scotland has a border with England to the southeast and is otherwise surrounded by the Atlantic Ocean to th ...

. It is thought to have originally come from the

near Japan. Since 1840, when it was first discovered in Scotland, it has spread the entire length of Britain, including

Shetland Shetland, also called the Shetland Islands and formerly Zetland, is a subarctic archipelago in Scotland lying between Orkney, the Faroe Islands and Norway. It is the northernmost region of the United Kingdom. The islands lie about to the ...

. Between 1949 and 1955 it is known to have spread between

Berwick-upon-Tweed Berwick-upon-Tweed (), sometimes known as Berwick-on-Tweed or simply Berwick, is a town and civil parish in Northumberland, England, south of the Anglo-Scottish border, and the northernmost town in England. The 2011 United Kingdom census recor ...

and

St. Andrews St Andrews ( la, S. Andrea(s); sco, Saunt Aundraes; gd, Cill Rìmhinn) is a town on the east coast of Fife in Scotland, southeast of Dundee and northeast of Edinburgh. St Andrews had a recorded population of 16,800 , making it Fife's fourt ...

Fife Fife (, ; gd, Fìobha, ; sco, Fife) is a council area, historic county, registration county and lieutenancy area of Scotland. It is situated between the Firth of Tay and the Firth of Forth, with inland boundaries with Perth and Kinross ...

, 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 ) , motto= ( en, "Rather die free than subjected in peace") , anthem=( en, "Anthem of the Azores") , image_map=Locator_map_of_Azores_in_EU.svg , map_alt=Location of the Azores within the European Union , map_caption=Location of the Azores wi ...

. This species displaces the native '' Codium tomentosum''. ''Codium fragile'' subsp. ''atlanticum'' is used as food in the

Far East The ''Far East'' was a European term to refer to the geographical regions that includes East and Southeast Asia as well as the Russian Far East to a lesser extent. South Asia is sometimes also included for economic and cultural reasons. The te ...

.''Codium fragile'' ssp. ''atlanticum''.
Joint Nature Conservation Committee, UK. Codium fragile (Suringar) Hariot, 1889

''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. The subspecies ''Codium fragile'' subsp. ''tomentosoides'' (syn. ''Codium mucronatum'' var. ''tomentosoides''), occurs along nearly the whole coastline of the eastern

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., federal district, five ma ...

, from the

Gulf of St. Lawrence The Gulf of St. Lawrence () is the outlet of the North American Great Lakes via the St. Lawrence River into the Atlantic Ocean. The gulf is a semi-enclosed sea, covering an area of about and containing about of water, at an average depth of . ...

in Canada to

North Carolina North Carolina () is a state in the Southeastern region of the United States. The state is the 28th largest and 9th-most populous of the United States. It is bordered by Virginia to the north, the Atlantic Ocean to the east, Georgia a ...

. It is a rapidly spreading invasive species. It originated in the

around Japan, and was introduced into

New York New York most commonly refers to: * New York City, the most populous city in the United States, located in the state of New York * New York (state), a state in the northeastern United States New York may also refer to: Film and television * '' ...

from

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a subcontinent of Eurasia and it is located enti ...

in 1957. Its presence was first recorded in 1964 in the

Gulf of Maine , image = , alt = , caption = , image_bathymetry = GulfofMaine2.jpg , alt_bathymetry = , caption_bathymetry = Major features of the Gulf of Maine , location = Northeast coast of the ...

at Boothbay. It is now recorded around

.Morton, O. 2003. The marine macroalgae of County Donegal, Ireland. ''Bulletin of Ireland biogeography Society'' No 27: 3 – 164 It has also been recorded from the Scilly Isles, the

Channel Islands The Channel Islands ( nrf, Îles d'la Manche; french: îles Anglo-Normandes or ''îles de la Manche'') are an archipelago in the English Channel, off the French coast of Normandy. They include two Crown Dependencies: the Bailiwick of Jersey ...

, and the south and west coasts of

England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe ...

and

. 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 Shellfish is a colloquial and fisheries term for exoskeleton-bearing aquatic invertebrates used as food, including various species of molluscs, crustaceans, and echinoderms. Although most kinds of shellfish are harvested from saltwater env ...

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".

''Codium fragile'' subsp. ''scandinavicum''

This subspecies was introduced from Asiatic coasts of the Pacific to Norway, and to

Denmark ) , song = ( en, "King Christian stood by the lofty mast") , song_type = National and royal anthem , image_map = EU-Denmark.svg , map_caption = , subdivision_type = Sovereign state , subdivision_name = Kingdom of Denmark , establishe ...

in 1919.

''Codium fragile'' subsp. ''novae-zelandiae''

This subspecies is found in the low intertidal to subtidal zones around

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 List of islands of New Zealand, smaller islands. It is the ...

at the North Island, South Island, Chatham Islands, Stewart Island, Auckland Island, Campbell Island as well as around the

Falkland Islands The Falkland Islands (; es, Islas Malvinas, link=no ) is an archipelago in the South Atlantic Ocean on the Patagonian Shelf. The principal islands are about east of South America's southern Patagonian coast and about from Cape Dubou ...

References

{{Taxonbar, from=Q2712208 fragile Edible seaweeds