Friends of Netarts Bay Watershed, Estuary, Beach, and Sea

Saxidomus gigantea
Butter Clam
Alaska to California
Family Veneridae
Native

The Butter Clam (Saxidomus gigantea), also known as the Smooth Washington Clam, Martha Washington, and Quahog, is probably the favorite from Netarts Bay. This clam has thick, oval shells, sculptured with fine concentric ridges, that are chalky-white except when stained black with ferrous sulfide, present in sediments with little oxygen. It has an external hinge ligament, and the shells are often slightly gaped, showing a wavy, frilly-looking mantle fold. It lives about a foot deep in sandy sediments and can be dug easily at low tide with a shovel. If the tide flat is exposed, look for a depression or hole in the sand about half an inch across. You can stick your finger about an inch into this hole before you find it plugged with sediment. This is the spot where the clam extends its neck (siphons) for breathing and feeding when the tide is in. A good digging area is out from the kiosk at he public clamming area toward the end of the sandbar. Butter clams are considered the best chowder clams. They have a large foot, two large adductor muscles, and a meaty neck. The whole clam can be eaten, but some people like to clean out some of the gonad, digestive gland, and the crystalline style, the gelatinous worm-looking organ. It is also wise to clip off and discard the black ends of the siphons because they can accumulate biotoxins.

External hinge.

Wavy mantle fold.

Sponsored by the Friends of Netarts Bay Watershed, Estuary, Beach and Sea (WEBS)

Clinocardium nuttallii
Nuttall's Cockle
Alaska to California
Family Cardiidae
Native

Nuttall's Cockle, because of its short neck, lives under just a few known as the heart cockle, basket cockle, and cockle clam, its species is named after Thomas Nuttall (1786-1859), an English biologist who spent a large part of his career exploring the America, including the Pacific Northwest, and whose name is associated with several clams. Its thick, rounded shells, up to four inches across and colored yellowish tan with brown or reddish accents, radiate 34 to 38 distinct ribs, crossed by fine growth rings. A strong burrower with a powerful, muscular foot, it can escape its major predator in the bay, the many-rayed sunflower star Pycnopodia helianthoides, by using its foot to almost leap away. Nuttall's cockle can live up to 16 years. Though tasty, it has a strong flavor and is mainly used in chowder and fettuccine. To open and shuck cockles easily, blanch them first in boiling water for about 20 seconds. You can find cockles in the sand and mud shallows on the east side of the bay.

Tresus nuttallii
Pacific Gaper Clam
Alaska to Mexico
Family Mactridae
Native

Tresus capax
Fat Gaper Clam
Alaska to California
Family Mactridae
Native

The Pacific Gaper Clam (Tresus nuttallii) is the largest and deepest burrowing clam in the bay. Also called the horse clam and the blue (a local name), it can reach eight inches long and burrow down to three or more feet. Its shell, when not stained, is creamy white and partly covered with a brown varnish-like chitinoid coating called a periostracum. The two shells gape on the posterior end where the neck protrudes, hence its common name. The clam can also be identified by the internal hinge ligament that fits into a pair of spoon-shaped depressions in the shells called chondrophores. The large neck, the meatiest part of the clam, has fused incurrent and excurent siphons and is sheathed with part of the periostracum. The tip of the neck bears two hard, leathery plates. These gaper clams are found in various parts of the bay, usually clustered in sandy sediments, although there is a cobble area just south of Happy Camp that has a good population. The neck hole is an inch or more across, and if you stick in your finger, you can feel the hard plates just before the siphons is retracted. You may also get hit with a jet of water that is expelled when the clam is disturbed. When digging for the clam, be careful not to break the fragile shells. The neck, after tenderizing, is good fried or in chowder, but should be dipped in boiling water first to aid in removing the outer tough skin. The leathery plates can be clipped off. When cleaning the clam, you will likely find one of three species of commensal (or parasitic) pea crabs, Pinnixa faba, Pinnixa littoralis, or Fabia subquadrata in the mantle cavity. They also inhabit other clams.

Another gaper clam, the Fat Gaper (Tresus capax), with a rounder more robust shell, also occurs in the bay, but is not as common. The tip of its siphon does not have the hard, leathery plates. Its shells, probably from offshore populations, are commonly washed up on the beaches outside the bay.

