''Alcyonium digitatum'' or dead man's fingers is a

species In biology, a species is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of ...

soft coral Alcyonacea, or soft corals, are an order of corals. In addition to the fleshy soft corals, the order Alcyonacea now contains all species previously known as "gorgonian corals", that produce a more or less hard skeleton, though quite different f ...

in the family Alcyoniidae. It is found around the coasts of the northern Atlantic Ocean and other temperate waters such as the South Pacific.

Description

Dead man's fingers is a colonial coral forming clumps of yellow, white or cream-coloured fleshy masses of finger-like lobes. The surface layer include many

sclerite A sclerite ( Greek , ', meaning " hard") is a hardened body part. In various branches of biology the term is applied to various structures, but not as a rule to vertebrate anatomical features such as bones and teeth. Instead it refers most commonl ...

s which form a crust. The individual polyps are white and translucent, and project from the leathery surface when feeding, giving the colony a furry appearance.Encyclopedia of Marine Life of Britain and Ireland
/ref>

Distribution and habitat

Dead man's fingers is found along the Atlantic coasts of north west Europe from Portugal to Norway, most recently being discovered in the unchartered waters of Jammerbugt bay off the north-west coast of Denmark by a 2020 seafloor mapping project led by explorer Klaus Thymann. The species also occurs in parts of Canada, northeastern coast of the United States, 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 ...

and the

Bay of Fundy The Bay of Fundy (french: Baie de Fundy) is a bay between the Canadian provinces of New Brunswick and Nova Scotia, with a small portion touching the U.S. state of Maine. It is an arm of the Gulf of Maine. Its extremely high tidal range is th ...

and the northern waters of New Zealand.World Register of Marine Species
/ref> The polyps live in colonies attached to bedrock, boulders, stones and occasionally the shells of crabs and gastropods. They are most plentiful in areas with strong water movement and where there is insufficient sunlight for algae to predominate. They are usually found in the

sublittoral zone The neritic zone (or sublittoral zone) is the relatively shallow part of the ocean above the drop-off of the continental shelf, approximately in depth. From the point of view of marine biology it forms a relatively stable and well-illuminated ...

down to about fifty metres. This coral is common around the coasts of Britain and Ireland where ''

Alcyonium glomeratum ''Alcyonium glomeratum'' or red sea fingers is a species of Alcyonacea, soft coral in the family Alcyoniidae. It is found around the southern and western coasts of Great Britain, Britain and Ireland. Description Red sea fingers is similar in sha ...

'' and '' Alcyonium hibernicum'' are also found but these are much rarer and misidentification is unlikely.

Biology

The colonies of dead man's fingers are nearly always either male or female, although a small number of

hermaphrodite In reproductive biology, a hermaphrodite () is an organism that has both kinds of reproductive organs and can produce both gametes associated with male and female sexes. Many taxonomic groups of animals (mostly invertebrates) do not have ...

colonies are found. Colony growth occurs mainly in the first half of the year with the polyps becoming inactive in late summer, and the base tissue turning reddish or brownish due to the growth of

alga Algae ( , ; : alga ) are any of a large and diverse group of photosynthetic, eukaryotic organisms. The name is an informal term for a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from u ...

e and

hydroids Hydroids are a life stage for most animals of the class Hydrozoa, small predators related to jellyfish. Some hydroids such as the freshwater ''Hydra'' are solitary, with the polyp attached directly to the substrate. When these produce buds, ...

on the surface. At this time the gonads are developing and spawning occurs in December and January. Populations have been found to synchronize their gametogenesis and spawning activities. artnoll, R.G. (1975). The annual cycle of ''Alcyonium digitatum''. Estuarine, Coastal and Shelf Science 3: 71-78. Fertilisation takes place externally and the embryos float for a few days before developing into free swimming larvae. Most of these soon settle on a suitable substrate and new polyps develop but a few may remain in the zooplankton for some time and disperse over a wide area. Colonies have been known to live for twenty years. The polyps feed at various times of the day with their tentacles extended. They are

suspension feeder Filter feeders are a sub-group of suspension feeding animals that feed by straining suspended matter and food particles from water, typically by passing the water over a specialized filtering structure. Some animals that use this method of feedin ...

s gathering

plankton Plankton are the diverse collection of organisms found in water (or air) that are unable to propel themselves against a current (or wind). The individual organisms constituting plankton are called plankters. In the ocean, they provide a cr ...

from the water with the help of cilia, and absorbing

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as we ...

at the same time.

References

External links

* * * {{Taxonbar, from=Q593303 Alcyoniidae Corals described in 1758 Taxa named by Carl Linnaeus