Five or more arms. At least one adambulacral is fused into an adoral carina. The adambulacrals are wider than their length. Crossed and straight pedicellariae are present, the former usually in dense tufts around the spines. The aboral skeleton is meshlike. The tube feet are arranged in four rows.
Click on the image below to view an expanded illustration for this taxon. If more than one illustration is available for a species (e.g., two subspecies may be illustrated) then links to the separate images will be provided below.
Pisaster brevispinus is a large stiff-armed, pinkish-grey sea star usually found on soft substrates. It has five arms up to 32 cm long and an arm-to-disc ratio of 2.8 to 5.0. The aboral surface is a meshwork of plates with smallish spines standing alone or in clusters, with crossed and furcate pedicellariae in wreaths around the spines or standing on their own. Abundant grey or light purple papulae occur between the spines, interspersed with large lanceolate pedicellariae. The superomarginal spines are larger than the aboral spines and are separated from the inferomarginals by an obvious channel. Two or three stout inferomarginal spines have clusters of crossed and furcate pedicellariae on their distal sides. Two series of oral intermediates with stout spines also have clusters of pedicellariae on their distal sides. The adambulacrals bear a single slender spine with a tuft of pedicellariae on the plate near the base of the spine. Twelve to fifteen adambulacral plates form a long adoral carina, with mouth plates at the proximal end usually sunken and obscured by tube feet.
Characteristics
Similar Species
No other five-armed sea star in this region (the area from Glacier Bay to Puget Sound to a depth to 200 metres) can match Pisaster brevispinus for size and bulk. Its smaller relative P. ochraceus is never pinkish-grey and is usually foun
Pisaster brevispinus captures bivalves by elongating the tube feet near the mouth to penetrate the substrate and grasp prey, such as the Butter Clam (Saxidomus giganteus), Little Neck Clam (Protothaca staminea), Geoduck (Panope generosa) and Ribbed Clam (Humilaria kennerleyi). P. brevispinus attacks rock boring clams by inserting its tube feet, drawing the clam towards the mouth and applying its stomach. In winter, 70 per cent of observed P. brevispinus were feeding, with 70 per cent of these on barnacles and the rest on Geoducks and Jackknife Clams (Solen sicarius). In California, P. brevispinus feeds on the Horse Clam (Tresus capax) and the Eccentric Sand Dollar (Dendraster excentricus) which tries to escape by burying itself in the sand. In Puget Sound, however, P. brevispinus shows little preference for sand dollars. On rocky substrates it eats the Giant Barnacle (Balanus nubilus). The Olive Snail (Olivella biplicata) exhibits a strong escape response when approached by P. brevispinus.
Fisher describes P. brevispinus as one of the largest known sea stars. It breeds from April to August. Divers have seen it spawning in August with its central disc humped up and gametes streaming from paired gonopores. In December, nutrient stores in the gonad increase and the nutrients in the pyloric caeca diminish.
Sitka, Alaska, to Santa Barbara, California, from the intertidal zone to 128 metres deep. Common in shallow waters on mud, sand or broken shell. Smaller individuals also occur on rocky substrates.
