Sea pen

Sea pens are colonial marine cnidarians belonging to the order Pennatulacea. There are 14 families within the order; 35 extant genera, and it is estimated that of 450 described species, around 200 are valid.[1] Sea pens have a cosmopolitan distribution, being found in tropical and temperate waters worldwide, as well as from the intertidal to depths of more than 6100m.[1] Sea pens are grouped with the octocorals ("soft corals"), together with sea whips or gorgonians.

Although the group is named for its supposed resemblance to antique quill pens, only sea pen species belonging to the suborder Subselliflorae live up to the comparison. Those belonging to the much larger suborder Sessiliflorae lack feathery structures and grow in club-like or radiating forms. The latter suborder includes what are commonly known as sea pansies.

The earliest accepted fossils are known from the Cambrian-aged Burgess Shale (Thaumaptilon). Similar fossils from the Ediacaran (ala Charnia) may show the dawn of sea pens. Precisely what these early fossils are, however, is not decided.

Sea pen
Temporal range: Cambrian–Recent
Haeckel Pennatulida
"Pennatulida" from Ernst Haeckel's Kunstformen der Natur, 1904
Scientific classification
Kingdom: Animalia
Phylum: Cnidaria
Class: Anthozoa
Subclass: Octocorallia
Order: Pennatulacea
Verrill, 1865

See text


The order Pennatulacea consists of the following families:[2]

Pennatula phosphorea

Pennatula phosphorea (Pennatulidae)

Veretillum sp. (Sea pen) at night

Veretillum sp. (Veretillidae)


Sea pen uprooted
Uprooted sea pen with the bulbous peduncle in view

As octocorals, sea pens are colonial animals with multiple polyps (which look somewhat like miniature sea anemones), each with eight tentacles. Unlike other octocorals, however, a sea pen's polyps are specialized to specific functions: a single polyp develops into a rigid, erect stalk (the rachis) and loses its tentacles, forming a bulbous "root" or peduncle at its base.[3] The other polyps branch out from this central stalk, forming water intake structures (siphonozooids), feeding structures (autozooids) with nematocysts, and reproductive structures. The entire colony is fortified by calcium carbonate in the form of spicules and a central axial rod.

Using their root-like peduncles to anchor themselves in sandy or muddy substrate, the exposed portion of sea pens may rise up to 2 metres (6.6 ft) in some species, such as the tall sea pen (Funiculina quadrangularis). Sea pens are sometimes brightly coloured; the orange sea pen (Ptilosarcus gurneyi) is a notable example. Rarely found above depths of 10 metres (33 ft), sea pens prefer deeper waters where turbulence is less likely to uproot them. Some species may inhabit depths of 2,000 metres (6,600 ft) or more.

While generally sessile animals, sea pens are able to relocate and re-anchor themselves if need be.[3] They position themselves favourably in the path of currents, ensuring a steady flow of plankton, the sea pens' chief source of food. Their primary predators are nudibranchs and sea stars, some of which feed exclusively on sea pens. When touched, some sea pens emit a bright greenish light; this is known as bioluminescence. They may also force water out of their bodies for defence, rapidly deflating and retreating into their peduncle.

Like other anthozoans, sea pens reproduce by co-ordinating a release of sperm and eggs into the water column; this may occur seasonally or throughout the year. Fertilized eggs develop into larvae called planulae which drift freely for about a week before settling on the substrate. Mature sea pens provide shelter for other animals, such as juvenile fish. Analysis of rachis growth rings indicates sea pens may live for 100 years or more, if the rings are indeed annual in nature.

Some sea pens exhibit glide reflection symmetry,[4] rare among non-extinct animals.

Aquarium trade

Sea pens are sometimes sold in the aquarium trade. However, they are generally hard to care for because they need a very deep substrate and have special food requirements.


