The Freyellidae are a family of deep-sea-dwelling starfish. It is one of two families in the order Brisingida. 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.
Taxonomy 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.
Characteristics 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 interradial 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.
Biology Members of Freyellidae are usually found on soft substrates at depths between . This is a greater depth than Brisingidae, which occurs between , 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.
Genera and species The World Asteroida Database lists the following genera and species: Family Freyellidae Genus Astrocles Fisher, 1917 — three species Astrocles actinodetus Astrocles djakonovi Astrocles japonicus Genus Belgicella Ludwig, 1903 — monotypic Belgicella racovitzana Genus Colpaster Sladen, 1889 — two species Colpaster edwardsii Colpaster scutigerula Genus Freyastera Downey, 1986 — six species Freyastera benthophila Freyastera digitata Freyastera mexicana Freyastera mortenseni Freyastera sexradiata Freyastera tuberculata Genus Freyella Perrier, 1885 (synonym: Freyellidea, Fisher, 1917) — 29 species Freyella attenuata Sladen, 1889 Freyella breviispina (H.L. Clark, 1920) Freyella dimorpha Sladen, 1889 Freyella drygalskii (Döderlein, 1928) Freyella echinata Sladen, 1889 Freyella elegans (Verrill, 1884) Freyella felleyra McKnight, 2006 Freyella flabellispina Korovchinsky & Galkin, 1984 Freyella formosa Korovchinsky, 1976 Freyella fragilissima Sladen, 1889 Freyella giardi Koehler, 1907 Freyella heroina Sladen, 1889 Freyella hexactis Baranova, 1957 Freyella indica Koehler, 1909 Freyella insignis Ludwig, 1905 Freyella kurilokamchatica Korovchinsky, 1976 Freyella loricata Korovchinsky & Galkin, 1984 Freyella macropedicellaria Korovchinsky & Galkin, 1984 Freyella microplax (Fisher, 1917) Freyella microspina Verrill, 1894 Freyella mutabila Korovchinsky, 1976 Freyella octoradiata (H.L. Clark, 1920) Freyella oligobrachia (H.L. Clark, 1920) Freyella pacifica Ludwig, 1905 Freyella pennata Sladen, 1889 Freyella propinqua Ludwig, 1905 Freyella recta Koehler, 1907 Freyella remex Sladen, 1889 Freyella vitjazi Korovchinsky & Galkin, 1984 Genus Freyellaster Fisher 1918 — five species Freyellaster fecundus Freyellaster intermedius Freyellaster polycnema Freyellaster scalaris Freyellaster spatulifer
References
Other sources Clark, A.M. and Mah, C. (2001). An index of names of recent Asteroidea, part 4. Forcipulatida and Brisingida, in: Jangoux, M.; Lawrence, J.M. (Ed.) (2001). Echinoderm Studies, 6: pp. 229–347 Mah, C.; Hansson, H. (2013). Freyella Perrier, 1885. In: Mah, C.L. (2013) World Asteroidea database. Accessed through: Freyella Perrier, 1885 at the World Register of Marine Species on 2013-11-25