Pisaster Ochraceus Class: Asteroidea

Phylum: Echinodermata, Asterozoa

Pisaster ochraceus Class: Asteroidea

Order: Forcipulatacea, Forcipulatida Common Pacific sea star, Family: Asteriidae ochre sea star, purple sea star

Taxonomy: The genus Pisaster includes (95%) purple individuals in British Columbia three Pacific coast sea star species, includ- and Puget Sound, Washington. This variation ing Pisaster ochraceus. One can find many in color could be due to the predominating historic synonyms for P. ochraceus, includ- food source for P. ochraceus in the two ing P. confertus and P. fissispinus for this regions, where mussels are more common in species, but they are not currently used. Washington, Oregon and California but barna- Furthermore, two subspecies were erected cles are the most common food source in Brit- for P. ochraceus in 1996 (Clark) but morpho- ish Columbia and Puget Sound sites (Harley logical and genetic data does not support et al. 2006; see also http:// this designation and, instead, recognizes the echinoblog.blogspot.com/search/label/ single species P. ochraceus (Stickle et al. Pisaster%20ochraceus). 1992; Lambert 2000; Frontata-Uribe et al. General Morphology: Sea stars (Asteroidea) 2008). Before becoming a member of the are conspicuous members of the intertidal genus Pisaster, this species belonged to and subtidal. Their bodies are composed of a the, currently accepted, genus Asterias central disc from which arms or rays extend. (synonyms A. ochracea, A. fissispina, A. ian- The star-shaped body can be divided into the thina, A. janthina, A. margaritifera) or the for- oral (or ventral) side where the mouth is lo- mer genus Asteracanthion (now Asterias). cated and aboral (or dorsal) side. Body: Stiff body morphology that is hard to Description the touch. Size: Average size (Monterey, California) is Rays: Five rays (unless damaged, can 140 mm in diameter, where each ray (arm) range from four to seven rays, Feder 1980). is 40 mm in length (Fisher 1930). The illus- Each ray is tapering, thick, large, not sharply trated specimen is 150 mm in diameter. Pu- demarcated from disc and broadest where get Sound specimens are regularly 250 mm they join the central disc (Dyakonov 1950), in diameter (Kozloff 1993). Weight ranges but not broad enough to give webbed appear- (wet weight) from 37.8–8.34 g (28 animals, ance (as in Patiria spp.). Feder 1970). Central Disc: Large, convex, arched, Color: Aboral (dorsal) surface red, purple, not distinct or as disc-like as in Ophiuroidea brown or ochre (especially on open coast) (brittle stars). Contains (conspicuous) madre- (see Plate 25, Kozloff 1993). Specimens porite (Figs. 1, 3) and (less conspicuous) most commonly purple (Puget Sound, anus. Diameter of disc less than 1/3 body Washington). Oral (ventral) surface ochre. diameter. Juveniles gray with brown aboral patches Aboral Surface: Aboral surface rough in tex- (Feder 1970). Body color may vary with ture and red, purple, brown or ochre in color. geographic region. Harley et al. (2006) Spines: Low, small, serrated, rounded, found more brown (68–90%) and orange (6– bead-like or papillate (Figs. 1, 3). Spines form 28%) individuals in Washington (Olympic crescentic arcs at arm tips. No straight mid- Peninsula), Oregon and California but more

A publication of the University of Oregon Libraries and the Oregon Institute of Marine Biology Individual species: https://oimb.uoregon.edu/oregon-estuarine-invertebrates and full 3rd edition: http://hdl.handle.net/1794/18839 Email corrections to: [email protected]

Hiebert, T.C. and L. Hiebert. 2015. Pisaster ochraceus. In: Oregon Estuarine Invertebrates: Rudys' Illustrated Guide to Common Spe- cies, 3rd ed. T.C. Hiebert, B.A. Butler and A.L. Shanks (eds.). University of Oregon Libraries and Oregon Institute of Marine Biology, Charleston, OR.

