The diet of a given species of sea star depends primarily on geographical location and secondarily on time of year¹, reproductive state², and dietary history³. The intent here is to give an overview of sea-star diets focusing on the first determinant, but keep the other factors in mind as you check out the various species.  The species are treated alphabetically by genus.

NOTE¹  some sea stars, for example, the ochre star Pisaster ochraceus, may eat little or not at all during winter

NOTE²  an individual building gonads during reproductive season may require nutrients in different proportion than at other times, and this may require the consumption of different types of prey.  Since reproduction is generally seasonal on the west coast, this influence on dietary choice may overlap the “time of year” factor.  An extreme example of the effect of reproductive state on diet is the sea star Leptasterias hexactis, females of which are physically incapable of feeding while brooding their eggs

NOTE³  predators that hunt by sight often form “search images” of their prey; that is, a certain species of prey will be singled out over others and, when hunting, the predator will ignore other species in favour of this one.  This increases the predator’s efficiency in a "practise-makes-perfect" sort of way.  Sea stars hunt by olfaction and touch, but the same concept applies.  An related factor that greatly influences diet choice in an animal is “ingestive conditioning”.  Here, just as for vertebrates, what a sea star has eaten previously will influence what it will later select.  A sea star may avoid a food that has a bad taste or that produces a negative post-digestive effect.  Conversely, a food that satisfies these needs may be favoured  

The diet of Crossaster papposus varies greatly depending upon locality:

Auke Bay, Alaska (369 feeding observations):
Chlamys rubida (scallops) 81%
bivalves/snails/chitons 6
echinoderms (green urchins, sea stars, Leptasterias) 4
other (cnidarians, crustaceans, fishes, unidentified) 9
Carlson & Pfister 1999 Mar Biol 133: 223.

Puget Sound, Washington (131 observations):
Ptilosarcus guernyi (sea pens) 50%
opisthobranchs (mostly Hermissenda) 34
algae 12
Mauzey et al. 1968 Ecology 49: 603.

NOTE  for comparison, here are some data for C. papposus in the Mingan Islands, Gulf of St. Lawrence: 
sea urchins 51%
sea stars 7
mussels 3
miscell 39 
Gaymer et al. 2004 J Exp Mar Biol Ecol 313: 353.

These 3 oral views show an attack by Crossaster papposus on a bivalve, starting with tube-feet attachment, partial cardiac-stomach extrusion to surround the prey, and after a few hours almost complete enclosure of the prey in the stomach.  Hancock 1974 Ophelia 13: 1.

Dermasterias

Diets of leather stars Dermasterias imbricata vary with locality:

Puget Sound, Washington (41 feeding observations):
anemones/holothurians/sea pens 95%
ascidians 5
Mauzey et al. 1968 Ecology 49: 603.

San Juan Islands, Washington (100 observations):
holothurians (mostly Cucumaria lubrica) 96%
Mauzey et al. 1968 Ecology 49: 603.

Pt. Loma, California (68 individuals):
sea urchins S. purpuratus 63%
Rosenthal & Chess 1970 Fish Bull 70: 205.

Pt. Loma, California (437 individuals):
sea urchins (S. purpuratus) 47%
sea stars 4
sponges 15
detritus 27
miscellaneous 7
Rosenthal & Chess 1972 Calif Fish Game 56: 203.

Monterey Bay, California (243 observations at 2 sites):
Corynactis californica (corallimorpharian) 73%
Anthopleura elegantissima (sea anemone) 3
hydroids 2
bryozoans 7
algae 9
Strongylocentrotus purpuratus (sea urchin) 1
other (hydroids, sponges, sea urchins, chitons) 10
Annett & Pierotti 1984 Mar Ecol Progr Ser 14: 197.

A leather star Dermasterias imbricata competes
with a red sea urchin for a meal of dead fish 0.5X

The corallimorpharian polyp Corynactis californica is the most abundant prey species of leather stars Dermasterias imbricata in habitats studied around Monterey Bay California, and is the predominant prey eaten (see histogram on Left).  When given a choice in the lab, however, Dermasterias prefers to eat aggregating anemones Anthopleura elegantissima and avoids Corynactis entirely, perhaps because of toxic stings to its sensitive dermal papulae.  Annett & Pierotti 1984 Mar Ecol Progr Ser 14: 197.