Tresus nuttallii

Tresus capax

Mya arenarea
Softshell Clam
Alaska to California
Family Myidae
Non-native

The Softshell Clam (Mya arenarea) is a naturalized import from the east coast, possibly introduced in 1869 with shipments of oysters to San Francisco. It is found in scattered groupings in intertidal sand and muddy areas about four to twelve inches below the surface. It may be up to four inches long with a chalky-white, brittle shell that has a periostracum around its margins. Its left valve or shell (the posterior of the clam has the neck) has a distinct internal protuberance, the chondrophore (arrow), which sticks out from the hinge. Softshell clams do well in low saline waters, so they may be prevalent where creeks flow into the bay. To feed and breath, the clam passes water in and out of its mantle cavity through two tubes, called siphons, that protrude from the hind end of the shell. In Mya arenaria these siphons are tan or brown and are fused together into a single, thick "neck" that is oval in cross-section. Mya arenaria lives buried up to 30 cm below the surface in sand, mud and clays, often in mixtures with coarse gravel, when disturbed, it quickly withdraws its siphon into its burrow, emitting a jet of water. When withdrawn into the shell the siphons sit in a kind of pouch formed by an infolding of the clam's outermost tissue. A curving line on the interior of the shell, called the pallial line, shows where this tissue attached to the shell; an indentation in the pallial line, which reaches to the middle of the shell in Mya arenaria, traces the outline of the pouch. Because of their fragile shells, they are easily broken when dug. Softshell clams are an east coast favorite, steamed, fried, and in chowder. Nearly all those in Netarts Bay contain pea crabs which makes them not quite as delectable.

Chondrophore

Leukoma staminea
Pacific Little Neck Clam
Alaska to Mexico
Family Veneridae
Native

The Pacific Little Neck Clam (Leukoma staminea; formerly Protothaca staminea) is the narrow radiating ribs and concentric growth ridges. This is a fast growing and fairly long living clam, sometimes reaching as 16 years. Its growth rate tends to slow with age. It has a short neck with fused siphons and burrows from one to ten inches into sandy, muddy, and sometimes gravely sediments. It, like some of the other clams, is found in patches and is not very common. It is often dug with a shovel, but shallow populations can be raked out using a tree- or four-pronged rake. Better yet, I usually wear soft watershoes or go barefoot so I can feel them with my feet. I then just reach down and pick them up. That method does not disturb surrounding plants and animals. Small, two to three-year-old clams are best for steaming. They are typically eaten whole.

You may occasionally find the Japanese Littleneck or Manila Clam (Venerupis phillppinarum), which resembles the Pacific Littleneck but is more oval and has colored streaks on its shell, about four inches deep in sandy to gravely sediments. It was introduced from Japan to the West Coast in the 1930s.

Solen sicarius
Sickle Jackknife Clam
Alaska to Mexico
Family Solenidae
Native

You can occasionally find the Sickle Jackknife Clam, which resembles a skinny razor clam, nestled in the eel grass beds of Netarts Bay, buried up to a foot and a half deep in the silt where it prefers a sheltered habitat. It is four to five inches long, has a dark brown periostracum, and a pearly white inner shell. Its hinge is near the anterior end. It is an aggressive digger with its muscular foot and can move freely up and down its permanent burrow when disturbed. It is edible but is not abundant.

Olive snail.
At low tide across some sand flats in Netarts Bay you may encounter meandering and crisscrossing trails of the beautiful little purple olive snail.
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Nuttallia obscurata
Dark Mahogany Clam
British Columbia to Oregon
Family Psammobiidae
Non-native

A recent arrival to Netarts Bay is the Dark Mahogany Clam (Nuttallia obscurata). Also called the Purple Varnish Clam, it is native to Japan, Korea, and possibly China. It entered British Columbia around 1992 in ballast water, rapidly spread southward, and took up residence in Netarts Bay probably after 2000. It is now common in most Oregon estuaries. It has flat, oval shells, slightly elongated on the rear end, a prominent ligament, and can be most easily recognized by its shiny dark brown periostracum that makes the clam look like it’s been painted with spar varnish. The inside of the shell is a vivid purple. It has no single neck; siphons are separate, and it is both a suspension and deposit feeder. There is a dense concentration of these clams on Netarts Spit, directly across the bay from the boat launch, high up in the intertidal zone. You do not need a very low tide for harvesting. Look for small siphon holes close together. They bury in sand about six to ten inches deep. Wear gloves if you dig them with your hands. The edges of the shells are sharp. They are excellent steamed or seasoned and grilled on the halfshell. The digestive gland is a dark green and, if you don't want to eat it, can be removed with a flick of the thumb you clean the clam.

