black dot
   
  Feeding, growth, & regeneration
  The topic of prey resources is considered here, while LARVAL FEEDING, ADULT FEEDING, ENVIRONMENTAL EFFECTS ON FEEDING, INGESTIVE CONDITIONING, and GROWTH & REGENERATION are considered in other sections.
  black dot
 

Prey resources

 

This section on prey resources deals with genera P-R, while GENERA A-H, GENERA L-O, and GENERA S-Z are considered in other sections.

  black dot
 

Genera P-R: Pateria

 
Research study 1
 

Bat stars Pateria miniata are omnivorous scavengers of plant and animal matter.  In the field individuals are commonly observed with their voluminous cardiac stomachs everted and widely spread over the substratum.  Food items are enveloped by the stomach folds and transported into the cardiac stomach. Even small soft bits that could be ingested immediately are first covered and wrapped in stomach folds before being moved into the gut cavity for further digestion.  Bits of kelp and other seaweeds, and live prey such as limpets appear to be digested in situ in the folds of the stomach.  The powerful digestive enzymes, produced in the pyloric caeca and moved to the stomach by ciliary action, digest small shellfishes and sea stars within 1-photograph of a bat star Patiria miniata with partially everted stomach2d.  The stomach is so baggy and voluminous that it appears to require a more elaborate retractor harness than found in other sea-star species.  The retractor muscles originate in each arm and are connected to retractor bands that subdivide several times to enclose the entire stomach.   Each band ultimately spreads to 64 widely dispersed terminal attachments at the outer folds of the stomach.  In total, there are 320 ultimate points of attachment of the retractor strands to the stomach that enable it to be retracted.   Anderson 1959 Biol Bull 117: 185.

NOTE the author does not provide a diagram of this interesting arrangement


Bat or cushion star Patiria miniata with
partially everted cardiac stomach 1X

 
Research study 2
 

In southern California Patiria miniata feeds on bryozoans Tubulipora tuba and T. pacificaDay & Osman 1981 Oecologia 51: 300.

   
 
Research study 3
 

photograph of sea urchin Lytechinus anamesus courtesy Peter Bryant, University of California, Irvinegraph showing numbers of sea stars Patirial miniata and sea urchins Lytechinus anamesus in kelp beds around San Clemente, CaliforniaAlso in southern California around San Clemente, Patiria miniata is a predator of sea urchins Lytechinus anamesus.  In and around kelp beds of Macrocystis pyrifera the distribution of the 2 species is reciprocal, with Patiria generally being abundant where Lytechinus is in low numbers, and vice versa (see graph upper Right).   However, in another nearby location (data not shown), the distributions graph showing escape response (movement away) by sea urchins Lytechinus anamesus after being touched by predatory sea star Patiria miniata are more or less reversed, with Lytechinus being abundant offshore from the kelp bed and Asterina being rare. 

Laboratory studies show that Patiria elicits an escape response from Lytechinus that is strongly correlated with size of urchin (see graph lower Right).  Small urchins run only a short distance after being contacted by the sea star, while larger urchins run further.  Other experiments show that when placed together in a cage with Patiria for 3wk, small urchins (<15mm test diameter) suffer over 4 times greater mortality than large urchins (>15mm test diameter). Field observations show that in areas where Patiria is abundant, Lytechinus have moved away.  The authors suggest that predation on young urchins by Patiria, combined with forced emigration of older urchins, may have long-term beneficial effects on the kelp-forest community by allowing kelp sporlings a greater chance to flourish.  Schroeter et al. 1983 Oecologia 56: 141. Photograph courtesy Peter Bryant, Univ California, Irvine.

