Scientific name: Ophiothrix fragilis

(Abildgaard, 1789)

Common Name: Cat: Ofiura; Cast: Ofiura de espinas finas; Fr: Ophiure fragile; Eng: Common brittlestar

Group: 18. Seastars

Area type: Diving and watching under the stones, Cave diving

Depth: Down to 350 m

Measures: Up to 12 cm

How does it look like?

Composed of a central disc, rounded to pentagonal, with five arms coming out of it. Their length is about 5 times the diameter of the disc, which in adult specimens achives a size around 20mm. The ambulacral feet are barely developed. The disc is covered with short tiny spines, arranged in 5 radial groups. Normally the colour is brown or grey, but sometimes it varies from purple to red, yellowish, orange or even white.

Where does it live?

They are found from northern Europe to South Africa. Also at the Mediterranean Sea.

How do they feed?

They feed on particulate matter which they collect with the help of the ambulacral system, located at the ventral part of the arms. The ambulacral system carries the food to the mouth.

How do they reproduce?

Generally Ophiuroidea need two years to become sexually mature. There are males and females. Their eggs are found in bags, where the larvae develop.

Is a confusion possible?

Their can be a confusion with Ophiothrix luetkeni, but this species just presents small dorsal spines. It also can be mixed with Ophiocomina nigra.

Curiosities

· They can live up to ten years

· Their arms are fragile and brake easily. They use them to escape from possible predators by leaving them behind and afterwards they are able to regenerate them back to normal size. That's why we can observe many animals with half-sized arms

· If you take a specimen from the ground and let it fall back, it falls with the arms open. If you do the same with the species Ophiocomina nigra, this falls with their arms folded up

Taxonomy
Class: Ophiuroidea, Order: Ophiurida, Family: Ophiotrichidae