Primnoa

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Primnoa
Temporal range: Early Paleocene–Recent
Rockfish red tree coral.png
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Cnidaria
Class: Octocorallia
Order: Alcyonacea
Family: Primnoidae
Genus: Primnoa
Lamouroux, 1812
Species

Primnoa(Lamororux, 1812) also known as red tree coral, is a genus of soft corals and the type genus of the family Primnoidae (Milne Edwards, 1857). [1] They are sessile, benthic cnidarians that can be found in the North Pacific, North Atlantic, and Subantarctic South Pacific, [2] and its members often play a vital ecological role as keystone species [3] within their environment as a habitat and refuge for the megafauna that also inhabit those regions. [4] This, in combination with their slow growth, makes the increasing disturbance to their habitats caused by fishing activities particularly impactful and difficult to recover from. [5]

Contents

Etymology

The name Primnoa derives from the Greek word Πρυμνὼ (Prymno), [6] the name of an Oceanid. The name itself is derived from πρυμνός (prymnos), meaning “last”, “lowest”, and by extension, “deepest”. [7]

Taxonomy

The genus Primnoa was first described by Jean Vincent Félix Lamouroux in 1812. [5] In the 19th and 20th century, several more species were proposed as members of Primnoa, but most were originally described as members of other genera within Primnoidae. Currently there are only five valid species and one variety that are recognized members of the genus. [1] [8] Their details are tabulated below:

SpeciesDetailsImage
P. bisquama (Taylor & Rogers, 2017)Found in the Southwest Indian Ocean. Light pink in color. Its most distinguishing feature is its low-rise operculum, fewer number of large body-wall scales, and infrequent, relatively smaller polyps [9]
P. bisquama (on the left) Primnoa bisquama.png
P. bisquama (on the left)
P. notialis (Cairns & Bayer, 2005)Found in the Subantarctic South Pacific Ocean At depths of 549-915m. Its most distinguishing feature is the variation in the number of body-wall scales, which are occasionally in excess. [8]
P. notialis Primnoa notialis.jpg
P. notialis
P. pacifica (Kinoshita, 1907)P. pacifica typical is found in the Sea of Japan, the Sea of Okhotsk, the Aleutian Islands, the Bering Sea, and the northeast Pacific coast from Alaska to La Jolla, California, at 9-800 m. It is pink in color and its most distinguishing features are its massive basal body-wall scales, as well as the presence of a margina spine similar to those found in Narella. [8] [2]
P. pacifica typical Primnoa pacifica with crab.png
P. pacifica typical
P. pacifica var willeyi is found in the Aleutian Islands to British Columbia at depths of 183-755 m. It differs from the typical form in that is orange in color and has more slender polyps. [8] [2]
P. pacifica var willeyi Primnoa pacifica var. willeyi.png
P. pacifica var willeyi
P. resedaeformis (Gunnerus, 1763)Found in the North Atlantic from Virginia Beach to Greenland at 91-548 m. Found in the Eastern Atlantic from Greenland to Scotland at 95-1,020 m. It is bright pink in color. Its most distinguishing feature are its rectangular basal body-wall scales. [8]
P. resedaeformis Primnoa resedaeformis.jpg
P. resedaeformis
P. wingi (Cairns & Bayer, 2005)Found in the Aleutian Islands and the Bering Sea at 110-914 m, and is pink in color. Its most distinguishing feature are its inconspicuous body-wall scales, as well as its uniquely shaped opercular scales. [8] [2]
P. wingi Primnoa wingi specimen.jpg
P. wingi

Anatomy and physiology

Close up view of P. pacifica polyps Close up of Primnoa pacifica.png
Close up view of P. pacifica polyps

Primnoa colonies are typically bushy in shape, heavily branched with no immediately visible main stem, though they do possess one. They also dichotomously branch, meaning that they separate into two equally sized branches at every branching point. [10] They have large polyps that are non-retractile which are protected by a polyp composed of six overlapping rows of calcitic scales, with adaxial (stem-facing) scales tending to be smaller than their outward facing counterparts, or absent altogether. [2] Polyps are individually distinct, usually appressed and downward facing, but otherwise randomly arranged and close together. [9] Due to their predatory nature, most have small, thorny tentacles, and a well-developed operculum at the tip of the polyp. [11] Primnoa are monomorphic, thus only having one type of polyp. Their internal anatomy is consistent with that of other gorgonian corals. [12] The physical differences between species in this genus primarily derive from variances in body scale shape and number. Species in these genus have colors that range from pink to reddish-orange. [8]