  1. ^ a b Williams, Gary C. (2011-07-29). Thrush, Simon (ed.). "The Global Diversity of Sea Pens (Cnidaria: Octocorallia: Pennatulacea)" (PDF). PLoS ONE. 6 (7): e22747. Bibcode:2011PLoSO...622747W. doi:10.1371/journal.pone.0022747. PMC 3146507. PMID 21829500. Archived (PDF) from the original on 2019-10-09.
  2. ^ "Pennatulacea". World Register of Marine Species. Retrieved 2018-04-03.
  3. ^ a b Barnes, Robert D. (1982). Invertebrate Zoology. Philadelphia, PA: Holt-Saunders International. pp. 168–169. ISBN 0-03-056747-5.
  4. ^ Zubi, Teresa (2016-01-02). "Octocorals (Stoloniferans, soft corals, sea fans, gorgonians, sea pens) - Starfish Photos - Achtstrahlige Korallen (Röhrenkorallen, Weichkorallen, Hornkoralllen, Seefedern, Fächerkorallen)". Retrieved 2016-09-08.

External links


Actinoptilum is a genus of sea pen in the family Echinoptilidae. It is monotypic with a single species, Actinoptilum molle, commonly known as the radial sea pen or purple sea pen, which is found off the coasts of South Africa.


Alcyonacea, or soft corals, are an order of corals that do not produce calcium carbonate skeletons. Formerly known as gorgonians, they are sessile colonial cnidarians found throughout the oceans of the world, especially in the tropics and subtropics. Common names for subset of this order are sea fans and sea whips and are similar to the sea pen, a soft coral. Individual tiny polyps form colonies that are normally erect, flattened, branching, and reminiscent of a fan. Others may be whiplike, bushy, or even encrusting. A colony can be several feet high and across, but only a few inches thick. They may be brightly coloured, often purple, red, or yellow. Photosynthetic gorgonians can be successfully kept in captive aquaria.

About 500 different species of gorgonians are found in the oceans of the world, but they are particularly abundant in the shallow waters of the Western Atlantic, including Florida, Bermuda, and the West Indies.

Atlantis Marine Park

Atlantis Marine Park is an abandoned theme park built in 1981 in Two Rocks, a small fishing community 60 kilometres (37 mi) north of Perth, the capital of Western Australia. The park was a major feature of Alan Bond's Yanchep Sun City plan. It closed in August 1990 due to financial difficulty.


Benthos is the community of organisms that live on, in, or near the seabed, river, lake, or stream bottom, also known as the benthic zone. This community lives in or near marine or freshwater sedimentary environments, from tidal pools along the foreshore, out to the continental shelf, and then down to the abyssal depths.

Many organisms adapted to deep-water pressure cannot survive in the upperparts of the water column. The pressure difference can be very significant (approximately one atmosphere for each 10 metres of water depth).Because light is absorbed before it can reach deep ocean-water, the energy source for deep benthic ecosystems is often organic matter from higher up in the water column that drifts down to the depths. This dead and decaying matter sustains the benthic food chain; most organisms in the benthic zone are scavengers or detritivores.

The term benthos, coined by Haeckel in 1891, comes from the Greek noun βένθος "depth of the sea". Benthos is used in freshwater biology to refer to organisms at the bottom of freshwater bodies of water, such as lakes, rivers, and streams. There is also a redundant synonym, benthon.


Charnia is a genus of frond-like Ediacaran lifeforms with segmented, leaf-like ridges branching alternately to the right and left from a zig-zag medial suture (thus exhibiting glide reflection, or opposite isometry). The genus Charnia was named after Charnwood Forest in Leicestershire, England, where the first fossilised specimen was found. Charnia is significant because it was the first Precambrian fossil to be recognized as such.

The living organism was a type of life form that grew on the sea floor and is believed to have fed on nutrients in the water. Despite Charnia's fern-like appearance, it is not a photosynthetic plant or alga because the nature of the fossilbeds where specimens have been found implies that it originally lived in deep water, well below the photic zone where photosynthesis can occur.

Dolphin Reef

Dolphin Reef is a horseshoe-shaped sea-pen where bottlenose dolphins in the Gulf of Eilat in the northern-eastern Red Sea near the city of Eilat in southern Israel swim in and out of. It is a major tourist attraction in this area.

Eilean Choraidh

Eilean Choraidh, also known as Horse Island is an island in Loch Eriboll in Sutherland on the north coast of Scotland. It is about 26 hectares (64 acres) in extent and the highest point is 26 metres (85 ft) above sea level.