NOTE  the lower graph shows distance moved after being touched by the tip of a sea-star ray for 3min duration; control data are distances moved after being touched with a glass rod (generally no response). Some sea urchins are unresponsive to the sea stars and move small distances or not at all

 
Research study 4
 

graph of predicted areas of sea bottom left ungrazed by sea stars Patiria miniata at different densities of individualsThe manner in which bat stars Patiria miniata feed by everting their stomachs voluminously over the sea bottom means that a variety of organic matter is digested1, including some plants.  A large-scale study involving removal/addition of Patiria in kelp beds in Carmel Bay, California shows that bat-star grazing can significantly reduce survival of giant kelps Macrocystis pyrifera up to the age of 7wk-old sporophytes.  At a height of 1-3cm the kelp sporophytes reach a refuge in size from bat-star grazing.  A model developed from grazing parameters2 photograph of several bat stars Patiria miniataobtained during the field study indicates that theoretical bat-star densities3 of 9-18 . m-2 would leave less than 1% of the bottom ungrazed over a 90d period (see graph above).  However, note in the graph that even at these high densities a large portion of the sea bottom would remain ungrazed over the first few weeks, possibly allowing kelp sporophytes to reach size refuge.  The author concludes that while the grazing may not contribute to large-scale differences in density of adult plants, it could contribute to small-scale patterns of dispersion.  Leonard 1994 J Exp Mar Biol Ecol 179: 81.


NOTE1 the sea star obtains nutrition from bacteria, detritus, encrusting animals, algal spores, plants, and other organic matter.  Patiria’s digestive enzymes apparently can break down cellulose, the main constituent of cell walls of plants

NOTE2  these include Patiria densities, radius of extruded stomach, and number of feeding spots occupied both day and night, and over time

NOTE3  normal Patiria densities in the kelp-bed area range from 3-4 . m-2

  black dot
 

Pisaster

  These entries are arranged alphabetically by species, starting with P. brevispinus, then chronologically for each species.
 
Research study 1
 

photograph of sea star Pisaster brevispinus just uprooted from its digging for a clam
Sea stars Pisaster brevispinus mainly prey on buried clams which they dig up by slow excavation of the sediments. A "foraging bowl" created by Pisaster brevispinus may be 70cm in diameter by 10cm deep. It is fashioned by the sea star’s tube feet pushing particles of sand and gravel along each arm to form piles at the arm tips.  There is enormous elongation of the tube feet around the mouth.  Smith 1961 Behaviour 18: 148.

 

 

 

Sea star Pisaster brevispinus interrupted in its digging for a clam.
The clam must have been close to being caught as evidenced by the
extruded cardiac stomach. Note the greatly elongated oral tube feet
able to reach a considerable distance into the sand 0.5X

 
Research study 2
 

photograph of a sea star Pisaster brevispinus eatin a clam Humilaria kennerleyi
In Puget Sound, Washington Pisaster brevispinus eats mainly clams, including Saxidomus giganteus, Protothaca spp., Humilaria kennerleyi, and sometimes barnacles Balanus nubilis. Mauzey et al. 1968 Ecology 49: 603.

 

 

 

 

 

 

Pisaster brevispinus attacking a
clam Humilaria kennerleyi 0.7X

 
Research study 3
 

photograph of a close view of tube feet of a sea star attached to a clam Humilaria kennerleyi
The pink sea star Pisaster brevispinus is mainly found on subtidal sandy/mud or shell-gravel substrates.  In the Bodega Bay region of California its prey consists of barnacles, worms, and bivalves including Macoma spp., and juvenile horse clams Tresus capax and T. nuttallii (0.5-2.5cm shell length).  A common feature of a foraging P. brevispinus is the cluster of greatly elongated tubefeet extending from the region around the mouth.  The tubefeet can extend to a length of one radius, or about 8-10cm for an average-sized adult sea star.  The tube feet force their way through the sand to the prey, attach to it, and pull it up to the mouth.  Van Veldhuizen & Phillips 1978 Mar Biol 48: 89.




Tube feet of Pisaster brevispinus attached
to a prey bivalve Humilaria kennerleyi 2X

 
Research study 4
 


drawings of burrowing modes of sea stars when seeking out bivalve preyOn a British Columbia sandbed in winter Pisaster brevispinus is recorded to  eat barnacles on hard surfaces and large bivalves which it excavates in sand up to 40cm in depth.  Of 24 bivalves eaten in one study, 16 are Solen sicarius, 5 are Panope abrupta, and 3 are unidentified. Sloan & Robinson 1983 Ophelia 22: 125.