They are also ahermatypic, which means they aren’t reef building corals, but they still form large structures and are found in abundance in clusters of colonies. [13] Like many other octocorals, rather than using calcium carbonate in the form of aragonite (which is used by Scleractinian corals), Primnoa use a more stable form called calcite, which is less soluble in seawater. They anchor themselves to hard substrates using calcareous discoid holdfasts, which are then further supported by growing layers of calcite at the base of the colony. [5]

Behaviour and life history

Reproduction

Not much is known about the reproduction of Primnoa species. So far, it has been established that Primnoa are gonochoristic corals, meaning that each colony is either male or female. [12] Reproduction occurs via broadcast spawning, which results in the organisms externally fertilizing their eggs. Unlike most corals which use this method, there is no evidence of  reproductive periodicity or synchronized mass spawning events. [14]

Feeding

Like many other deep-water corals, Primnoa are azooxanthellate, meaning that they do not have symbiotic relationships with Symbiodinium. Instead, they received nutrition via filter-feeding and obtain food directly from the water column. [15] Studies suggest that Primnoa are primarily carnivorous, feeding on sinking particulate organic matter and zooplankton. The possibility of them eating resuspended meiofauna has also been proposed, given their downward facing polyps. [13]

Ecology

Many species of Primnoa are considered ecologically important, acting as keystone species, foundation species, and ecological engineers because their complex branching and large size allow them to serve as a habitat by providing shelter and substrate for many animals. [16] [5]

Some species of suspension feeders use the branches of Primnoa to obtain nutrients, by elevating their position in the water and collecting floating particles that circulate the water column,. These species include various crinoids, basket stars, anemones, and sponges. Suspension feeders have been reported in association with Primnoa at depths greater than 300 m. [4]

Species also seek shelter and protection using the branches of Primnoa to hide them from predators. These species include types of crabs, shrimps, and rockfish. Shrimp are observed to be hiding among the polyps of the corals, while crabs were found beneath them. Rockfish were found both beneath and among the polyps. In some circumstances, species were found to be using the protection of the coral polyps for reproductive purposes, as they were well hidden from predators among the coral’s branches. [4]

Predation

Predators of the Primnoa include sea stars, nudibranchs, and snails, though sea stars are their primary predators. One study found that sea stars were responsible for 45-34% of the consumption of the soft coral polyps. [4]

Distribution and habitat

Primnoa require hard substrate they can firmly attach to, such as rocky outcrops or boulders. These hard substrates allow them to live in areas with strong currents, a preference which increases their odds of capturing food due to the higher velocity and volume of water passing through their branches. [5] [12]

Despite being characterized as deep water corals, Primnoa can also be found in shallow water habitats. The total bathymetric range occupied by the genus is between 6-1,020 m. [2] However, Primnoa being present in these shallow regions is due to a phenomenon known as deep-sea emergence, which is defined as “a phenomenon whereby organisms that typically dwell in the deep sea are able to exist in shallow-water areas because of unusual oceanographic conditions there.” [17] In this case, retreating glaciers have resulted in exposed bedrock and very cool temperatures that are similar to the deep-water temperatures preferred by Primnoa, as well as other factors that help mimic their natural environment. [12]  Additionally, one study observed how some coral grew in atypical forms due to poor health, causing them to become ecomorphs due to the stress of living in unfavorable conditions such as turbidity and periods of increased water temperature higher than they could tolerate. [17]

The Aleutian Islands

The Aleutian Islands are an island chain off the coast of Alaska, in the North Pacific. They range approximately 6,821 square miles, and are made up of around 300 islands, including 14 larger volcanic islands. The waters are cold and nutrient rich due to the active margins they inhabit, and experience large amounts of upwelling from the seafloor.

