The Luidia sarsi is a species of starfish. Sand colored with a velvety texture, the species expresses pentamerism or pentaradial symmetry as adults. The five gently tapering arms have conspicuous bands of long white marginal spines in groups of three. Luidia sarsi grow to approximately 20cm across and are found in deeper water (20m+) from Norway to the Mediterranean but in deep colder water in the south. They are usually found on muddy sediment and are most active at night, burying themselves under the sand during the day. Luidia sarsi larva develop from a fertilized egg and are unique in a number of respects. The larva of the species attains an unusual size (up to 35 mm) and a juvenile starfish develops inside the larva. During metamorphosis

Metamorphosis

Metamorphosis is a biological process by which an animal physically develops after birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation...

 the juvenile migrates to the outside and detaches from the swimming larval bipinnaria

Bipinnaria

A bipinnaria is the first stage in the larval development of most starfish, and is usually followed by a brachiolaria stage. Movement and feeding is accomplished by the bands of cilia. Starfish that brood their young generally lack a bipinnaria stage, with the eggs developing directly into...

stage. The larva continues to live separately for several months.