Macoma sp.
Macoma Clams
Alaska to California and Mexico
Family Tellinidae
Native

Macoma Clams come in several species in the bay. All have separated incurrent and excurrent siphons and are predominantly deposit feeders, vacuuming up detritus with the incurrent siphon from the surface of the sediment. Rexithaerus (Macoma) secta (the former subgenus Rexithaerus has been raised to genus level), the White Sand Macoma, up to four inches long, is the largest. Its thin shells, marked by shallow concentric growth rings, have no radial ridges except a posterior crease on each valve that runs from the umbo to the shell margin. The hinge is external and short. It is found buried at least eight inches deep. Macoma nasuta, the Bent-Nose Macoma, is small, not much more than a couple of inches long, but is the most distinctive Macoma because its valves are bent to the right at the posterior end and its siphons are orange. It is common in Netarts Bay and can live in sediments that range from clean sand to those that are very muddy, anaerobic, and noxious. Macoma inquinata, the Pointed Macoma, is similar in size but without the bent shells and its siphons are yellowish. Limecola (Macoma) balthica, the Baltic Macoma, is little more than a half inch long and fairly round. All the Macomas, if large enough, are edible and make good steamers.

Rexithaerus (Macoma) secta

Macoma nasuta

Relative sizes: left M. nasuta, right R. secta

Peronidia (Tellina) bodegensis
Bodega Tellin
Alaska to Mexico
Family Tellinidae
Native

Netarts Bay has a number of clams in the family Tellinidae, at least one Peronidia (the former subgenus Peronidia has been raised to genus level) and several species of Macoma. We also have a recent arrival from Asia, Nuttallia obscurata, carried here in ballast water, which is in the same super family Tellinoidea (see above). All members of this super family are deposit feeders. Unlike most clams which are suspension feeders and draw in material suspended in the overlying water, deposit feeders use their inhalent siphon, which is separated from the exhalent siphon, to vacuum up food sitting on the bottom. Tellina bodegensis is an elongated, ivory white, clam with a fine commarginal lined sculpture. It's about two inches long and prefers clean sand near the north end of the bay or along the open beach.

Siliqua patula
Pacific Razor Clam
Alaska to California
Family Pharidae
Native

Pacific Razor Clams are not common along out local beaches, but they probably more abundant in deeper waters off Netarts and Oceanside judging from the numbers of shells washed ashore, but currently few are shallow enough for digging Many of these shells have their periostracum intact, not worn by the surf, indicating that they come from nearby populations. According to a 1958 educational bulletin by the Fish Commission of Oregon, clams were common at the north end of Netarts Bay near the entrance, and local Jim Mundell (the founder of WEBS) dug razor clams in Netarts Bay and at Oceanside when he was a kid. I occasionally find them there myself at the end of Netarts spit, but for now, you will need to find other razor clam beaches such as Seaside. There are a few on the Cape Meares beach.

The Pacific Razor Clam is a fast burrower in moist sand. Its powerful foot clears a vertical path, pushing away sand then anchoring itself to pull the clam downward, so that within seconds it can bury itself. It does not have a permanent borrow. It lives in long, flat, but energetic, wave-swept beaches where the sand is continually shifting. Sexes are separate, and they broadcast spawn. In our area, they live 10 to 12 years, 19-20 years in Alaska, but only 9 years at the southern end their range in California.

The x-ray-looking image of the "transparent" razor clam was sent to me by Dr. John DeMartini, Humboldt State University, and shows many of the interior organs, including the labial palps (labpal), anterior and posterior adductor muscles (ant & post), crystalline style (crystyl), digestive gland and stomach (diglstom) and intestine (int), gills, incurrent and excurrent siphons (incsiph & excsiph), and the mantle (mant).

There is an odd-looking commensal nemertian (Malacobdella siliqua) worm that often attaches with a sucker to the base of the incurrent siphon or to the gills in razor clams and feeds on plankton that passes over the gill surface. Many people have inadvertently eaten this worm along with the clam.

Razor clams. in my opinion, are the tastiest of our local clams, and they bring a high price in restaurants. However, in the last few years harvesting has been frequently closed along the Oregon coast because of high accumulations of domoic acid, a neurotoxin that causes Amnesic Shellfish Poisoning (ASP) and is secreted by a type of phytoplankton that the clams feed on. So, before you go clam digging, check with the Oregon Department of Agriculture by calling the Shellfish Hotline.

Crystalline style (1.5 in, 4 cm long) of an adult clam

Zirfaea pilbryi
Rough Piddock
Alaska to Mexico
Family Pholadidae
Native

The Rough Piddock (Zirfaea pilbryi), a Pholad, burrows into shale, clay, or firm mud. The anterior half of the shell is covered with concentric ridges of “teeth” used for rasping its way into these hard substrates. It has a large siphon, too big to be withdrawn into the shell; its surface is covered with chitinous tubercles. The clam ranges from Siberia to Baja California. This is a big clam, sometime more than a foot long. It is often mistaken for the Pacific Geoduck (Panopea abrupta), family Hiatellidae, which may have been found in Netarts Bay in the past but is no longer be here. The rough piddock can be dug just off the village of Netarts and probably occurs in other parts of the bay where there are clay outcrops. There is a lot of meat on this clam that can be pounded into steaks and fried or made into chowder. It is not my favorite tasting clam.