The benthic environments in which Primnoa are found provide the capacity for unique and highly diverse sponges and soft corals. These organisms in turn provide the basis for a habitat to many vertebrate species such as fish. This region is home to the most productive fisheries of the Northern Pacific due to the benthic abundance and its capacity to support vertebrate species. In general, corals are most abundant at depths between 100 and 200 m, but can be found anywhere from 27 to 363 m down. [18]

19 species of corals known in the Aleutian Islands belong to the Primnoidae family, and 25 of the 69 documented species of corals in the Aleutian Isles, including P. wingi are endemic species. [2] [19] Meaning they are restricted to the geographical range that spans the Aleutian Islands; however this diversity begins to increase west of 169°W. [19] It is believed by some scientists that the Aleutian Islands serve as the evolutionary cradle for some taxa of cold water soft corals, due to the sheer diversity and abundance of the organisms that the waters display.

Threats and conservation measures

Fishing methods

The largest risk for this family of corals comes from fisheries and net trawling, which uproots the corals and destroys them. Sometimes, the corals are worn by natives as jewelry, as they are bycatch of the fishing hawks and do not have other nutritive or practical uses. Nearly 39% of the seafloor of the Aleutian Islands shows disturbance due to bottom-contact fishing tools and gear such as nets. [18] Because of their vital interactions with megafauna in these ecosystems, fisheries must integrate coral conservation into their practices, or otherwise risk disturbance to their entire industry.

Related Research Articles

<span class="mw-page-title-main">Coral</span> Marine invertebrates of the class Anthozoa

Corals are colonial marine invertebrates within the class Anthozoa of the phylum Cnidaria. They typically form compact colonies of many identical individual polyps. Coral species include the important reef builders that inhabit tropical oceans and secrete calcium carbonate to form a hard skeleton.

<span class="mw-page-title-main">Bering Sea</span> Sea of the northern Pacific Ocean off the coast of Alaska and Russia

The Bering Sea is a marginal sea of the Northern Pacific Ocean. It forms, along with the Bering Strait, the divide between the two largest landmasses on Earth: Eurasia and the Americas. It comprises a deep water basin, which then rises through a narrow slope into the shallower water above the continental shelves. The Bering Sea is named after Vitus Bering, a Danish navigator in Russian service, who, in 1728, was the first European to systematically explore it, sailing from the Pacific Ocean northward to the Arctic Ocean.

<span class="mw-page-title-main">Anthozoa</span> Class of cnidarians without a medusa stage

Anthozoa is a class of marine invertebrates which includes the sea anemones, stony corals and soft corals. Adult anthozoans are almost all attached to the seabed, while their larvae can disperse as part of the plankton. The basic unit of the adult is the polyp; this consists of a cylindrical column topped by a disc with a central mouth surrounded by tentacles. Sea anemones are mostly solitary, but the majority of corals are colonial, being formed by the budding of new polyps from an original, founding individual. Colonies are strengthened by calcium carbonate and other materials and take various massive, plate-like, bushy or leafy forms.

<span class="mw-page-title-main">Sea pen</span> Order of colonial marine cnidarians

Sea pens are colonial marine cnidarians belonging to the order Pennatulacea. The order Pennatulacea, commonly known as sea pens, are colony-forming benthos belonging within subclass Octocorallia. Sea pens are found worldwide from shallow to deep waters, and they are important components in sandy and muddy environments. Thus far, there has been only one molecular study focusing on the phylogenetic relationships within the order Pennatulacea, which mainly treated deep-sea species, and thus information on shallow water species is still lacking. There are 14 families within the order and 35 extant genera; it is estimated that of 450 described species, around 200 are valid. 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 6100 m. Sea pens are grouped with the octocorals, together with sea whips (gorgonians).

<span class="mw-page-title-main">Gulf of Alaska</span> Arm of the Pacific Ocean

The Gulf of Alaska is an arm of the Pacific Ocean defined by the curve of the southern coast of Alaska, stretching from the Alaska Peninsula and Kodiak Island in the west to the Alexander Archipelago in the east, where Glacier Bay and the Inside Passage are found.