During the 19th century the Reay estate quarried lime from Eilean Choraidh, treated it in kilns on the nearby peninsula of Ard Neakie, and exported it by ship.The census of 1931 records a single male inhabitant, and there has been no indication of any permanent residents since then. This may be partly because Eilean Choraidh was used as a representation of the German battleship Tirpitz for target practice by Mosquito bombers of the Royal Air Force during World War II. The Ordnance Survey indicate the presence of two ruined buildings, one in the centre of the island north of a long wall that runs east to west and another at the north end. Today, the island is used for grazing sheep.A variety of wild mammals are present including otters, grey seals and cetaceans. Beds of maerl, a corraline algae that has been identified as a priority habitat in the UK

Biodiversity Action Plan, has been recorded in the channels on either side of Eilean Choraidh. The sea pen,

Virgularia mirabilis is also present in the inner loch.


Feathery sea pen

The feathery sea pen (Virgularia schultzei) is a species of sea pen in the family Virgulariidae.

Funiculina quadrangularis

Funiculina quadrangularis is an uncommon species of sea pen within the Family Funiculinidae. It forms habitat for several key crustation species.

Morgan (killer whale)

Morgan is a female orca who was rescued in the Wadden Sea, off the northwestern coast of the Netherlands in June 2010. She was found in an unhealthy condition, severely underweight and malnourished. She lived several months at the Dolfinarium Harderwijk in the Netherlands. After it became clear that the basin at Dolfinarium was too small, multiple options were considered, including releasing Morgan and transferring her to another facility. Over a year later, after litigation and debate between scientists, a Dutch court ruled that she was to be moved. Morgan was transported to the Loro Parque in Spain in November 2011.


Pennatulidae is a family of sea pens, a member of the subclass Octocorallia in the phylum Cnidaria.

Pierre's armina

Pierre's armina, scientific name Armina sp. (as designated by Zsilavecz, 2007), is a species of sea slug, a nudibranch. It is a marine gastropod mollusc in the family Arminidae. This species was undescribed by science as of November 2009.


Plumage (Latin: plūma "feather") is a layer of feathers that cover a bird and the pattern, colour, and arrangement of those feathers. The pattern and colours of plumage differ between species and subspecies and may vary with age classes. Within species, there can be different colour morphs. The placement of feathers on a bird is not haphazard, but rather emerge in organized, overlapping rows and groups, and these feather tracts are known by standardized names.Most birds moult twice a year, resulting in a breeding or nuptial plumage and a basic plumage. Many ducks and some other species such as the red junglefowl have males wearing a bright nuptial plumage while breeding and a drab eclipse plumage for some months afterward. The painted bunting's juveniles have two inserted moults in their first autumn, each yielding plumage like an adult female. The first starts a few days after fledging replacing the juvenile plumage with an auxiliary formative plumage; the second a month or so later giving the formative plumage.Abnormal plumages include a variety of conditions. Albinism, total loss of colour, is rare, but partial loss of colours is more common. Some species are colour polymorphic, having two or more colour variants. A few species have special types of polymorphism, as in the male ruff which has an assortment of different colours around the head and neck in the breeding season only.

Hen feathering is an inherited plumage character in domestic fowl controlled by a single gene. Plumology (or plumage science) is the name for the science that is associated with the study of feathers.

Ptilosarcus gurneyi

Ptilosarcus gurneyi, the orange sea pen or fleshy sea pen, is a species of sea pen in the family Pennatulidae. It is native to the northeastern Pacific Ocean where it lives in deep water anchored by its base in sand or mud. It has received its common name because of its resemblance to a quill in a bottle of ink.


Renilla is a genus of sea pen. It is the only genus within the monotypic family Renillidae.

Renilla koellikeri

Renilla koellikeri (also spelled R. kollikeri or R. köllikeri) is a species of sea pen that has been reported from the southern coast of California, including Santa Barbara, California.


Virgularia is a genus of sea pen in the family Virgulariidae.

William Stafford (poet)

William Edgar Stafford (January 17, 1914 – August 28, 1993) was an American poet and pacifist. He was the father of poet and essayist Kim Stafford. He was appointed the twentieth Consultant in Poetry to the Library of Congress in 1970.

Stony corals
Soft corals
Coral reefs
Coral regions
Coral diseases


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