dorsal row of arm spines. Spines in center of Tube Feet: Used in locomotion and disc form a distinct star in the illustrated part of water vascular system. Present on specimen (Fig. 1). Two types of spines ventral side in ambulacral grooves where they include: (1) small, clustered around dorsal are staggered in pairs, four rows across and spines and (2) a few solitary, large, sessile down each ambulacral groove (Fig. 4). pedicellariae scattered over dorsal surface Ambulacral Grooves: Grooves are (Fig. 3). long furrows on oral surface of arms, which Madreporite: A sieve-like structure contain tube feet (Figs. 2, 4) (Boolootian which serves as the water intake into the 1966). Along each edge of groove are stone canal is conspicuous about 1/3 of radi- adambulacral spines intermixed with stalked us from center of disc (Fig. 1, between arms clustered pedicellariae (Fig. 4). numbered 1 and 2). Possible Misidentifications Pedicellariae: Among the large five-armed sea Anus: Inconspicuous, near center of stars, Pisaster species are noted for their aboral surface and is surrounded by small thick arms, low papillate dorsal spines and pedicellariae. pedicellariae. Two other Asteriidae species Oral Surface: Oral surface ochre in color share these characteristics: (1) Evasterias and consists of hard, textured extension of troschelii is a low intertidal species with a aboral surface and ambulacral grooves small disc and slender arms compared to P. running the length of each arm and ochraceus and a varied, though generally converging at the mouth. Grooves are more orange-red coloration (Mah 2007). fleshy in texture from presence of tube feet. Evasterias troschelii has clusters of Spines: Spines serrated, blunt, pedicellariae on its adambulacral spines, not heavy and more spine-like than bead-like just at their bases as in P. ochraceus. (2) (Fig. 4). Adambulacral spines (lining ambu- Orthasterias koehleri has sharp dorsal spi- lacral grooves) are articulated, long, thin nes, not blunt papillate ones. These spines (Fig. 4). Three types of spines ventrally: (1) are each surrounded by a distinct ring of small, clustered around bases of oral spines large pedicellariae and the dorsal spines are (Fig. 4); (2) small pedicellariae clustered on arranged in distinct radial rows (those of P. expandable strands between adambulacral ochraceus are not). Orthasterias koehleri is spines (Fig. 4); and (3) large pedicellariae often red with yellow mottling and it occurs in on these same strands (Fig. 4). There are the low intertidal and subtidally (Mah 2007). no pedicellariae on the adambulacral spines Two other species of Pisaster can be (Pisaster, Fisher 1930; Hyman 1955). found locally: (1) Pisaster brevispinus oc- Mouth: Large, in center of disc (Fig. curs not on rocks and pilings but on soft 2). Pisaster species can extrude the stom- substrates, where it feeds on clams. Its ab- ach through this opening, engulfing food and oral spines do not form reticulated patterns initiating digestion externally (Feder 1980). or arcs, but occur singly or in groups of two Pedicellariae: Stalked or sessile ap- or three, and are separated by areas of soft pendages used for removing invaders (e.g. tissue. Pisaster brevispinus has a straight, barnacles larvae) or deterring predators distinct row of mid-dorsal spines on each (e.g. Leptasterias hexactis, Wobber 1975; arm. This sea star is nearly always pink and Solaster dawsoni, Van Veldhuizen and Oa- it can be mottled with gray-green or maroon- kes 1981). Pedicellariae are bird beak-like purple color as well (Mah 2007). It is one of and two-jawed in Pisaster species.

the largest asteroids, growing to 320 mm tion, California and P. o. segnis, which is in diameter (Hyman 1955). (2) Pisaster found south of Point Conception (Clark 1996). giganteus is bluish gray and its dorsal However, these populations are likely a single spines are blunt, clubbed, each species based on morphological and molecu- surrounded by a ring of blue flesh and lar evidence (e.g. Frontana-Uribe et al. 2008). around that a ring of pedicellariae. It has Local Distribution: Locally in Coos Bay and tiny pedicellariae that are thickly scattered along the rocky shores of Cape Arago. Typi- between the dense spines and its spines cally occurs on the open sea coast as well as are not arranged in radial or concentric in bays on jetties and pilings only in marine rows. Pisaster giganteus is a low intertidal parts of large bays. sea star usually found further south than Habitat: Jetties, rocks, pilings, bay mussel Oregon. Despite its name, it is usually beds and hard substrates. Larger individuals smaller than P. ochraceus (Ricketts and can stand prolonged exposure to air (Feder Calvin 1971; Mah 2007). 1970). Body morphology has been shown to Sea stars are extremely variable correlate with wave exposure, where thinner intra-specifically. Fisher listed three forms and lighter individuals are found in areas with (“forma”) of P. ochraceus (Fisher 1930). more intense wave exposure (Hayne and Although these names are not used, Palmer 2013). taxonomically, it should be noted that the Salinity: Collected at salinities of 30 or higher Puget Sound, Washington and Oregon and cannot tolerate long-term exposure to re- outer coast variety of P. ochraceus has a duced salinities. flatter, smoother surface ornamentation Temperature: Cold to temperate. Pisaster than does our Oregon bay form (Roberts, ochraceus is more tolerant to aerial exposure personal communication). Subspecies than other Pisaster species, e.g. P. brevispi- have also been reported for P. ochraceus nus, (up to 50 hours exposure), but does not including P. o. ochraceus (north of Point tolerate warm temperatures and/or low oxy- Conception, California) and P. o. segnis gen levels (Feder 1980). (south of Point Conception) (Clark 1996), Tidal Level: Intertidal to 88 meters (Feder but morphological evidence and genetic 1980). Large sea stars usually found at low homogeneity across populations of suppo- tide mark in Puget Sound, Washington sed subspecies and morphological forms (probably for warmth), but they do not move (e.g. “forma” Fisher 1930; Harley et al. to the lower intertidal in Monterey, California 2006) supports the single species P. (Feder 1970). ochraceus (Stickle et al. 1992; Lambert Associates: Mussels, barnacles, limpets and 2000; Frontana-Uribe et al. 2008; see also other snails. Other inhabitants of the mussel http://echinoblog.blogspot.com/search/ bed include polychaetes, anemones and nem- label/Pisaster%20ochraceus). atodes. On pilings in quiet waters, associates include barnacles, anemones (e.g. Metridium Ecological Information senile) and tunicates (Ricketts and Calvin Range: Type locality is near Willapa Bay, 1971). The parasitic ciliate Orchitophrya ste- Washington (Ahearn 1995). Range includes llarum causes castration in males (Leighton et Sitka, Alaska south to Baja, Mexico (Ricketts al. 1991). Several incidences of sudden sea and Calvin 1971). Reported subspecies star die off have occurred since 1972, but the with differing distribution include P. o. most recent to the northwest coast of North ochraceus, occurring north of Point Concep- America began in June 2013 and is called sea