<span class="mw-page-title-main">Black coral</span> Order of soft deep-water corals with chitin skeletons

Antipatharians, also known as black corals or thorn corals, are an order of soft deep-water corals. These corals can be recognized by their jet-black or dark brown chitin skeletons, which are surrounded by their colored polyps. Antipatharians are a cosmopolitan order, existing in nearly every oceanic location and depth, with the sole exception of brackish waters. However, they are most frequently found on continental slopes under 50 m (164 ft) deep. A black coral reproduces both sexually and asexually throughout its lifetime. Many black corals provide housing, shelter, food, and protection for other animals.

<i>Lophelia</i> Species of cnidarian

Lophelia pertusa, the only species in the genus Lophelia, is a cold-water coral that grows in the deep waters throughout the North Atlantic ocean, as well as parts of the Caribbean Sea and Alboran Sea. Although L. pertusa reefs are home to a diverse community, the species is extremely slow growing and may be harmed by destructive fishing practices, or oil exploration and extraction.

<span class="mw-page-title-main">Staghorn coral</span>

The Staghorn coral is a branching, stony coral, within the Order Scleractinia. It is characterized by thick, upright branches which can grow in excess of 2 meters in height and resemble the antlers of a stag, hence the name, Staghorn. It grows within various areas of a reef but is most commonly found within shallow fore and back reefs, as well as patch reefs, where water depths rarely exceed 20 meters. Staghorn corals can exhibit very fast growth, adding up to 5 cm in new skeleton for every 1 cm of existing skeleton each year, making them one of the fastest growing fringe coral species in the Western Atlantic. Due to this fast growth, Acropora cervicornis, serve as one of the most important reef building corals, functioning as marine nurseries for juvenile fish, buffer zones for erosion and storms, and center points of biodiversity in the Western Atlantic.

<span class="mw-page-title-main">Alcyonacea</span> Order of octocorals that do not produce massive calcium carbonate skeletons

Alcyonacea are an order of sessile colonial cnidarians that are found throughout the oceans of the world, especially in the deep sea, polar waters, tropics and subtropics. Whilst not in a strict taxonomic sense, Alcyonacea are commonly known as soft corals. The term "soft coral" generally applies to organisms in the two orders Pennatulacea and Alcyonacea with their polyps embedded within a fleshy mass of coenenchymal tissue. Consequently, the term "gorgonian coral" is commonly handed to multiple species in the order Alcyonacea that produce a mineralized skeletal axis composed of calcite and the proteinaceous material gorgonin only and corresponds to only one of several families within the formally accepted taxon Gorgoniidae (Scleractinia). These can be found in order Malacalcyonacea (taxonomic synonyms of include : Alcyoniina, Holaxonia, Protoalcyonaria, Scleraxonia, and Stolonifera. They are sessile colonial cnidarians that are found throughout the oceans of the world, especially in the deep sea, polar waters, tropics and subtropics. Common names for subsets of this order are sea fans and sea whips; others are similar to the sea pens of related order Pennatulacea. 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.

<span class="mw-page-title-main">Tracy Arm</span> Fjord in Alaska, U.S.

Tracy Arm is a fjord in the U.S. state of Alaska near Juneau. It is named after the Secretary of the Navy Benjamin Franklin Tracy. It is located about 45 miles (72 km) south of Juneau and 70 miles (110 km) north of Petersburg, Alaska, off of Holkham Bay and adjacent to Stephens Passage within the Tongass National Forest. Tracy Arm is the heart of the Tracy Arm-Fords Terror Wilderness, designated by the United States Congress in 1990

<span class="mw-page-title-main">Octocorallia</span> Class of Anthozoa with 8-fold symmetry

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<span class="mw-page-title-main">Ivory bush coral</span> Species of cnidarian

Oculina varicosa, or the ivory bush coral, is a scleractinian deep-water coral primarily found at depths of 70-100m, and ranges from Bermuda and Cape Hatteras to the Gulf of Mexico and the Caribbean. Oculina varicosa flourishes at the Oculina Bank off the east coast of Florida, where coral thickets house a variety of marine organisms. The U.S. National Marine Fisheries Service considers Oculina a genus of concern, due to the threat of rapid ocean warming. Species of concern are those species about which the U.S. Government's National Oceanic and Atmospheric Administration (NOAA), National Marine Fisheries Service, has some concerns regarding status and threats, but for which insufficient information is available to indicate a need to list the species under the U.S. Endangered Species Act (ESA). While Oculina is considered a more robust genus in comparison to tropical corals, rising ocean temperatures continue to threaten coral health across the planet.