Hiatella arctica
Arctic Nestler
Alaska to Chile
Family Hiatellidae
Native

Hiatella arctica is called a nestler because it will use vacant burrows left by other boring clams, such as pholads, that have perished. The Arctic Nestler is easily recognized by its fused red-tipped siphons. It varies in shape, sometimes elongated, sometimes stubby, and can grow up to an inch and a half (4 cm) long. Whether it become a nestler or a burrower depends on the type of substrate. If it is soft, a juvenile will settle and burrow using both chemical and mechanical means to penetrate the rock. If it is hard it will attach with byssal threads to algae holdfasts and other substrates. Boring clams do not develop a byssus. It is found in both intertidal and subtidal zones. It is a suspension feeder.

Pennitella penita
Flat-tipped Piddock
Alaska to Mexico
Family Pholadidae
Native

Another Pholad, the common Flat-tipped Piddock, is small, three inches or less, and drills into fairly soft sedimentary rock such as siltstone and shale. The boring is strictly mechanical, using the rasp-like teeth on the anterior end of the shells. To assist the rasping, the clam extends its foot, which is flat on the end and can stick to the rock like a suction cup and form an anchor point as it grinds away at the surface by rotating its shells back and forth. The teeth that are worn away are replaced as the shell grows. At some point, when the clam matures, the drilling stops. Then the foot withdraws, and the anterior ends of the shells are joined by a calcium deposit and sealed. The burrow at this point is large at the bottom to accommodate the clam's anterior end and tapered toward the top, leaving a small hole through which the Piddock can extend its fused siphons. The common name of the clam comes from the two leathery flaps at the posterior end.

Crassadoma gigantia
Giant Rock Scallop
Alaska to Mexico
Family Pectinidae
Native

The Giant Rock Scallop lives along our rocky, wave-swept shore in the low intertidal and subtidal zones. Free-swimming when young, it attaches to rocky substrates where it can grow up to ten inches in diameter and live for fifty years. Its bivalve shell is thick and robust, radially ribbed on the dorsal valve, purple on the inside around the internal hinge, and the two valves are held together by a single massive adductor muscle. Posterior “wings”, shell extensions, are present in young individuals but may be absent in older scallops. The mantle is adorned with many black eyes. Sexes are separate, although young males may become females. It is a phytoplankton filter feeder and is preyed upon by Ochre Stars and humans who harvest the yummy adductor muscle. The Giant Rock Scallop is plentiful along the base of Three-Arch Rocks and along the base of the rip-rap at the north end of Netarts Bay.

The shells may be infested with a boring sponge Cliona californiana. This yellow sponge, when young, will bore small holes (1-2 mm) into calcareous substrates such as limestone and shells, particularly in the shells of rock scallops and red abalone. The holes may eventually penetrate the shells, weaken it, and kill the mollusk host. When older, the sponge can form large patches on rocky surfaces.

Portion of sponge-riddled shell.

Pododesmus macrochisma
Green False-Jingle, Rock Jingle
Alaska to Mexico
Family Anomidae
Native

This unusual bivalve, common on the rip rack rocks along the eastern edge of Netarts bay, has a pear-shaped hole in the in the right valve near the hinge through which a byssus cements the bivalve to any hard substrate, giving it the appearance of a very flat round limpet. The shells are thin, often green on the inside because of algae living within the shell, but otherwise with a pearly polish. The left valve, which faces upward and is slightly domed, has a large muscle scar on the inside. Its outer surface is slightly ribbed, and the valve shapes itself to the form of the substrate to which it is attached. It may grow to four inches (10 cm) across. The flesh inside is bright orange. It may be eaten by predatory gastropods and sea stars.

Left valve

Right valve

Neaeromya rugifera
Mud Shrimp Clam
Alaska to Mexicio
Family Galeommatoidea
Native

This commensal clam can be found attached by its byssal threads to the underside of the Mud Shrimp, Upogebia. Strangely, it is also commensal to and entirely different host, the Sea Mouse polychaete, Aphrodita, which I don’t believe has been found in Netarts Bay. These clams associated with the two hosts are genetically the same but do have different morphologies. That on the underside of the Mud Shrimp is indented on its ventral side; that associated with the Sea Mouse is rounded.

The one found on Mud Shrimp have thin shells and needs the protection of the shrimp’s burrow to avoid predators. Since the shrimp provides a constant flow of water through the burrow, the clam can easily breathe and feed even though it lacks siphons. Little seems to be written on it general biology. It is known to be a protandrous hermaphrodite, meaning it is both male and female but produces eggs and sperm at different times.

The genus name is both from Greek, referring to a girl mentioned in the writings of Horace (Neaero), and Latin referring to a sea-mussel (mya). The specific name means bearing wrinkles.

