Ochre Stars

• ecologíaIt is a keystone predator: removing it experimentally from a stretch of shore caused a documented collapse in local biodiversity, and the whole ecological concept was described from that work.
• It is the species that gave rise to the concept of a keystone species. In 1966 Robert Paine removed every one of these sea stars from a stretch of Washington coast and watched what happened: mussels took over the rock and diversity collapsed from fifteen species to eight.
• That experiment changed ecology: it showed that a single predator can sustain the diversity of an entire community, and the term keystone species is now used worldwide.
• It feeds mainly on mussels. It opens them by pulling the valves apart with its tube feet, pushes its stomach out through its mouth and inserts it through a gap less than a millimetre wide to digest the prey inside its own shell.
• It has also suffered wasting syndrome, although it has recovered better than the sunflower sea star.
• Its colour varies between ochre, orange and purple, and depends not on genetics but largely on diet.

Skeleton type

Invertebrate - internal calcareous endoskeleton made of plates (ossicles)

Habitat & environment

Wave-beaten rocks of the mid-intertidal of the north-eastern Pacific, from Alaska to Baja California; it withstands hours out of the water

Sources consulted: https://es.wikipedia.org/wiki/Pisaster_ochraceus