Appearance: Sponges vary in shape depending on where they live. Most in the rocky intertidal are encrusting. They are soft and range in color from yellow to purple to red to green.

Ecology: Sponges may look like simple plants, but many are surprised to find out that they are animals. They are relatively simple, but can grow in all shapes and sizes depending on where they live. Sponges growing in calm water tend to have more tube and volcano like structures. In the intertidal however they will often grow very flat due to high surf action. Sponges use many tiny holes called ostia to suck in sea water and shoot it out larger volcano openings called oscula. While the water is within the sponge it filters out all of the tiny organic particles, like bacteria, to feed and other nutrients needed for growth. That would be like humans surviving off of air alone! Look closely and you may find some well matched nudibranchs living and feeding on the various intertidal sponges.

(surf anemone, clonal anemone)

Anthopleura elegantissima

Size: up to 3” in diameter.

Habitat: Found in colonies on rocks in the low to mid intertidal. Colonies prefer to settle in depressions or crevices of rocks, but can multiply to cover entire rock surfaces.

Appearance: Aggregating anemones are attached to rocks by a pale green to gray colum. They often attach sand, small pebbles and bits of shell to their body exterior using adhesive papillae cells (verrucae) located on the column. The mouth is ringed with pink or purple tentacles which surround a broad oral disk.

Behavior: Aggregating anemones have the ability to reproduce asexually by dividing into two identical individuals. Colonies, therefore, are genetic clones. Upon close inspection, one may notice that colonies are typically separated by a narrow anemone-free path. This is because when genetically distinct individuals come into contact with one another they recognize that they are from different colonies and a violent battle ensues. Using nematocyst-laden tentacles that are club-shaped, neighboring colonies repeatedly beat and sting each other until they declare a truce and leave a border between colonies.

Anthopleura xanthogrammica

Size: Up to 12” in diameter and 12” tall.

Habitat: Found in tidepools and rocky shores, as well as at depths of 50’ or more.

Appearance: Dark olive-brown column with bright green oral disk and tentacles.

Ecology: These large, seemingly solitary animals actually have a very close knit, mutualistic relationship with green algae which gives them their color. The algae live inside the anemone consuming carbon dioxide and nitrogenous waste given off by the animal. In return, the algae give organic compounds to the anemone for its growth.

Epiactis prolifera

Size: Up to 4” tall and 2” in diameter at the disk.

Habitat: Intertidal and shallow subtidal.

Appearance: Come in a variety of colors including pink, green, brown and orange, with characteristic white markings at the bases of the tentacles. The oral disk and column have radiating white stripes.

Ecology: Eggs of mature females are fertilized by planktonic sperm in her digestive cavity. Once the embryos develop into free-swimming larvae they escape through the oral disk and settle on the parents column where they live for about 3 months. As they develop into juvenile anemones they crawl away from the parent. If you look closely, you can see the developing juveniles with your naked eye. This is even more spectacular looking through a hand lens!

Appearance: It’s impossible to find two limpets that look identical. Their variety in colors and patterns make searching for them an adventure with something new on each rock. Look for a shingle cone shaped shell with either a hole at the top (key hole limpet) or ones without (true limpets).

Ecology: Limpets rely on their powerful suction power to protect them from predators pounding waves. In fact they can grip harder onto their rock with every pound of a wave. They often have a home scar where they can both grip and hold in more water at low tide. These simple creatures have the ability to sense when an enemy, usually a sea star, is around. When the situation arises, they can glide away with their shell hiked up like a big southern bell skirt. The alternative is to just let go of the rock and fall out of harms way. Most limpets are vegetarians and graze on thin layers of algae that grow on rocks. Their sandpaper-like tongue, called a radula, extends to the rocks and conveys the broken up food particles into their mouth. Most limpets have a designated home territory where it cruises around during high tide. When the water recedes, some species even nestle into a “home-scar”, which over time they have carved into the rock.

Cryptochiton stelleri

Size: Growing up to 13” in length, this organism is the largest chiton found in the world.

