| Notocrinus virilis | |
|---|---|
 | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Echinodermata |
| Class: | Crinoidea |
| Order: | Comatulida |
| Family: | Notocrinidae |
| Genus: | Notocrinus |
| Species: | N. virilis |
| Binomial name | |
| Notocrinus virilis | |
Notocrinus virilis is a marine invertebrate, a species of crinoid or feather star in the family Notocrinidae. It is found in deep water in the Southern Ocean around the coasts of Antarctica and adjacent islands. [2] A sea snail sometimes parasitizes it.
Notocrinus virilis is a robust, stalkless crinoid with ten arms (five arms, each subdivided into two) up to 200 mm (8 in) long. There are five deep radial pits on the centro-dorsal axis of the disc, forming a "radial star". There are fewer than fifty cirri at the base of the calyx. The pinnules that extend from either side of the arms are relatively short and are circular in cross section. The gonads are on the lower pinnules and there are brood pouches between these pinnules and the arms. This crinoid is dark red in colour, a colour that is already becoming apparent in the late stage, stalked larvae. [2]
Endemic to the Southern Ocean waters around Antarctica, N. virilis probably has a circumpolar distribution. It is known from the Antarctic Peninsula, the South Orkney Islands, the Enderby Land, the Adélie Land, the Balleny Islands and the Ross Sea. Its depth range is between 80 and 1,120 m (260 and 3,670 ft). [3]
This species can crawl around using its cirri and can also use them to climb to an elevated position in which to feed. [3] Like all crinoids, it is a filter feeder, spreading its arms and pinnules widely to catch plankton and small particles of detritus from the water flowing past. The sexes are separate, and females brood their young in their brood pouches; the larvae may reach 1.8 mm (0.07 in) in length before being expelled from the pouch and falling to the sea bed, to which they will anchor themselves. [4]
In early deep sea research, organisms were dredged up from the sea bed but during the trawl, any link between one species and another was often lost. More recently, it has been discovered that N. virilis often has a gastropod mollusc, Bathycrinicola tumidula , attached to it, the first time a snail from this family has been associated with a crinoid. Research in 2007 by Schiaparelli showed that B. tumidula is parasitic on N. virilis, and no other Antarctic crinoids have been found to act as hosts to the mollusc. Some of the parasitic snails were found to have inserted their proboscises between ossicles near the base of the crown while others were attached between calcareous plates on the arms. [3]
An echinoderm is any member of the phylum Echinodermata. The adults are recognisable by their radial symmetry, and include starfish, brittle stars, sea urchins, sand dollars, and sea cucumbers, as well as the sea lilies or "stone lilies". Adult echinoderms are found on the sea bed at every ocean depth, from the intertidal zone to the abyssal zone. The phylum contains about 7,000 living species, making it the second-largest grouping of deuterostomes, after the chordates. Echinoderms are the largest entirely marine phylum. The first definitive echinoderms appeared near the start of the Cambrian.
Crinoids are marine animals that make up the class Crinoidea. Crinoids that are attached to the sea bottom by a stalk in their juvenile form are commonly called sea lilies, while the unstalked forms, called feather stars or comatulids, are members of the largest crinoid order, Comatulida. Crinoids are echinoderms in the phylum Echinodermata, which also includes the starfish, brittle stars, sea urchins and sea cucumbers. They live in both shallow water and in depths as great as 9,000 meters (30,000 ft).
Thorson's rule is an ecogeographical rule which states that benthic marine invertebrates at low latitudes tend to produce large numbers of eggs developing to pelagic and widely dispersing larvae, whereas at high latitudes such organisms tend to produce fewer and larger lecithotrophic (yolk-feeding) eggs and larger offspring, often by viviparity or ovoviviparity, which are often brooded.
Antedon bifida is a species of crinoid in the family Antedonidae commonly known as the rosy feather star. It is found in north west Europe.
Antedon petasus is a marine invertebrate, a species of crinoid or feather star in the family Antedonidae. It is found around the coasts of north west Europe.
Comatulida is an order of crinoids. Members of this order are known as feather stars and mostly do not have a stalk as adults. The oral surface with the mouth is facing upwards and is surrounded by five, often divided rays with feathery pinnules. Comatulids live on the seabed and on reefs in tropical and temperate waters.
Davidaster discoideus, the beaded crinoid, is a species of feather star in the family Comatulidae. It was previously known as Nemaster discoidea but the World Register of Marine Species has determined that the valid name is Davidaster discoideus. It is found on reefs in the Caribbean Sea and northern coast of South America.
Comaster schlegelii, the variable bushy feather star, is a crinoid in the family Comatulidae. It was previously classified as Comanthina schlegeli but further research showed that it was better placed in the genus Comaster. It is found on shallow water reefs in the western Pacific Ocean.
Metacrinus rotundus, the Japanese sea lily, is a marine invertebrate, a species of stalked crinoid in the family Isselicrinidae. It is a species found off the west coast of Japan, and is living near the edge of the continental shelf, around 100–150m deep. This is the shallowest species among the extant stalked crinoids.
Oxycomanthus bennetti, the Bennett's feather star, is a species of crinoid belonging to the family Comatulidae. It is found in shallow water in the Indo-Pacific between northern Australia and southeast Asia.
Bathycrinicola tumidula is a species of sea snail, a marine gastropod mollusc in the family Eulimidae.
Antedon mediterranea is a species of stalkless crinoid in the family Antedonidae, commonly known as the Mediterranean feather star. It is found on the seabed at moderate depths in the Mediterranean Sea. It is a filter feeder and captures plankton with its long feathery arms.
Cenocrinus is a monotypic genus of stalked crinoids in the family Isselicrinidae. The great West Indian sea lily is the only species in the genus and is found in deep waters in the Caribbean Sea and Gulf of Mexico.
Ptilometra australis, the passion flower feather star, is a species of crinoid. It is native to the coasts of southeastern Australia where it is found on reefs, in estuaries and bays at depths down to about 110 metres (360 ft).
Leptometra celtica is a marine invertebrate and species of crinoid or feather star of the Leptometra genus in the family Antedonidae. It is found in the Atlantic Ocean around the coasts of north west Europe. The presence of L. celtica and L. phalangium is considered to be a good indication of nearby shelf breaks, general bottom currents, and areas of high gross productivity as they are suspension-feeders, hence their proliferation in productive environments.
Promachocrinus kerguelensis is a species of free-swimming, stemless crinoids. It was the only member of its genus until several species were discovered in 2023. P. keruguelensis a coldwater crinoid which is found in the seas around Antarctica and surrounding island groups, including under the sea ice.
Aporometra wilsoni is a marine invertebrate, a species of crinoid or feather star in the family Aporometridae. It is found in shallow water around the coasts of southern Australia.
Notocrinidae is a monotypic family of crinoids, the only genus being Notocrinus, which contains two species, both endemic to the seas around Antarctica.
Aporometra paedophora is a marine invertebrate, a species of crinoid or feather star in the family Aporometridae. It was first found at a depth of 22 fathoms off the Manning River on the New South Wales coast. Other specimens were found off the coast of Bunbury, Western Australia at depths between 9 and 15 m. Based on morphological evidence of four specimens of A. paedophora, Helgen & Rouse believe that this may not be a separate species from Aporometra wilsoni.
Cenometra bella is a species of crinoids belonging to the genus Cenometra. They can have up to 30 arms and can be of variable colours but are often characterised by a marked contrast between the extending free-arms and the feathery pinnules. This species clings to its support and moves around by its feet-like cirri.
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