star wasting disease. Affected individuals California Feder 1956, 1980) with peak have ectodermal lesions and tissue decay spawning from May–June (San Juan Islands, that eventually leads to death (within 2–3 Washington, Chia et al. 1987; Miller 2001). days). The water-vascular system loses the Eggs of P. ochraceus are pale orange and ability to maintain hydrostatic pressure and 150–160 µm in diameter and a 400 g female individuals often look flaccid when infected. can produce up to 40 million eggs (Menge Increased temperature further heightens in- 1975). The gametogenic cycle of both sexes fection intensity (Bates et al. 2009). The is regulated by photoperiod (Chia et al. 1987). current die off of sea stars is the most signifi- At 12˚C, development proceeds as follows: 2 cant due to its widespread geographic range cells at 5hr, 4 cells at 6hr, 8 cells at 7hr, and large number of species infected hatching at 29–32 hr, gastrula at 44–63 hr, (Hewson et al. 2014). Recently, researchers planktotrophic bipinnaria larva at 5d post determined this disease is most likely asso- fertilization (Chia et al. 1987). ciated with a family of single stranded DNA Larva: Embryos develop into planktotrophic viruses (densovirus, Parvoviridae) and is larvae called bipinnariae (Chia et al. 1987; now called sea star-associated densovirus Miller 2001). These larvae are approximately (SSaDV). Incidentally, this same virus was 400 µm in length and metamorphose into ju- detected in museum specimens and, thus, venile sea stars after 76–228 days when they may have been present on the Pacific coast are 0.5 mm in length. Bipinnaria larvae are and undetected since those specimens were easily recognizable in the plankton (Fig. 26.1, collected in 1942. Although the specific pa- 26.2, Chia et al. 1987), they are large, fleshy thogen is not known in certainty, SSaDV is and uniformly ciliated with a distinct, continu- currently the most likely candidate (Hewson ous ciliated band that is used for feeding and et al. 2014). swimming. Larvae have a large mouth, Abundance: The most conspicuous sea esophagus, intestine and anus. They can star of rocky intertidal areas (Puget Sound, have many long arms, increasing in number Washington, Kozloff 1993; Mah 2007). with age and can become long and floppy (Fig. 3, Miller 2001). The juvenile sea star de- Life-History Information velops from the left posterior portion of the Reproduction: Forcipulate asteroids primar- larval body. Late stage bipinnaria develop ily have separate sexes and free-swimming three arms (called brachiolar arms) and a planktonic larvae (Fisher 1930; Chia et al. central adhesive disc, anteriorly. Larvae at 1987). Pisaster species do not brood their this stage are called brachiolaria (see Fig. 4, eggs or young as do some Asteriidae (e.g. Miller 2001) and they use these arms to at- Leptastarias, Mah 2007). Many species can tach to the substratum at metamorphosis. be induced to spawn and are routinely used Juvenile: Sexual maturity is reached at five in developmental research. One pair of gon- years when individuals are 70–95 g (wet ads is present in each arm and, when weight) (Menge 1975). spawning, sea stars lift their body supported Longevity: by their arms and gametes are released Growth Rate: Varies with food availability through gonopores on the aboral surface and microhabitat (e.g. wave exposure). With (Chia et al. 1987). Ten gonads, like feathery constant food supply and proper conditions, a tufts, two in each ray, occur next to the cen- sea star can feed continuously and increase tral disc in P. ochraceus. The spawning its weight from 2–30 times in a year (Feder period is from March to June (Monterey, 1970). It can survive at least 20 months with-

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