 
Research study 5
 

photograph of sea star Pisaster giganteus courtesy NOAA Channel Islands Marine Sanctuary, California
Pair-wise tests on feeding preferences of Pisaster giganteus collected around Santa Barbara, California show the following preference hierarchy: mussels Mytilus trossulus and M. californianus > ribbed mussels Septifer bifurcatus > whelks Nucella emarginata > spiny whelk Acanthina spirata, turban shells Tegula funebralis, and chitons Nuttallina californica.  Landenberger 1968 Ecology 49: 1062. Photograph courtesy NOAA Channel Islands National Marine Sanctuary, California.

 
Research study 6
 

photograph of snail Kelletia kelletii courtesy Gerald and Buff Corsi (Copyright) California Academy of SciencesPisaster giganteus inhabits rocky west-coast coastlines from southern Vancouver Island, British Columbia to Baja California.  In the San Diego area of California it is recorded to eat 32 different prey species, with bivalves and gastropods making up about 80% of the total.  One of these prey species is the snail Kelletia kelletii (representing about 10% of Pisaster’s diet), which itself eats several of the same prey species as P. giganteus, and is sometimes found eating the same prey item at the same time as the sea star. Rosenthal 1971 Fish Bull 69: 669. Photograph courtesy Gerald and Buff Corsi © California Academy of Sciences.

 

 

The snail Kelletia kelletii, one of only 2 buccinid species
occurring in California, is a scavenger and predator 0.6X

 
Research study7
 

photograph of an ochre star Pisaster ochraceus eating goose barnaclesOchre stars Pisaster ochraceus consume many different prey species, but show an obvious preference for acorn barnacles and, to a lesser extent, mussels. Here are some data for different west-coast areas:

On the California open coast Pisaster ochraceus eats:
Barnacles                                      61%
Bivalves (mostly Mytilus spp.)        18
Limpets                                          4
Snails                                             8
Chitons                                           5
Other                                             4
Feder 1959 Ecology 40: 721.

In Mukkaw Bay, Washington, the following prey are eaten (over 1000 feeding observations):

acorn barnacles (3 spp.)       59%
bivalve (mussels)                 25 
limpets (2 spp.)                      5
goose barnacles                      6
chitons (2 spp.)                      3
Nucella ostrina (whelk)           1           
Other                                    1 

photograph of ochre star Pisaster ochraceus eating a sea mussel Mytilus californianusPisaster ochraceus caps a subweb that also includes the predatory whelk Nucella ostrinaPaine 1966 Am Nat 100: 65.

In San Juan Islands, Washington Pisaster ochraceus eats:

Barnacles                                      50%
Bivalves (mostly Mytilus spp.)        12
Limpets                                        18
Snails                                           10
Chitons                                          8
Other                                             2
Mauzey et al. 1968 Ecology 49: 603.

NOTE data are from examination of 3820 specimens over a 22-mo study period.  Of these, 1364 individuals are feeding (35%).  However, since one sea star may feed on more than one prey at a time, the total prey items is 1557

Summer diets of Pisaster ochraceus at 3 sites in Barkley Sound, British Columbia consist mostly of acorn barnacles (Balanus glandula and Semibalanus cariosus), and mussels (Mytilus trossulus and M. californianus; see pie diagrams below).  To some extent, the sea stars’ preferences correspond to prey densities in the habitats.  The major exception is large M. californianus (>4cm in length), which tend not to be eaten by Pisaster.
Robles et al. 1995 Ecology 76: 565.
 pie diagrams showing prey eaten by ochre stars Pisaster ochraceus at 3 locations in Barkley Sound, British Columbia

 

 

  black dot
 

Poraniopsis

 
Research study 1
 

photograph of sea star Poraniopsis inflata courtesy Roland Anderson and Seattle Aquarium
The sea star Poraniopsis inflatus is rarely seen, yet is broadly distributed from Alaska to southern California, and is sometimes found in shallow water (3-17m depth).  Its field diet is not known, but laboratory observations on a single specimen collected in Puget Sound, Washington suggest that sponges such as Halichondria sp. and Suberites sp. may comprise the main dietary items.  Anderson & Shimek 1993 Zoo Biol 12: 499. Photograph courtesy Roland Anderson and Seattle Aquarium.

