Sea Stars Of The Pacific North West


An amazingly rich assemblage of marine organisms lives in the cold Pacific Ocean along the shorelines of the Pacific Northwest. Of the thousands of plants and animals that dwell in these waters, sea stars are especially conspicuous. No matter the depth or the substrate, these echinoderms (echino-"spiny", derm-"skin") are among the most successful marine creatures inhabiting this rugged coast.
In his 1909 scientific paper, “Remarkable development of starfish on the northwest American coast”, naturalist A. E. Verrill noted: "No other part of the world, of similar extent, so far as known, has so many species of shallow water and littoral starfishes as the coasts of Alaska and British Columbia, including Puget Sound. The entire region has a very broken coast line, innumerable islands, bays, fjords and straits, giving a great extent of sheltered coast line, bathed in pure sea water and swept by strong tidal currents, all of which are very favorable to littoral marine life..."
Today we know that coral reefs of the tropical Indo-Pacific have even greater diversity of sea stars but compared to other temperate seas, the abundance and number of stars found along the west coast of North America is without equal in the world. In 1911, W.K. Fisher recorded 143 species from the shore to a depth of 4,100 m (13,450 ft) between San Diego, California and Point Barrow, Alaska, 70 of which are endemic (restricted to a specific geographical area) to the west coast. Recent studies in Alaska including the Aleutian Islands have reported more than 100 known species plus up to 25 newly discovered forms.
Sea stars roam the intertidal and subtidal zone, consuming every type of prey, including sponges, snails, clams, mussels, barnacles, sea cucumbers, tunicates, tubeworms, sea pens, anemones, gorgonian corals, scallops, fishes and even each other. Deceptively simple in appearance, sea stars are in fact superbly adapted, mobile creatures that have few natural enemies. They appear to be rather sedentary, inactive creatures, but they actually lead quite fascinating lives as they search for food and avoid predators.
Sea stars are members of the Phylum Echinodermata, invertebrate animals that have radial symmetry, calcareous skeletons and tube-feet. This group includes sea stars, brittle stars, sea urchins, sea cucumbers and feather stars. More than 6,000 species of echinoderms live from the intertidal zone to abyssal depths in all oceans of the world.