<span class="mw-page-title-main">Deep-water coral</span> Marine invertebrates

The habitat of deep-water corals, also known as cold-water corals, extends to deeper, darker parts of the oceans than tropical corals, ranging from near the surface to the abyss, beyond 2,000 metres (6,600 ft) where water temperatures may be as cold as 4 °C (39 °F). Deep-water corals belong to the Phylum Cnidaria and are most often stony corals, but also include black and thorny corals and soft corals including the Gorgonians. Like tropical corals, they provide habitat to other species, but deep-water corals do not require zooxanthellae to survive.

<span class="mw-page-title-main">Coralliidae</span> Family of corals

Coralliidae, also known as precious corals, is a taxonomic family of soft corals belonging to the suborder Scleraxonia of the phylum Cnidaria. These sessile corals are one of the most dominant members of hard-bottomed benthic environments such as seamounts, canyons and continental shelves. From this coral family results 69 descendants in which each species plays a key role in forming habitats for a variety of marine species.

<i>Primnoa pacifica</i> Species of coral

Primnoa pacifica or red tree coral is a species of soft coral in the family Primnoidae. It is a deep water coral found in the North Pacific Ocean, and plays an integral role in supporting benthic ecosystems. Red tree corals grow axially and radially, producing structures of calcite and gorgonian skeletons that form dense thickets. Like other species of coral, red tree coral is made of a soluble form of calcium carbonate, which forms the reef structure, as well as provides food, shelter, and nutrients for surrounding organisms. Amongst the organisms red tree corals provide a home for, many are commercially important fish and crustaceans. These areas of marine habitat are listed as Habitat Areas of Particular Concern. However, anthropogenic impacts such as bottom trawling pose large-scale threats to these habitats. There are also concerns about the effects of ocean acidification on red tree coral, since it shares many of the same properties as other corals that are suffering from bleaching.

<i>Paragorgia arborea</i> Species of coral

Paragorgia arborea is a species of coral in the family Paragorgiidae, commonly known as the bubblegum coral because of its bulbous branch tips. It mainly grows in depths between 200 and 1,300 metres at temperatures between 3 and 8 °C. It is found widespread in the Northern Atlantic Ocean and Northern Pacific Ocean on seamounts and knolls, and was first described by the Swedish naturalist Carl Linnaeus in 1758. P. arborea is a foundation species, providing a habitat for other species in deep sea coral ecosystems.

<i>Seriatopora hystrix</i> Species of coral

Seriatopora hystrix is a species of colonial stony coral in the family Pocilloporidae. It forms a branching clump and is commonly known as thin birdsnest coral. It grows in shallow water on fore-reef slopes or in sheltered lagoons, the type locality being the Red Sea. It is native to East Africa, the Red Sea and the western Indo-Pacific region. It is a common species and the International Union for Conservation of Nature has assessed its conservation status as being of "least concern".

<i>Callogorgia</i> Genus of corals

Callogorgia is a genus of deep sea corals that are ideally suited to be habitats for different organisms. They reproduce both sexually and asexually, clinging to the hard substrate of the ocean during their maturation process. Callogorgia are found at depths ranging from 750-8200 feet in the Gulf of Mexico, Pacific Ocean and the Caribbean Sea. An array of organisms have relationships with Callogorgia, including brittle stars, cat sharks, and copepods. The nature of these relationships are often commensal, with Callogorgia providing a habitat for the organisms.

Callogorgia elegans is a species of soft corals in the family Primnoidae. It is found in the north-western Pacific Ocean. Like other coral species, C. elegans is bottom-dwelling and sessile, or immobile.

<i>Narella</i> Genus of corals

Narella is a genus of deep-sea soft corals in the family Primnoidae (Milne Edwards, 1857). They are sessile, bottom-dwelling organisms that can be found in all ocean basins, having cosmopolitan distribution. They have a branching appearance.

References

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