 

 

 




Sea star Porites inflatus appears
to be mainly a spongivore 0.6X

  black dot
 

Pteraster

 
Research study 1
 

photograph of sea star Pteraster tesselatus with sponge
In Puget Sound, Washington Pteraster tesselatus feeds on various prey in accordance with their availability in the habitat, e.g., sponges, ectoprocts, anemones, ascidians, and bivalves. Mauzey et al. 1968 Ecology 49: 603.

 

 

 




Slime star Pteraster tesselatus 0.5X

  black dot
 

Pycnopodia

 
Research study 1
 

Dietary preferences for sunflower stars Pycnopodia helianthoides vary with area:

In San Juan Islands, Washington (125 feeding observations combined from several studies):
clams (mainly Saxidomus giganteus)                         63%       
Strongylocentrotus spp. (sea urchins)                        23
other (snails, limpets, crabs, holothurians, sea stars)  14

On the open coast of Washington (144 feeding observations combined from several studies):
clams                                                                        2%
Strongylocentrotus spp.                                           93
other (snails, limpets, crabs, holothurians, sea stars)  5
photograph of sunflower star Pycnopodia helianthoides digging for a clamMauzey et al. 1968 Ecology 49: 603.

In Prince William Sound, Alaska (425 stomach analyses) the diet consists predominantly of:
mussels 84%
clams 9%
small gastropods 6%.
Many other species are also eaten (up to 70 different prey items are recorded from a single Pycnopodia stomach).  Paul & Feder 1975 Ophelia 14: 15.

On a British Columbia sandbed in winter Pycnopodia helianthoides grazes epifauna on hard surfaces, excavates large bivalves on sand, and hunts down cockles.  Of 10 bivalves eaten, 6 are Clinocardium nuttallii and 4 are Panope abrupta. Sloan & Robinson 1983 Ophelia 22: 125.

Sunflower star Pycnopodia
helianthoides
digs for a clam 0.5X

 
 
photograph of a large sunflower star Pycnopodia helianthoides eating a red urching Strongylocentrotus franciscanus

CLICK HERE to see a video of a SCUBA-diver collecting a large sunflower star and then turning it over to show a partly digested red urchin Strongylocentrotus franciscanus in the sea-star's mouth.

NOTE  the video replays automatically

 
Research study 2
 

drawing of a sunflower star Pycnopodia helianthoides with recently ingested squid pens emerging from the aboral surfaceSunflower stars Pycnopodia helianthoides in Monterey Bay, California may find seasonally abundant prey in the form of post-spawning moribund/dead squids Doryteuthis opalescens.  A squid is ingested whole by a photograph of several broken squid pensPycnopodia within 10min.  The interesting thing is that the indigestible but cleaned pen1 of the squid may end up protruding from the aboral surface of the sea star. In an experiment where 26 Pycnopodia are kept in mesh baskets at 12m depth and fed on squids for a 4-mo period, 7 such protrusions2 are recorded, each occurring within an average of 38h from ingestion. The drawing on the Left shows the location of each of the 7 pens.  It is not uncommon for a pen to protrude from a dermal papula3.  While the author does not report seeing a pen actually drop out of a sea star’s body, several sea stars are observed to wrap their arms around the pen as if to pull them out.  If these arms are manually unfastened, the sea star re-establishes contact with its arms within a few hours.  Wobber 1973 Veliger 16: 203.

NOTE1  the pens are approximately 15cm x 2cm in size

NOTE2  for this to happen the pen has to penetrate the wall of the gut, pass through the coelomic cavity, and penetrate the aboral body wall (which is quite soft in Pycnopodia).  If this were to happen in a vertebrate, septicemia would result with a good chance of it leading to death.  In the absence of a circulatory system in echinoderms, the coelomic fluid functions in gas and nutrient transport, and also carries elements of internal defense.  Instead of antibodies to fight infection, as in vertebrates, there are similarly functioning protein entities known as haemaglutinins that circulate in the coelomic fluid, along with phagocytic cells for engulfing "non-self" protein.  These systems are considered more primitive than comparable internal defensive systems in vertebrates, but clearly they work well enough in these circumstances to prevent or minimise infection. The author does not mention any sea stars dying from these piercings