Mytilus californianus
California Mussel
Alaska to Mexico
Family Mytilidae
Native

The California Mussel is one of the most obvious and first noticed animals in the rocky tide pools along Tunnel Beach. It dominates much of the mid-intertidal zone, if not in numbers, certainly in biomass. It can grow to eight or more inches (20+ cm) long. It resides in dense “mussel beds” on the wave-swept rocks from Maxwell Point to Cape Meares, often associated in mature beds with the goose-neck barnacle Pollicepes polymerus and the thatched barnacle Semibalanus cariosus, creating what is called a “mussel-barnacle assemblage”, which can also harbor other invertebrates that find protection within the beds. Mussels attach to a substrate by means of tough threads, the byssal threads, which are secreted by the byssus gland at the base of the foot. The thread is first secreted as a proteinaceous liquid which flows along a byssal groove along the back edge of the foot where it is molded into a thread. The thread then attaches to the substrate, cementing itself as a small disk. The thread quickly hardens, and the foot is withdrawn. Many threads are secreted to both the rocky substrate and to neighboring mussels creating a network that can withstand the heaviest of pounding seas.

The California Mussel, and other mussels, are suspension feeders, sucking in food-laden water through the inhalant siphon by the action of lateral cilia on the gill lamellae that create a current to bring water into the inhalant chamber and through the gills. Other cilia capture food, entangle it in mucus, and transport it to food grooves that run longitudinally along the edge of the gill where it is pre-sorted from non-food. Final sorting is done at organs called labial palps before the food enters the mouth. Non-food particles are ejected through the exhalent siphon by means of periodic contractions of the adductor muscles.

The main predator of the California Mussel is the Ochre Star Pisastor ochraceus.

Mytilus trossulus
Bay Mussel, Pacific Blue Mussel
Alaska to Mexico
Family Mytilidae
Native

The Bay Mussel resembles the California Mussel but has no radial ribs along its shell. It has long been misidentified as Mytilus edulis, a North Atlantic species, but DNA studies have confirmed its identity as M. trossulus. However, it may hybridize with M. edulis from west coast mericulture of M. edulis and with M. galloprovinciallis, a European mussel introduced to the West Coast. Bay Mussels prefer quiet waters with lower salinity than ocean water, and are the mussels often served in restaurants along with the introduced species as "steamed mussels." M. trossulus are scattered various locations midway up Netarts Bay. It is a filter feeder, capturing food on its gills which is then transported to the mouth. During time of red tide, it can accumulate toxins that can result in PSP, paralytic shellfish poisoning. It has many predators, including seastars, crabs, drilling snails, some fish, birds, and mammals.

Modiolus rectus
Straight Horsemussel
British Columbia to Peru
Family Mytilidae
Native

The Straight Horsemussel is a large brownish mussel, up to nine inches long, that lives in sandy to muddy sediments. It is usually solitary, but Kozloff reports it in clusters in Puget Sound. It may attach to hard substrates with byssal threads, although this specimen was found unattached and solitary, buried in mud at the southern end of the bay. The shell may bear periostracle hairs, especially in young individuals, as are seen in the left side of the photo. The umbo is set back from the anterior end and the shell is about three times as long as wide. Like other mussels, it is a filter feeder. Young are freely preyed upon, but as they age the shell becomes robust enough to discourage predators.

Nucella lamellosa
Wrinkled Dogwinkle
Alaska to California
Family Muricidae
Native

Inside Netarts Bay along the riprap on the eastern shore, especially near the boat ramp, resides the Wrinkled Dogwinle, a predator snail that is highly variable in shape, size, texture, color, and ornamentation, and can be difficult to identify. It feeds on barnacles (mostly the thatched barnacle Semibalanus cariosus) and mussels. This snail has an extendable proboscis at the end of which is a rasp-like radula that can scrape holes through the shells of its prey. The rasping is also aided by the accessory boring organ ABO) that secretes shell-dissolving chemicals. Once a hole is drilled, the snail inserts its proboscis, injects digestive enzymes, and sucks out the digested contents.

Mating may occur in spring and spawning in summer when the female deposits egg capsules in clusters that resemble yellow rice grains. Small snails emerge after 60 to 90 days.

N. lamellose radula - Scanning electron microscope image by Carrie Tyler, Miami University, and James Schiffbauer, University of Missouri)

Nucella canaliculata
Channelled Dogwinkle
Alaska to California
Family Muricidae
Native

The shell of Nucella canaliculata has deeply channeled spiral cords running around the shell. It is common in the mid-intertidal rocky areas of Tunnel Beach. Its shell is rough, not highly polished, and its colors may vary, as they do is some other Dogwinkles, from gray and brownish to orange in younger specimens. They are predators, feeding mostly on barnacles, especially Semibalanus cariosus, and young mussels by drilling holes in the prey’s shell with a radula. Different species of Nucella have different heat tolerances and therefore live at different tidal levels and at different latitudinal ranges. Nucella canaliculata, for example, prefers a slightly lower tidal level and extends farther north than N. osterina.

