Freyellidae | |
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Freyastera sp. south from Porto Rico (4500m deep) | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Echinodermata |
Class: | Asteroidea |
Order: | Brisingida |
Family: | Freyellidae Downey, 1986 [1] [2] |
Genera | |
See text |
The Freyellidae are a family of deep-sea-dwelling starfish. It is one of two families in the order Brisingida. [3] The majority of species in this family are found in Antarctic waters and near Australia. Other species have been found near New Zealand and the United States. [4]
The starfish Brisinga endecacnemos was discovered in deep water off Norway in 1856, followed by another abyssal species, Brisinga coronata, now Hymenodiscus coronata . A new order, Brisingida, was erected to accommodate these, consisting of a single family, Brisingidae. Since then dozens of new species have been described from deep water habitats and in 1986, the American zoologist Maureen Downey split the family on morphological and behavioural grounds, creating the new family Freyellidae. [5]
Members of this family have a small, Ophiurida-like disc, clearly demarcated from the arms, which number more than five. The disc is approximately circular with a rim of fused plates which gives rigidity. The madreporite is near the margin of the disc. The arms are long and tapering with the ratio of the arm length to the disc radius being greater than 6/1. There is an acute angle between the arms . After a narrow cylindrical portion, the part of the arms closest to the disc accommodates the gonadal tissues and widens out somewhat. Beyond this area, the arms taper to a long point. In all these aspects members of this family resemble members of Brisingidae, the other family in the order Brisingida. They differ from Brisingidae in having the interradial arcs curved, having smaller madreporites, having bare interadial plates on the disc, having the aboral (upper) surface of the arms continuous with the disc, and having the plates on the proximal parts of the arms abutting rather than overlapping each other. [5]
Members of Freyellidae are usually found on soft substrates at depths between 950 and 5,600 m (3,100 and 18,400 ft). This is a greater depth than Brisingidae, which occurs between 100 and 4,000 m (300 and 13,100 ft), usually on hard surfaces. Because of the way their plates abut on the proximal ends of their arms, Freyellids have not been observed to raise their arms vertically above their discs, as do Brisingidae, and some are probably not suspension feeders. Some do however raise the distal portions of their arms, the parts beyond the gonadal regions. [5]
The World Asteroida Database lists the following genera and species: [2]
Asterias is a genus of the Asteriidae family of sea stars. It includes several of the best-known species of sea stars, including the (Atlantic) common starfish, Asterias rubens, and the northern Pacific seastar, Asterias amurensis. The genus contains a total of eight species in all. All species have five arms and are native to shallow oceanic areas of cold to temperate parts of the Holarctic. These starfish have planktonic larvae. Asterias amurensis is an invasive species in Australia and can in some years become a pest in the Japanese mariculture industry.
The Valvatida are an order of starfish in the class Asteroidea, which contains 695 species in 172 genera in 17 families.
The Echinasteridae are a family of starfish in the monotypic order Spinulosida. The family includes eight genera and about 133 species found on the seabed in various habitats around the world.
The Asterinidae are a large family of sea stars in the order Valvatida.
Astropecten is a genus of sea stars of the family Astropectinidae.
The Asteriidae are a diverse family of Asteroidea in the order Forcipulatida. It is one of three families in the order Forcipulatida.
Coscinasterias is a genus of sea stars of the family Asteriidae.
Goniasteridae constitute the largest family of sea stars, included in the order Valvatida. They are mostly deep-dwelling species, but the family also include several colorful shallow tropical species.
The Brisingids are deep-sea-dwelling starfish in the order Brisingida.
Henricia is a large genus of slender-armed sea stars belonging to the family Echinasteridae. It contains about fifty species.
Solaster is a genus of sea stars in the family Solasteridae.
The Brisingidae are a family of starfish found only in the deep sea. They inhabit both the Atlantic and Pacific Oceans at abyssal depths, and also occur in the Southern Ocean and around Antarctica at slightly shallower depths.
Mediaster is a genus of starfish in the family Goniasteridae. It was circumscribed in 1857 by William Stimpson for M. aequalis, the genus's type species. Its junior synonym is the genus Isaster, which was circumscribed in 1894 by Addison Emery Verrill for the species now known as M. bairdi. Verrill himself synonymized the two genus names in 1899.
Pteraster is a genus of sea stars in the family Pterasteridae.
Brisinga is a genus of starfish in the family Brisingidae. The species in this genus are primarily found in deep sea habitats.
Freyella is a genus of deep-sea-dwelling starfish in the order Brisingida.
Freyella elegans is a species of deep-water starfish in the family Freyellidae in the order Brisingida, living at abyssal depths in the northwestern Atlantic Ocean.
Novodinia is a genus of echinoderms belonging to the family Brisingidae.
Ophidiaster is a genus of echinoderms belonging to the family Ophidiasteridae.
Lophaster is a genus of starfish within the family Solasteridae.