''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, sea staghorn, 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 ...

in the family

Codiaceae Codiaceae is a family (biology), family of green algae in the order Bryopsidales. Genera * † ''Abacella'' Maslov * † ''Appeninocodium'' O.Dragastan * † ''Arabicodium'' G.F.Elliott * ''Bevocastria'' E.J.Garwood * ''Botryella'' V.P.Shu ...

. It originates in the

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

near Japan and has become an

invasive species An invasive species is an introduced species that harms its new environment. Invasive species adversely affect habitats and bioregions, causing ecological, environmental, and/or economic damage. The term can also be used for native spec ...

on the coasts of the Northern

Atlantic Ocean The Atlantic Ocean is the second largest of the world's five borders of the oceans, oceanic divisions, with an area of about . It covers approximately 17% of Earth#Surface, Earth's surface and about 24% of its water surface area. During the ...

Description

This siphonous

green alga The green algae (: green alga) are a group of chlorophyll-containing autotrophic eukaryotes consisting of the phylum Prasinodermophyta and its unnamed sister group that contains the Chlorophyta and Charophyta/ Streptophyta. The land plants ( ...

is of two subspecies in

Great Britain Great Britain is an island in the North Atlantic Ocean off the north-west coast of continental Europe, consisting of the countries England, Scotland, and Wales. With an area of , it is the largest of the British Isles, the List of European ...

and

Ireland Ireland (, ; ; Ulster Scots dialect, Ulster-Scots: ) is an island in the North Atlantic Ocean, in Northwestern Europe. Geopolitically, the island is divided between the Republic of Ireland (officially Names of the Irish state, named Irelan ...

. 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 The micrometre (English in the Commonwealth of Nations, Commonwealth English as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer (American English), also commonly known by the non-SI term micron, is a uni ...

s) 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 or foreshore is the area above water level at low tide and underwater at high tide; in other words, it is the part of the littoral zone within the tidal range. This area can include several types of habitats with various ...

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

gametophyte A gametophyte () is one of the two alternating multicellular phases in the life cycles of plants and algae. It is a haploid multicellular organism that develops from a haploid spore that has one set of chromosomes. The gametophyte is the se ...

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 Countries of the United Kingdom, country that is part of the United Kingdom. It contains nearly one-third of the United Kingdom's land area, consisting of the northern part of the island of Great Britain and more than 790 adjac ...

. It is thought to have originally come from the

near

Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...

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

Shetland Shetland (until 1975 spelled Zetland), also called the Shetland Islands, is an archipelago in Scotland lying between Orkney, the Faroe Islands, and Norway, marking 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,

Fife Fife ( , ; ; ) is a council areas of Scotland, council area and lieutenancy areas of Scotland, lieutenancy area in Scotland. A peninsula, it is bordered by the Firth of Tay to the north, the North Sea to the east, the Firth of Forth to the s ...

, 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 The Azores ( , , ; , ), officially the Autonomous Region of the Azores (), is one of the two autonomous regions of Portugal (along with Madeira). It is an archipelago composed of nine volcanic islands in the Macaronesia region of the North Atl ...

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

Far East The Far East is the geographical region that encompasses the easternmost portion of the Asian continent, including North Asia, North, East Asia, East and Southeast Asia. South Asia is sometimes also included in the definition of the term. In mod ...

.''Codium fragile'' ssp. ''atlanticum''.
Joint Nature Conservation Committee, UK.

''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 (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

, from the Gulf of St. Lawrence in Canada to

North Carolina North Carolina ( ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It is bordered by Virginia to the north, the Atlantic Ocean to the east, South Carolina to the south, Georgia (U.S. stat ...

. 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 (state), a state in the northeastern United States * New York City, the most populous city in the United States, located in the state of New York New York may also refer to: Places United Kingdom * ...

from

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

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

Gulf of Maine The Gulf of Maine is a large gulf of the Atlantic Ocean on the east coast of North America. It is bounded by Cape Cod at the eastern tip of Massachusetts in the southwest and by Cape Sable Island at the southern tip of Nova Scotia in the northea ...

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 Isles of Scilly ( ; ) are a small archipelago off the southwestern tip of Cornwall, England. One of the islands, St Agnes, is over farther south than the most southerly point of the British mainland at Lizard Point, and has the souther ...

, the

Channel Islands The Channel Islands are an archipelago in the English Channel, off the French coast of Normandy. They are divided into two Crown Dependencies: the Jersey, Bailiwick of Jersey, which is the largest of the islands; and the Bailiwick of Guernsey, ...

, and the south and west coasts of

England England is a Countries of the United Kingdom, country that is part of the United Kingdom. It is located on the island of Great Britain, of which it covers about 62%, and List of islands of England, more than 100 smaller adjacent islands. It ...

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, in colloquial and fisheries usage, are exoskeleton-bearing Aquatic animal, aquatic invertebrates used as Human food, food, including various species of Mollusca, molluscs, crustaceans, and echinoderms. Although most kinds of 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".

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

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

Denmark Denmark is a Nordic countries, Nordic country in Northern Europe. It is the metropole and most populous constituent of the Kingdom of Denmark,, . also known as the Danish Realm, a constitutionally unitary state that includes the Autonomous a ...

in 1919.

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

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

New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...

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

Falkland Islands The Falkland Islands (; ), commonly referred to as The Falklands, 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 from Cape Dub ...

References

{{Taxonbar, from=Q2712208 fragile Edible seaweeds Protists described in 1889 Chlorophyta species