Nucella ostrina and Nucella emarginata
Northern Stripped Dogwinkle
Alaska to Mexico
Family Muricidae
Native

Some references list this snail as a single species, N. ostrina, with N. emarginata a former name. Others claim two distinct species. The World Register of Marine Species (WORMS), the authority of scientific names, lists them as distinct species. There is evidence that N. emarginata, a more southern species, genetically diversified over millennia as it moved northward to the point that two distinct species developed. Accordingly, our resident snail may be N. ostrina (see web reference below). Then again, we may have both. At any rate, they are a highly variable looking snails, ranging in colors from white to black, and with different surface textures on the shell.

They live on rocks between the high and low intertidal zones, and are roving predators, hunting down barnacles, limpets, mussels, and periwinkles, and drilling holes through their shells with a toothed radula. Once the prey's shell is perforated, the snail injects digestive enzymes, then sucks out the contents with its proboscis.

Sexes are separate in both species, and the female lays clusters of yellow to cream-colored capsules that are attached to a rocky surface, each containing hundreds of eggs. Most of the eggs in a capsule are “nurse eggs”, infertile and used as food by hatched embryos from fertile eggs.

WHELK: NUCELLA EMARGINATA VS. N. OSTERINA

Nucella ostrina

Nucella emarginata

Ilyanassa obsoleta
Eastern Mud Snail, Black Dog Whelk
British Columbia to California
Family Nassariidae
Non-Native

Imported from the Atlantic coast, the Eastern Mud Snail is abundant in mud flats and eelgrass beds, including those of Netarts Bay. It was formerly called Nassarius obsoletus but differs from others in the genus because it does not have the basal groove in the shell, caudal cerri, and bifurcated foot typical of others in the family. It also has a crystalline style, uncommon in gastropods. It feeds on oysters and mussels and is considered a pest. It is also a deposit feeder and scavenger. You may find its round egg clusters attached to rocks, sticks and eelgrass blades.

Neverita lewisii
Lewis’s Moonsnail
Alaska to Mexico
Family Naticidae
Native

Formerly in called Polinices lewisii, Lunatia lewisii and Euspira lewisii, Lewis’s Moonsnail is the largest gastropod in Netarts Bay, growing its shell to almost six inches. It has a large, expandable foot (12 inches or more) for pushing through the sand and a chalky-white shell, often covered with algae. You will find it at low tide on the sand flats where it is a clam predator, feeding on littlenecks, gaper clams, soft-shell clams, and especially the butter clam. It will wrap its foot around a clam and then use its robust radula, a tongue-like organ with chitinous teeth, to drill a hole in the clam shell, often near the umbo, the hinged top of the clam. Specialized glands secrete enzymes and even hydrochloric acid to aid the drilling by softening and dissolving the shell. Once the clam shell is drilled, the moon snail will spend several days sucking out the clam's meaty contents. You can distinguish a hole drilled by a moonsnail from the holes of other gastropod predators by its sloped sides. When disturbed, the moonsnail will retract its foot into its shell and close off the entrance with a large operculum.

It lays eggs in a large coiled gelatinous “egg collar” that contains both eggs and sand. Eggs hatch into veliger larva. Females are larger than males and can live to more than fifteen years.

Egg collar

Shell of clam drilled by N. lewisii

Tegula (= Chlorostoma) funebralis
Black Turban Snail
Vancouver Island to Mexico
Family Trochidae
Native

This snail is very abundant in the rocky intertidal on the south side of Cape Lookout and can also be found in Netarts Bay at low tide in the rocky area near the Netarts Bay RV park and Marina.

The Black Turban Snail is easy to recognize with its blue-black, matt finished shell, often brownish at the top, and coiled like a turban that may grow to an inch or more in diameter. The interior of the shell is a pearly white. It has a brownish round operculum, textured with many spiral lines, to close off the opening when the foot is retracted. Its foot is long and narrow with four tentacles on each side. The outside of the foot is black.

It inhabits the exposed rocky coast from high intertidal to low intertidal but is most common in the mid-intertidal levels. Wave exposed areas have higher numbers of large individuals; protected areas have higher numbers of juveniles. It is a grazer, scraping almost any fleshy algae with its radula. Sexes are separate and can be determined by the color of the sole of the foot, males light, females dark. They may reproduce most of the year, especially in southern populations, but in Oregon there is some seasonality.

