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Inhabitants of Oregon's Tidepools

Explore our interpretive guide to some of Oregon's most popular and common rocky intertidal plants and animals.

Also, learn about the communities (and zones) these species call home.

   

Common Name
Scientific name
Group

 Common Name Scientific name Group
Shaped overall like shallow bowls with ultra-thick bottoms attached to the substrate, sea anemones may look more like flowers than like animals—especially the ones that are green. Pointed “petals” around the top rim are stinger-armed tentacles that frame the central disc, the mouth of the animal. The floor of the central disc is smooth with a doughnut-shaped lump in the middle, while the outside of the body, below the tentacles, is usually a darker green and rough, and is often flecked with bits of shell. Most Oregon intertidal sea anemones are olive to bright green (some species have splashes of other colors). Depending on species, age, and environment, some of our tidepool sea anemones can grow up to 10” across.  

Giant green anemone

Anthopleura xanthogrammica

Cnidarian

 Giant green anemone Anthopleura xanthogrammica Cnidarian
Shaped overall like shallow bowls with ultra-thick bottoms attached to the substrate, sea anemones may look more like flowers than like animals. Aggregating anemones are small, often packed closely together with shell bits on the outside.  

Aggregating anemone

Anthopleura elegantissima

Cnidarian

 Aggregating anemone Anthopleura elegantissima Cnidarian
Slender, jointed legs and long, delicate antennae peek out (up to an inch) from beneath the edge of the stubby spiral of the black snail shell, along with short eyestalks and small-but-busy mouthparts. Undisturbed, hermit crabs jostle and jerk along the tidepool bottom and through the seaweeds: slow moving snail shells are probably actually snails, fast moving snail shells are probably hermit crabs inside old snail shells.  

Hermit crab

Pagurus spp.

Crustacean

 Hermit crab Pagurus spp. Crustacean
Shore crabs are compact and flat, with a nearly square back and legs that tuck tightly together and against the body. Our three species are generally dark and subtly patterned: fine, green stripes across the back from side to side; purple mottling on the back and spots on the claws; mottled greenish gray all over. Small (up to 2” wide) and very active, these crabs scuttle about when not hiding under rocks and in crevices.  

Shore crabs

Various species

Crustacean

 Shore crabs Various species Crustacean
Together acting like gently-cupped hands, dozens of off-white plates form two shielding halves around the bulk of the leaf barnacle’s body. A tough, brownish, rubbery stalk thicker than your thumb connects the leaf barnacle to the rock. Leaf barnacles tend to grow in clumps, and individuals in each clump tend to orient the same way.  

Gooseneck barnacle

Pollicipes polymerus

Crustacean

 Gooseneck barnacle Pollicipes polymerus Crustacean
From barely visible to larger than your fist, several kinds of barnacles are found in Oregon tidepools. Each hard white bump is generally volcano-shaped; the texture of the sides is somewhat different for different species, but is usually quite rough. In the recessed “crater” in the center are two tight-fitting shells that are the barnacle’s “doors.”  

Acorn barncle

Balanus glandula

Crustacean

 Acorn barncle Balanus glandula Crustacean
A classic “starfish” shape, ochre sea stars have five arms, each ending in a blunt point. Despite the name, ochre sea stars also come in purple to dark rose. All the back surface of an ochre sea star is covered with a loose net pattern of hard, light-colored bumps that protrude through a velvety surface; a small, light-colored bald spot is nearly always visible in the central back area. These sea stars can grow up to just over a foot wide.  

Ochre sea star

Pisaster ochraceus

Echinoderm

 Ochre sea star Pisaster ochraceus Echinoderm
Sea urchins are spheres, up to fist-sized, of richly purple spines. The spines are long enough to take up perhaps a quarter of the overall height and width of the urchin—about ½ to 1½ inches long, depending on the size of the urchin. Sometimes the urchin spines are tidy, arranged in neat rows radiating from the center top and down the sides to the bottom, other times the spines have pivoted about irregularly, giving the urchin a disheveled look. The softer tissues beneath and between the spines is very dark purple—nearly black. Some urchins have rocks or pieces of shells attached. Most purple urchins on the Oregon Coast live in shallow, urchin-shaped pits.  

Purple sea urchin

Strongylocentrotus purpuratus

Echinoderm

 Purple sea urchin Strongylocentrotus purpuratus Echinoderm
These turban snails are called “black” because their bodies are black: the shells are charcoal gray. A bit rough in texture, patches of the outside of the shell often erode to purplish and the top of the spire usually wears down to the white mother-of-pearl beneath. Rather squat, with a short spire of rounded whorls, black turban snails can grow to about 1½” high and wide.  

Black turban snail

Tegula funebralis

Mollusc

 Black turban snail Tegula funebralis Mollusc
Limpets are mollusks with one volcano-shaped shell; different species have different steepness to the slopes and different colors and textures. The ribbed limpet’s peak is noticeably forward of center, and low, bumpy ridges stretch from the peak to the edge of the shell. A wide muscular foot of each limpet fills most of the oval, open base of the “volcano,” with the rest of the animal inside.  