NOTE3  soft-skinned gas-exchange protrusions on the surface of many sea stars.  Each papula communicates directly with the body coelom        

 
Research study 3
 

table showing prey species of sunflower stars Pycnopodia helianthoides, both intertidal and subtidalIn Torch Bay, Alaska (473 feeding observations over a 5-yr period) prey preferences of Pycnopodia helianthoides differ substantially whether subtidal or intertidal. Subtidally, sea urchins comprise 66% of the prey, while intertidally, mixed gastropods and Mytilus trossulus comprise about 79% of the prey. Duggins 1983 Ecology 64: 1610.


 
Research study 4
 

map showing collecting sites for sunflower stars used in a study of dietary preferences
Observations on, and gut analyses of, 300 Pycnopodia helianthoides in Barkley Sound, British Columbia indicate that 220 have recently eaten.  Prey items include representatives from 11 major taxa, but with no one taxon dominating.  Numerous species of snails, bivalves, and crustaceans are represented.  Butter clams Saxidomus giganteus respresent only 2% of total prey items (in total, 10 species of bivalves are eaten).  Similarly, although 2 sea-urchin species photograph of a sunflower star Pycnopodia helianthoides eating an octopus armco-occur in the habitat, they represent only 5% of prey items.  Interestingly, although sunflower stars are generally not limited to a certain size of prey because they can feed “extra-orally”, the authors show a significant correlation between sea-star size and prey size.  Carcasses of birds, dogfishes, herring, octopuses, and even other sea stars are included in the entries, underscoring the generalist nature of Pycnopodia’s feeding.  Shivji et al. 1983 Pac Sci 37: 133.

 

Sunflower star Pycnopodia helianthoides eats
an octopus arm that it has scavenged 1X

 
Research study 5
 

Abalone Haliotis spp. are rarely listed as prey of sunflower stars Pycnopodia helianthoides, but this is not for lack of attention by the sea star. A sunflower star will attempt to run down an abalone at every opportunity but, owing to the abalone's superior speed and habit of twisting its shell violently on contact with the predator, the prey is rarely caught.

 

photograph of sunflower star Pycnopodia helianthoides beginning to chase an abalone Haliotis kamtschatkana
photograph of sunflower star Pycnopodia helianthoides beginning to chase an abalone Haliotis kamtschatkana
On first encounter with the sea star the abalone Haliotis kamtschatkana swivels around and starts crawling quickly away A moment later the abalone is well on its way to safety, as it can easily outrun a pursuing sunflower star
 
Research study 6
 

Sea stars, such as sunflower stars Pycnopodia helianthoides, use water-borne chemical cues to locate their prey.  Damaged prey release more chemical cues than intact ones, and thus are predicted to be more attractive to foraging predators.  The role of current in food-finding in P. helianthoides is investigated in Kachemak Bay, Alaska, uniquely using in situ choice chambers of several designs.  In one such experiment to determine if P. helianthoides uses chemoreception to locate damaged or dead prey, a Y-maze apparatus of “standard” design is employed, with an intact clam Saxidomus giganteus on one side and a damaged clam on the other.  Results show that 83% of 40 sea stars tested move to the side containing the damaged clam, and only 2% to the side containing a live control clam.  Interestingly, in a test of live clam vs. live clam, only 10% of sea stars make a choice (5% vs. 5%), while the remaining 90% are indifferent. Other tests show that Pycnopodia will bypass live prey clams to reach damaged or dead prey.  These and other observations suggest to the authors that P. helianthoides is a facultative scavenger that uses chemoreceptive abilities preferentially to locate damaged or dead prey.  Brewer & Konar 2005 Mar Biol 147: 789.

   
  Sunflower stars will eat most any prey, dead or alive, but when pursuing live prey such as clams, they often expend much time and energy:
 
photograph of sunflower star Pycnopodia helianthoides digging for a clam
Digging for a buried clam
photograph of sunflower star Pycnopodia helianthoides digging for a clam
Digesting a sea urchin that may have been damaged
photograph of sunflower star Pycnopodia helianthoides digging for a clam
Digging for a clam
 
  RETURN TO TOP