Ophiura albida

Background

Ophiura albida has a central disc reaching about 1.5 centimetres in diameter and five arms up to 6 centimetres long. The disc is flattened, with the upper surface covered in small plates that are mostly brick red, except for white plates at the edge near the arms.

The arms are slender, fragile, segmented, and gradually tapering, with each segment bearing three short spines that lie flat on the surface. Small pores between the plates help distinguish this species from the similar Ophiura ophiura. The underside of the disc is pale, with a central mouth fringed with teeth.

This species is found at depths down to about 200 metres, or 850 metres according to one authority, on soft substrates including coarse sand, fine sand, gravel, and muddy sand. Its range extends from Norway to the Mediterranean Sea and the Azores, and it is common around the coasts of the British Isles, where densities can reach 900 individuals per square metre.

Ophiura albida is a predator and scavenger, feeding on small invertebrates such as polychaete worms, crustaceans, and bivalve molluscs. In the Baltic Sea, it is the favourite food of the starfish Luidia sarsi, and in the Irish Sea it is eaten by the seven armed starfish Luidia ciliaris. Individuals are either male or female, with external fertilisation and planktonic larvae. It is fast-growing and not thought to live more than three years.