Solaster endeca

Solaster endeca
Scientific classification
Kingdom:	Animalia
Phylum:	Echinodermata
Class:	Asteroidea
Order:	Velatida
Family:	Solasteridae
Genus:	Solaster
Species:	S. endeca
Binomial name
Solaster endeca (Linnaeus, 1771) [1]
Synonyms
Asterias alboverrucosa Brandt, 1835 Asterias aspera O.F. Müller, 1776 Asterias endeca Linnaeus, 1771 Asterias rumphii Parelius, 1768 Solaster endeca decemradiata Sladen, 1889 Solaster galaxides Verrill, 1909 Solaster intermedius Sluiter, 1895 Stellonia endeca L. Agassiz, 1836

Solaster endeca, commons names purple sunstar, northern sunstar, and smooth sun star, is a species of starfish in the family Solasteridae.^[1]

Description

Solaster endeca can grow to about 40 centimetres (16 in) across but 20 centimetres (7.9 in) is a more normal adult size. It is a robust species with nine or ten arms (occasionally any number from seven to thirteen) set around a large disc. The aboral (upper) surface is formed of calcareous plates densely covered with paxillae, peg-like projections covered in tiny spinelets. There are no pedicellariae but there are groups of two to three gills between the plates. On the oral (under) surface, the row of plates on either side of the ambulacral groove bear two or three spines and several rows of shorter spines, and there are two rows of tube feet. Solaster endeca ranges in colour from greyish-cream to pinkish-purple. The arms are often turned up at the tips showing the pale oral (under) surface.^[2] It can be confused with Crossaster papposus , the only British species with a similar number of arms, but Solaster endeca has a smoother aboral surface.^[3][4][5]

Distribution and habitat

Solaster endeca at the New England Aquarium, Boston, Massachusetts

Solaster endeca occurs in the northeastern Atlantic Ocean and the North Sea at depths down to 450 metres (1,480 ft). Its typical habitats are muddy sand, gravel or rocky areas with deposited sediment. It is found in both sheltered and fairly exposed locations.^[4] It also has a circumboreal distribution and is found round the coasts of Greenland, northeastern Canada and the eastern coast of the United States as far south as the Gulf of Maine.^[1] It also occurs in the northeastern Pacific Ocean between northern Alaska and Puget Sound.^[6]

Biology

Solaster endeca is a predator. In the Atlantic Ocean it feeds on other starfish and on bivalve molluscs but in the Pacific its diet is mainly sea cucumbers and other invertebrates.^[6]

In Britain, breeding takes place in the spring. Over a period of about a week, the female lays several thousand eggs in batches. These rise to the surface of the water where they are fertilised by sperm liberated by the male. The developing larvae become less buoyant after three days, feed on the yolks of their eggs, swim with cilia and develop a pair of larval arms. After about eighteen days, they sink to the seabed where each one attaches itself to the substrate with a sucker.^[5] Here it undergoes metamorphosis during which period it develops a disc and first five and then more arms, a pair of tube feet, relatively long spines, red eyespots on the tips of the arms, a mouth and an anus.^[5] After six weeks, the sucker is reabsorbed and the juvenile starfish begins to move about with its tube feet.^[5]

References