Their main predator is Pisastor ochraceus, the Ochre star.

Olivella (=Callianax) biplicata
Purple Olive
Alaska to Mexico
Family Olividae
Native

At low tide across some sand flats in Netarts Bay, you may encounter meandering and crisscrossing trails of the beautiful little purple olive snail Olivella biplicata. The snail creates “tracks” as it plows through the sand hunting food (lower photo). Its polished shell forms gentle whorls colored purple, gray, and tan. Sometimes you can find this delicate animal on top of the sand, especially at night. Other times you may have to dig an inch or so underneath its trails or into the small mound of sand at a trail's end. If you turn Olivella so its aperture is upward, you may see its muscular foot extend and wave around as it tries to right itself.

Olivella can also be found on the open beach at low tide. Look for a small mound of sand, often with a trail leading to it. The snail is buried just underneath.

The purple olive snail ranges from Sitka Alaska to Baja California. It reproduces by laying egg capsules that hatch into free-swimming veliger larvae. Sea stars, shorebirds and moon snails are important predators. It is probably omnivorous.

The Chumash Indians of Southern California, especially the Channel Islands, used purple olive shells as beads and money (Chumash literally means "bead money makers"). They may have been use as tender or jewelry by Native Americans for thousands of years. Olivella biplicata shells were found at the Marmes Rock Shelter along the Washington’s Snake River in deposits dated as far back as 7600 to 9000 years.

The Purple Olive has long been in the genus Olivella. The family Olividae is mostly tropical, and Olivella biplicata is a northern temperate snail. It has been proposed that subgenus Callianax be raised to genus level because of differences in morphology from its tropical relatives in the genus Olivella. However, to date (2018), the World Register of Marine Organisms (WORMS), the authority on scientific names of marine organisms, still lists Olivella biplicata as the accepted name.

Littorina scutulata
Checkered Periwinkle
Alaska to Mexico
Family Littorinidae
Native

The small Checkered Periwinkle lives high up in the splash zone, often among the Ribbed Limpets Lottia digitallis. Rarely more than a centimeter long and often not checkered, but rather a dark drab brown, green, or black, you can find it clinging to the rocks of the open coast, such as Tunnel Beach, and on the riprap at the County boat ramp in the more protected Netarts Bay. Its shell may often be encrusted with algae or eroded. It is herbivorous with a radula for scraping algae. It has an operculum, a brownish trap door, that can close off the aperture and prevent water loss when the snail retracts into its shell. When gliding along the surface of a rock, it will secrete a mucous film that helps attach its foot to the substrate which also helps prevent water loss. It respires with gills that only need to be wetted occasionally by the spray of waves, enabling it to live out of water for weeks or months. Sexes are separate, fertilization is internal, and broadcast spawning is in late spring and summer. It begins with a planktonic trochophore larva followed by a veliger larva that settle in three to four weeks. They feed on both microscopic and macroscopic algae.

Checkered

Not checkered

Littorina keenae
Eroded Periwinkle
Oregon to Mexico
Family Littorinidae
Native

Another periwinkle, Littorina keenae the Eroded Periwinkle, crawls around the same splash zone rocks as L. scutulata, with similar behaviors, though in smaller numbers. It is larger, up to two centimeters (0.75 inches) and can be recognized by two distinct features: a white strip within the base of the aperture and spiral grooves at near the top of the inner lip of the aperture. Both littorines feed in the same way eating the same food. Each has a horny operculum, a door, to close off the aperture and conserve water. The shell of L. keenae is often rough and eroded, hence its common name.

White stripe and spiral grooves.

Alia gausapata
Dove Snail
Alaska to Mexico
Family Columbellidae
Native

Also called Astyris gausapata (before that Mitella gausapata and Mitrella gouldi), this is a small snail common in Netarts Bay’s eel grass beds. You can find it by dragging a net over the bottom. It could also be Alia carinata which also occurs in eel grass beds, though Kosloff (1983) says that this species has a distinct ridge running around the top of the body whorl, a “shoulder” (juveniles do not have this ridge, and considerable variability exist in adults). According to the Washington State Department of Ecology an identifying characteristic for A. gausapata are axial striations on the columella, as shown in the photograph of our specimen. Whichever species we have, the one we found were no more than three eighths of an inch (10mm) long crawling along the bottom.