Lifespan: Up to 25 years.

Habitat: Found in protected rocky areas of the lower intertidal.

Appearance: This organism looks like a wandering meatloaf, but don’t be mistaken! The eight calcareous plates, characteristic of all chitons, lay hidden beneath a thick, leathery covering. The red-brown girdle contrasts with the yellow-orange foot and gills of the underside.

Ecology: While other chiton species are nearly impossible to remove from rocks, the Gumboot can be easily picked up to observe the underside. The majority of the bright yellow underside is the chiton’s foot used for locomotion. Lighter colored fibrous parts around the edges of the underside are the chiton’s gills. Look carefully and you may see a worm that lives in the chiton gills. If you choose to pick up one of these creatures be sure to put it back exactly where it was found.

Tegula funebralis Appearance: Up to 1 1/4” in diameter. Their shell is thick and black to purple in color often with a white cap on the cap of the shell (the oldest part).

Ecology: Looking for snails in the tidepools can sometimes be tricky. Don’t be surprised if you pick one up and it’s actually a crab! Hermit crabs are notorious for using black turban snails’ old shell as their home. Snails are part of the “belly-foot” family, meaning that they eat, move, and stick to rocks with their strong, fleshy body. Most snails are vegetarians and feed on algae or seaweeds using a specialized mouth part called a radula. The black turban snail is prolific in the mid to high intertidal and can be found in large groups under rocks and in crevices. The white circle on the top of the shells is actually the oldest part of the snail. It can live to be more than 20 years old! Sometimes you will see sponges, limpets or smaller snails on the backs of black turban snails as well.

Olivella biplicata

Appearance: Up to 1 1/2” long smooth shell, white to purple to olive green in color.

Habitat: These snails can be found living an inch or so underneath the wet sand. Look for irregular patterns on the sand, dig with your fingers and you will most likely discover a purple olive snail! Their shells are also used for hermit crab homes.

Ecology: Miwok Indian tribes of the northern California coast and Chumash Indian tribes of southern California’s channel islands used these beautiful shells as money for trade and decorations on clothing and jewelry. Imagine begin able to go out and collect dollar bills on the beach! If you look closely on the shell you will see very fine lines showing the pattern of growth. The oldest part of the snail is at the very top of the spiral. The snail puts on tiny layers each year as it grows more and more. Sometimes people ask how old many of the creatures of the tide pools are. This is a rather difficult question to answer, but we can get some sense by looking at the number of lines on the purple olive snail. Some snails you pick up will have varying patterns. Some of the lines are very straight while others are very jagged. The jagged lines may indicate a rough point in the snail’s life where maybe they were attacked or lived through a rough winter. The smooth lines indicate an easy year for the snail. By reading the lines we get a story of this snails long-lived life experiences.

There are many species of nudibranch. Some of the most locally common to see are: the opalescent (Hermissenda/Phidiana crassicornis), the sea lemon (Anisodoris nobilis), the leopard (Dialula sandiegensis), and the red nudibranch (Rostanga pulchra).

Size: This highly diverse class of organism ranges from a fraction of an inch to a foot in length.

Habitat: Often found on rocks, kelp, mud, and sponges of the intertidal and subtidal zones. Some species are pelagic.

Diet: Nudibranchs are carnivores that feed on sessile animals such as hydroids, sea anemones, soft corals, bryozoans, sponges, ascidians, barnacles and fish eggs.

Appearance: Nudibranchs have various shapes, colors and patterns. The most locally common types are the dorid nudibranchs and the aeolid nudibranchs. Dorids have a flattened body shape, paired sensory projections on the head, and often a retractable gill plume at their back end. Aeolids are distinguishable from the dorids by the often colorful and flashy cereta (gills that are tentacle-like in appearance) protruding from their backs.