NOTE  lit. “skin pimples” G., referring to the thin-skinned protrusions on the upper surfaces in sea stars that function like gills in exchanging gases for metabolism (also known as dermal branchiae or “skin gills”)

Corynactis californica displays its
toxic nematocyst batteries 2X

Evasterias

In 229 feeding observations in the Puget-Sound, Washington region Evasterias troschelii is noted to eat the following:
barnacles                                  46%
tunicates                                  17
bivalves                                    23
other (gastropods, polychaetes, brachiopods)         7
Mauzey et al. 1968 Ecology 49: 603. Photograph courtesy Dave Cowles, Walla Walla University, Washington rosario.wallawalla.edu.

In soft-bottom habitats around the San Juan Islands, Washington, tunicates Chelyosoma productum, Styela gibbsii, Pyura haustor, and Boltenia villosa grow in mixed clumps and are preyed upon by sea stars Evasterias troschelii.  In laboratory-choice experiments at the Friday Harbor Laboratories, Washington the sea star prefers the softer-bodied C. productum over the more leathery textured P. haustor and S. gibbsii (see graph). The softer species can be torn apart and consumed directly, while the other 2 species must be consumed through holes digested in their tunics.  In either case, the sea star consumes only the soft inside tissues, leaving the tunic more or less intact. 

When sea stars are caged with mixed clumps of the 4 ascidian species over a 30-d period in the field, the pattern of consumption agrees with that obtained in the laboratory experiments. As in the laboratory experiments, the sea stars eat the tunicates in accordance with the toughness of their tunics, and show no preference for one size or another.  Based on laboratory and field data, the author concludes that E. troschelii is capable of altering the relative abundances of ascidian species in the type of area studied.  Young 1985 p.577 In, Echinodermata (Keegan & O’Connor, eds.) AA Balkema, Rotterdam.

NOTE  on hard-bottom sites in this area, 7 out of 10 feeding E. troschelii are eating molluscs (clams and slipper limpets) and barnacles (mainly Balanus nubilus), while 3 out of 10 are eating ascidians (Chelyosoma productum and Pyura haustor).  In comparison, on mud-bottom habitats 13 of 14 feeding individuals are eating ascidians (C. productum, P. haustor, and Styela gibbsii).  The 14th individual is recorded as eating a clam. Although up to 8 species may be present in these clumps, the 4 species listed comprise 90% of the total

Absence of arms seems to be no obstacle
to growth of this Evasterias troschelii 0.7X

Henricia

A study on Henricia leviuscula at Hopkins Marine Station, Pacific Grove, California provides information on the structure and functioning of its digestive system.  Much of the presentation is too detailed to present here, but one point of interest concerns the Tiedemann’s bodies or pouches, located on the lower part of each pyloric caecum near to where the duct of the pyloric caecum joins the pyloric stomach. The author describes their structure as consisting of numerous flagellated chambers leading into the pyloric caecum.  The author proposes that their function is to pump fluid from the pyloric stomach into the pyloric caeca and to maintain circulatory efficiency within these organs.  The author does not personally observe the feeding process in Henricia, but reiterates the belief that members of the species subsist on suspended particles gathered by a ciliated-mucus mechanism.  Points in support of this include the small size and “doubtful” eversibility of the cardiac stomach (but see Research Study 2 below), and the high degree of specialisation of mechanisms for maintaining flagellary circulation mentioned above. Both suggest a dependency upon suspended particulate matter rather than carnivore-type macrophagy for nutrition.  In support of this idea the author describes feeding by 2 specimens of H. sanguinolenta on a suspension of mussel sperm, where streams of sperm can be seen moving from the ambulacral grooves into the open mouths of the sea stars, with sperm later being found within the Tiedemann’s pouches.  Anderson 1960 Biol Bull 119: 371.

Blood star Henricia leviuscula draped over
a selection of tunicates. possibly feeding 1X

Of 161 blood stars Henricia leviuscula observed feeding in Puget Sound, Washington the stomach is extruded onto sponges/ectoprocts 40% of the time.  This species is usually considered to be a ciliary plankton feeder, but clearly some macrophagy is also exhibited. Mauzey et al. 1968 Ecology 49: 603.

Blood star Henricia leviuscula draped over
some sponges, worms, and other invertebrates.
The nudibranch is Doris montereyensis 0.7X

Other photos of Henricia spp. in different feeding postures:

Hippasteria

Out of 1028 observations in Puget Sound, Washington Hippasteria spinosa is recorded as feeding on Ptilosarcus guernyi 99% of the time.  Mauzey et al. 1968 Ecology 49: 603. Photograph courtesy Randy Shuman.

Sea star Hippasteria spinosa 0.7X