Invertebrates

Anthopleura elegantissima/ sola

Haliotis cracherodii

Lottia gigantea

Mytilus californianus

Chthamalus spp./ Balanus glandula

Tetraclita rubescens

Pollicipes polymerus

Pisaster ochraceus

Algae

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Pisaster ochraceus Brandt, 1835

Ochre sea star

General Description (from Morris et al. 1980):

Average arm radius in Monterey Bay 14 cm, occasionally twice this size; usually 5 arms in number but varying from 4 to 7; aboral surface with many small white spines arranged in detached groups or in a reticulate pattern, generally forming a star-shaped design on central part of disk; color yellow or orange to dark brown or deep purple

Habitat and Range (from Morris et al. 1980):

Common, middle and low intertidal zones on wave-swept rocky shores; subtidal on rocks to 88 m; juveniles in crevices and under rocks, seldom seen in central and southern California; Prince William Sound (Alaska) to Point Sal (Santa Barbara Co.)

Biology:

Ochre sea stars have a wide diet, including barnacles, snails, limpets, and chitons, however, mussels are the primary prey item (Morris et al. 1980). Using their tube feet to pull apart the valves, Pisaster are able to evert their stomachs and insert them between the valves of a mussel, (Morris et al. 1980). Interactions between Pisaster and their prey have been well researched (Paine 1966, 1974; Dayton 1971), and motile prey have been known to elicit escape responses to the chemical presence of Pisaster (Morris et al. 1980). Seagulls, sea otters, and humans are the few predators of sea stars. Sea stars are able to regenerate arms that may have been lost. Pisaster are thought to live up to 20 years (Morris et al. 1980). Recovery from oil spills is expected to be long, although Pisaster were not visibly affected by an oil spill (Chan 1973).

Can be confused with: Pisaster giganteus, which has fewer, bigger, and longer aboral spines surrounded by blue rings. The spines are more uniformly spaced and never form a star-shaped pattern (Morris et al. 1980).

Pisaster giganteus (Photo: Aimee Bullard)

Pisaster giganteus spine detail

References:

Chan GL (1973) A study of the effects of the San Francisco oil spill on marine organisms. In Proceedings of joint conference on prevention and control of oil spills. American Petroleum Institute, Washington, D.C., pp 741-782

Dayton PK (1971) Competition, disturbance and community organization: the provision and subsequent utilization of space in a rocky intertidal community. Ecol Monogr 41:351-389

Morris RH, Abbott DL, Haderlie EC (1980). Intertidal invertebrates of California. Stanford University Press, Stanford

Paine RT (1966) Food web complexity and species diversity. Amer Nat 100:65-75

Paine RT (1974) Intertidal community structure: experimental studies on the relationship between a dominant competitor and its principal predator. Oecologia 15:93-120