Ecology: Some aeolid nudibranchs ingest the specialized stinging cells of cnidarians, passing them through their digestive tract both intact and unfired. The nudibranch then transfers these stolen stinging cells from branches of its digestive tract into its cerata (gills) and uses them for its own defense. Some pelagic species are even known to ingest and retain the stinging power of the Portuguese Man of War!

If while observing a nudibranch, you also notice close by a fleshy material attached to a substrate in an intricate pattern you are possibly the lucky observer of a nudibranch egg mass. A nudibranch has a gonopore on one side of its body from which it secretes a mucus-like membrane filled with thousands of egg capsules. It lays the egg mass by traveling in a circle with the gonopore facing inward. This way the animal avoids walking over its own egg mass, and the eggs are kept in a tight spiral.

Mytilus californicanus

Appearance: Up to 10”long, these bivalves have two thick blue to black shells. Often the ribs of the shell wear off with age. They live in large groups in the mid rocky intertidal while boat dock mussels can get much larger. They have bright orange bodies protected inside of their shell.

Ecology: You will most likely find mussels living in large clumps. Where a young mussel chooses to settle will determine the length of its life. Too high and it will die from dehydration, too low and it will get eaten. Most choose a place that already has adults present. Often you can see a strong zonation of mussels on any rocky shore. Other animals like barnacles and sponges will often be living on mussels. Once a young mussel has found the right spot, it attaches itself with strings made of protein called byssus. These byssal threads are elastic bands secreted by a gland that provide it with limited movement. They are also what allow us to wiggle them like a loose tooth. When the tide comes in the animal replenishes itself with oxygen rich water while it collects plankton for its meal. It does this by siphoning water and pulling it over its gills, which collect oxygen and food simultaneously.

Pollicipes polymerus

Size: 1”-2” tall.

Habitat: Living on rocks in the intertidal zone.

Diet: Filters small crustaceans and other planktonic species from the water.

Appearance: This animal is connected to the rock by a dark, rubbery, stalk. Atop the stalk are white shell plates.

Ecology: This barnacle is commonly found living with the black mussels (Mytilus californianus) is the rocky intertidal. They are found in tightly packed clusters. The stalk of the animal contains reproductive organs and the cement gland that keeps the animal attached to the surface of rocks. The rest of the animal is in the upper part behind the shell plates. To feed the shell plates open up and long, feathery appendages extend out into the water to catch food.

Size: Most inhabit shells that are one inch tall or smaller.

Habitat: All parts of the rocky intertidal, usually underwater or under rocks at low tide.

Diet: Hermit crabs feed primarily on algae, but will eat other plant and animal material.

Appearance: The crabs have no hard covering to their bodies so they protect themselves by living in the shells of other mollusks. If the crab is inactive all this will be seen is the shell. When active the crabs head, antennae, pincers, and walking legs will extend out of the shell. As the crab grows it needs to find a larger shell. This is why it is important to leave empty shells in the intertidal and not collect them to take home.

Ecology: Hermit crabs can provide great amusement. Some species are so skittish that simply passing by their tidepool causes them to pull back into their shell. This sudden retraction and loss of footing often sends the crab and shell tumbling down to the bottom of the pool. Try picking up a shell and patiently waiting as the crab will slowly emerge and begin walking accross the palm of your hand.

Pycnopodia helianthoides

Size: Around 2’ in diameter.

Lifespan: 3-5 years.

Habitat: Found in the rocky intertidal.

Appearance: These large radially symmetrical sea stars come in a variety of colors including, purple, purple-gray, red-orange, and orange. Adult sunflower stars have 15- 24 arms, which, like all seastars, they can regenerate when lost. Some explorers of the tidepools mistake these sea stars for an octopus because of their large, soft, and flexible body. On close inspection you may notice that their bodies are covered in small calcareous spines. The underside has thousands of transparent-yellow tube feet, which are used for suctioning, walking across surfaces and feeding.

Ecology: A top predator in the tidepools, Pycnopodia helianthoides has the ability to eat a wide variety of organisms including, crabs, chitons, sea urchins, abalone, turban snails, and other sea stars. Its large size, as well as its ability to move 1 meter/minute, allow it to quickly and easily overtake its prey.