Ribbed limpet

Lottia digitalis

Mollusc

 Ribbed limpet Lottia digitalis Mollusc
Slick black oval lumps (up to 4½ inches long) with eight rough, somewhat diamond-shaped patches along the middle of the back, black-leather chitons clamp themselves firmly to the rock—firmly enough to withstand the heaviest surf.  

Black leather chiton

Katharina tunicata

Mollusc

 Black leather chiton Katharina tunicata Mollusc
Gumboot chitons are low-profile, saggy-loaf-shaped lumps that grow as long as a grown man’s foot. The entire back is covered by a pebbly/bumpy skin that is brownish-red. This pebbly/bumpy skin completely covers the eight over-lapping plates that form the back of the chiton; sometimes low bumps show where the plates are.  

Gumboot chiton

Cryptochiton stelleri

Mollusc

 Gumboot chiton Cryptochiton stelleri Mollusc
California mussels are bivalves (clam-like mollusks with two shells) that are about twice as long as wide, and nearly round in cross-section through the middle. These mussels have a blunt, rounded point at the bottom end, and are curved and somewhat flattened at the top end. Heavy, curved growth rings lay out from bottom to top of the shell, intersected by length-wise, radiating ridges; the hinge between the two shells is on one side, about a quarter of the way up from the bottom. Older, larger shells are heavy and tough. Overall, the shell is dark blue, but wears down on the raised parts (on some of the ridges and some places where the rings and ridges intersect) to a honey-tan, making the shell look vaguely plaid. Usually, the older part of the shell, at the blunt bottom, wears down to expose light blue under the surface and sometimes even exposes the white mother-of-pearl beneath. Occasionally, the blue-black edge of the animal can be seen between the shells.  

California mussel

Mytilus californianus

Mollusc

 California mussel Mytilus californianus Mollusc
Not surprisingly, our encrusting sponges are patches of slightly tough, spongy material that appears as if it were slathered on the rock and other hard surfaces, up to a quarter inch thick. The patches are irregular in shape and size, ranging from barely visible to areas larger than both your outstretched hands. Different species are different colors, with an astounding variety; different species vary in surface texture, too, from nearly-slick to rather tufted. There are tiny and larger pores in the spongy layer. In some species, such as the purple sponge in this photo, the larger pores are in the center of volcano- or nipple-shaped structures that protrude up to a quarter inch or more above the overall surface of the sponge. Some species are noted for the putrid smell they emit when crushed or rubbed.  

Sponges

Various species

Porifera

 Sponges Various species Porifera
Dusty-pink and brittle-looking, coralline algae look a lot like tufts of fine-scale coral. These seaweeds come in three different forms: flat fronds, jointed fingers, and bushy. Most coralline algae are smaller than your outstretched hand, but many of them can thickly carpet tidepools.  

Coralline algae

Various species

Seaweeds

 Coralline algae Various species Seaweeds
About as wide as your thumb, only flat, the “stems” that make up rockweed are forked and forked and forked again. The ends have a pair of blunt prongs and are often puffed or inflated. Little rockweed, a different species, is about a third the size of rockweed, with the “stems” being about pencil-wide and flat. Both olive brown, rockweed grows up to perhaps ten inches long, and little rockweed grows up to almost 4 inches long.  

Rockweed

Fucus and Pelvetiopsis

Seaweeds

 Rockweed Fucus and Pelvetiopsis Seaweeds
Smooth, ultra thin, and bright green, delicate sea lettuce covers the rocks in the upper intertidal. Two major shapes of sea lettuce are found on Oregon shores: broad (usually about the size of your palm or your whole hand) and narrow (usually about the size of your finger). Although sea lettuce starts out flat, it gently ruffles as it grows; older specimens often sport small holes and tears. Wet sea lettuce can look like limp cellophane cast about the beach—only much more slippery. Dry sea lettuce is pale green to dull brown and stiff, tightly papering the rocks.  

Sea lettuce

Ulva spp.

Seaweeds

 Sea lettuce Ulva spp. Seaweeds
True to their name, sea palms look like one- to two-foot tall palm trees, with a smooth “trunk” topped by a thick tuft of ridged “leaves,” each several to ten inches long, that loosely droop down, reaching a quarter to half the way to the rock. The upright stalk is held in place by a mass of curved and branching finger-like projections that hold fast to rock or mussels. The entire seaweed is olive brown.  

Sea palm

Postelsia palmaeformis

Seaweeds

 Sea palm Postelsia palmaeformis Seaweeds
These common fish are shaped like long, drawn-out teardrops, but with broad pectoral fins located just past the head. Rather triangular in cross section and with a long fin that runs down the back, tidepool sculpins rest on the bottom with their pectoral fins spread out on either side. The entire body is variously marked in browns, olive greens, and whites—often in saddles across the back. All of the several different species of tidepool sculpins are small, up to several inches long.  

Sculpins

Family Cottidae

Fish

 Sculpins Family Cottidae Fish
Somewhat larger than a pigeon and with long peach-colored legs, black oystercatchers are about 17” tall. Rather short-necked for a shorebird, these shorebirds are also unusual because their bodies are solid black. The red-orange bill is heavy and somewhat flattened side to side, adapted more for prying and stabbing than for probing fine sediment. Black oystercatchers have a distinctive call too, rather like high-pitched laughter.  

Other visitors

Various species

Various groups

 Other visitors Various species Various groups

 

 

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