Ochre Sea Stars (Pisaster ochraceus)

Contributed by Dr. Bonnie Becker

Where found: Throughout the intertidal, although never much above the water line.

Interesting facts:  Since sea stars are not actually fish, the term “starfish” is technically incorrect. Sea star is the more appropriate term for these invertebrates. These animals are very often found in conjunction with California mussels and gooseneck barnacles. BPT refers to this as the Mytilus-Pollicipes-Pisaster association. Pisaster is noticeably missing from the Cabrillo National Monument tidepools, but is included in this summary due to their ecological importance on most California shores. The reasons they are absent from CNM and the ecological effects of this absence are unknown. If a visitor or volunteer finds one, try to identify it to species (or photograph it) and report it to a ranger.

Adaptations:  Pisaster does not need protective coloration, since they are extremely tough. They have few enemies besides humans, who collect them for souvenirs. They are very strong. To remove a Pisaster from a rock, one needs to rip off its tube feet with a crow bar. On the skin of these echinoderms are little pincers called pedicellariae. These are used to keep parasites like barnacles from growing on the animals. They have also been used for feeding, catching a small crab and moving it towards the tube feet. The tube feet and other tiny extensions on the sea star’s body aid in breathing.

Food:  Pisaster is a voracious eater and will ingest anything it can fit in its stomach. It eats by inverting its stomach and digesting its food outside the stomach. Sea stars will wrap around a mussel or other bivalve, pry the shell apart, and insert their stomach inside. They can fit their stomachs into a slit that is only 0.1mm wide.

 Life history:  Spawning occurs in April and May on the Central Coast. They grow in proportion to their food supply, and will actually shrink when the food supply is too low. They are thought to live up to 20 years.

Classification:
Phylum:           Echinodermata (Sea stars, Brittle Stars, Sea Urchins, Sea Cucumbers, Sand Dollars, etc.)
Class:              Asteroidea (Sea stars)
Order:             Forcipulatda
Family:            Asteriidae

Last revised 26-Aug-14