The escape responses of many intertidal invertebrates to a close by sunflower star are quite exciting to observe. For example, a sea urchin will walk away, flatten its spines and stick out its bright white pinchers in the presence of a sunflower star. Another example is with the cockle. In this relationship a chemical cue from the sunflower star causes the cockle to dramatically protrude its foot. The foot is almost twice the size of its shell and is very quickly shot out. The cockle will use foot to push itself away.

Strongylocentrotus purpuratus

Size: 1” – 4” in diameter .

Lifespan: Up to 50 years.

Habitat: Lives intertidally down to 525’ deep from southern Alaska to Mexico. Found frequently in kelp forests and on algae covered rocks. They erode the rocks they live on forming depressions over time. Urchins create these pits using their spines often leaving their spines blunt. The pits serve as excellent protection for the animal, but they give a bit of freedom. Once in a pit they are there their whole lives. Pits are made larger and deeper by many generations of urchins.

Appearance: Covered in purple calcareous spines that protrude out of a dome-shaped shell (test). When observed in water you may notice long extended tube feet as well as tulip-shaped pinchers (pedicellariae) that lie between the spines. Purple urchins are often found decorated with pieces of shell, rock, or algae from their environment, which stick to their tube feet. This decoration helps to protect them from UV light, desiccation, and predators. Sea urchins are a quite curious and scary looking animal to many people exploring the tide pools. Often, individuals are afraid to touch them for fear that their spines are sharp and venomous. Although some tropical species have these characteristics, spines of Oregon’s common purple sea urchin (S. purpuratus) and red urchin (S. franciscanus) do not contain venom and generally aren’t sharp enough to puncture the skin, if handled carefully. Often, a purple urchin has blunted spines from living in constraining depressions in the rocks. Diet: Purple urchins are mainly grazers of macro algae, meaning they eat seaweed. To do this they use their Aristotle’s lantern, an intricate jaw composed of nearly 81 parts including 5 teeth that meet in the middle.

Ecology: The sunflower sea star is a purple urchin’s main predator. Birds such as oystercatchers and gulls can also be seen to feed on accessible urchins. A study done in Washington estimated that oystercatchers could take up to ½ of the purple urchin population present in an intertidal zone. This has major ecological effects including an indirect increase in algal cover, and an increase in the diversity of algae. Another prime predator for purple urchins is the sea otter. However, this only occurs where sea otters are, which doesn’t include the Oregon coast. In addition, along the U.S. Pacific coast, red, purple and green sea urchins are commercially harvested. Harvesting takes place at depths of 5 to 100 feet where sea urchins are harvested from the ocean bottom with a hand-held rake or hook. In Oregon, sea urchin harvesting developed when southern California catches declined in 1986. Port Orford, Coos Bay and Gold Beach are the main landing.

Haematopus bachmani

Size: 8” in height.

Habitat: A non-migratory, rocky-shore bird.

Appearance: A large shorebird with black plumage, pink legs, and red-rimmed yellow eyes. Its long, thin, bright orange bill is used to catch prey from crevices, mussel beds and rocks. It has a characteristic high-pitched piercing call, which can often be heard above the noise of the surf.

Ecology: Oystercatchers forage at low tides on a variety of intertidal animals, but especially on mussels and limpets. As a mussel gapes open when splashed by a rising tide, they are vulnerable to oystercatcher predation. The bird must deliver a quick, sharp stab between the two shells and sever the adductor muscles so that the mussel doesn’t close down on the oystercatcher’s beak. Once inside, the oystercatcher will withdraw the meat and swallow, yum! With limpets, a true treat, oystercatchers will jab at the edge of the shell in order to dislodge the limpet from a rock. The oystercatcher will then shake out the meat and swallow it in one gulp. Look for empty limpet shells that have a nick out of their edge. This is a sign they have been eaten by an oystercatcher.