Morning Sun Star

How to Distinguish from Similar Species: Pycnopodia helianthoides grows larger, has more rays, has pedicellariae, and has obvious ossicles projecting from the aboral surface. Solaster stimpsoni has an orange or pink aboral surface with a grayish-blue streak radiating from the central disk out along each ray.

Usually on rocky bottoms, but sometimes on gravel or sand

This large seastar has 8-16 rays and no pedicellariae. Paxillae on the aboral surface are separated from each other by about their diameter and blunt, so that the dorsal surface is rather smooth. The ambulacral grooves have enlarged marginal plates along their margins. Disk diameter is about 1/3 total diameter and the aboral surface does not have a prominent gray-blue streak radiating from the central disk and out each ray. Rays taper gradually from base to tip. Aboral surface usually brown or or grayish, but may be orange or mottled. Diameter to 40 cm.

Biology/Natural History: Solaster dawsoni is a predator on other seastars, including Solaster stimpsoni, other Solaster dawsoni, Leptasterias hexactis, Evasterias troschelii, Dermasterias imbricata, Henricia leviuscula, Crossaster papposus,Pycnopodia helianthoides, and Mediaster aequalis. It also has been seen to feed on the sea cucumbers Eupentacta quinquesemita, Psolus chitonoides, Cucumaria miniata, and young Parastichopus californicus, and on the nudibranch Tritonia festiva, which swims away rapidly when touched. Many other seastars also move away quickly when touched by S. dawsoni. S. dawsoni moves along with its leading rays raised, and lunges forward when it touches another star. S. stimpsoni, one of its favorite prey species, curls all its arms upward above the disk when encountered and sometimes wards off the attack. In Auke Bay, Alaska, S. dawsoni seems to eat mainly green urchins Strongylocentrotus droebachiensis. The commensal polychaete scaleworms Arctonoe vittata and Arctonoe fragilis are common on the star. Spawning occurs in mid April in southern British Columbia. Eggs are about 1 mm in diameter. Juveniles often take refuge among the tubedwelling polychaete Phyllochaetopterus prolifica.

Geographical Range: Point Franklin, Alaska to Monterey Bay, CA

Depth Range: Intertidal to 414 m