Millimeter scale

Axial striations

Lottia digitalis
The Ribbed Limpet
Alaska to Mexico
Family Lottiidae
Native

The Ribbed Limpet is the most common limpet in the upper rocky intertidal areas of the outer coast. It is in the subclass of gastropods called the Patellogastropoda, the “true” limpets (See Diodora aspera). The oldest individuals are found highest up into the splash zone, sometimes higher than any other marine animal. You can recognize this limpet by the pronounced ridges on the shell. It is somewhat of a homer, that is it has a preferred spot on a rock that it returns to after foraging. It will move higher onto the rocks during winter when waves are higher to avoid being dislodged. It feeds on micro algae, diatoms, and newly settled barnacles by scraping the food off the rock surface with a tongue-like organ called a radula coated with rasp-like chitinous teeth (see image). The dark color of the teeth is due to the biomineralization of iron incorporated into the teeth. To avoid desiccation, the limpet secretes a mucous seal between its shell and the rock. Sexes are separate, and it reproduces by broadcast spawning

Ribbed shell

Ventral side with foot, mouth, and tentacles.

Radula

Lottia pelta (probably)
Shield Limpet
Alaska to Mexico
Family Lottiidae
Native

The Shield Limpet can be recognized by its brown ribless shell, sometimes with blotchy light spots, a tall apex that is slightly anterior, a dark rim on the interior of the shell, and a creamy white to brown interior with a dark apex. There may be a lighter ring just below the apex as illustrated in this photo. There is a lot of color and pattern variability and the shell may be eroded, often by boring sponges, as shown in the third image. It lives on lower intertidal rocky surfaces and is common on the rocks of Tunnel Beach at low tide and is found in mussel beds. It is in the subclass of gastropods called the Patellogastropoda, the “true” limpets (See Diodora aspera).

Shell eroded by boring sponges

Lottia persona
The Mask Limpet
Alaska to Mexico
Family Lottiidae
Native

This rather large, somewhat flat limpet can be found along the bottom of the riprap on the east side of Netarts Bay, clinging tightly to the rocks among the many thatched barnacles and sometimes with another limpet Lottia scutum. Its apex is off center, shifted forward and concaved on the anterior side. It is slightly ribbed, though the ribbing can be eroded. The surface of the shell is variably speckled; on some the speckling is obvious in ray-like patterns, on others its slight. Backlighted with a strong light shows that the anterior markings are translucent, which enables the animal to gauge ambient light (see image). The interior of the shell has a light bluish region bordered by a dark margin and dark apical stain. It is intertidal and lives in sheltered waters, often under rocks. It is active nocturnally.

Translucent markings on anterior end of shell

Lottia scutum
The Pacific Plate Limpet
Alaska to California
Family Lottiidae
Native

This limpet, along with Lottia persona, can be found on the riprap rocks in the sheltered waters of Netarts Bay. It has an oval, flat shell, its apex slightly anterior, with dark and light spots and lines that radiate outward toward the shell’s edge. These marking may be obscured by growth on the top of the shell but are obvious along the inside edges if the limpet is detached from the rock. It is in the subclass of gastropods called the Patellogastropoda, the “true” limpets (See Diodora aspera). It lives mostly in mid to lower intertidal. It feeds on microscopic and encrusting red algae, using its radula, a tongue-like structure with chitinous teeth to scrape away food material. Growth rates have been found to be related to food availability and are subsequently seasonal, growing fastest in late spring and summer and slowest in winter. Those in the lower intertidal areas grow faster than those higher up.

Compare the radula of L. scutum with that if L. digitalis. The shapes and patterns of radula teeth are species specific.

Radula

Acmaea mitra
The Whitecap Limpet or Dunce Cap Limpet
Alaska to Mexico
Family Acmaeidae
Native

This is a true limpet that is pure white with a high profile, making it one of the tallest limpets for its diameter. It shell is almost conical, the apex just slightly anterior. It lives on the rocky open coast in low intertidal and subtidal zones where it feeds on the encrusting coralline algae Lithothamnion and Lithophylum. Its shell is often covered with of these algae, turning its surface a bumpy pink. You can find its surf-worn shells washed up on the beach.

Cranopsis multistriata
Many-Ribbed Puncturella
Alaska to Mexico
Family Fissurellidae
Native

Previously in the genus Puncturella, this gastropod (gastro=stomach, pod=foot) is a member of the subclass Vetigastropod, which are the most primitive gastropods, many of which have a slit or hole in the shell. The shell of this limpet has about thirty primary ribs separated by one to three secondary ribs. A hole just anterior to the apex is elongated instead of round. It is herbivorous, using a radula, a rasping tongue-like organ to scrape algae off rocks and other hard surfaces. Males and females are broadcast spawners, shedding their eggs and sperm into the water. Embryos first develop into a free-swimming trochophore larva and later into a veliger which will metamorphose and settle as a juvenile. It inhabits the low intertidal and subtidal zones. I have not found this limpet live, but shells are often found on the beach.

Diodora aspera
Rough Keyhole Limpet
Alaska to Central America
Family Fissurellidae
Native

This is a large limpet, two-and-a-half inches or so long, with round hole, the anal opening, on the anterior side of the shell apex. This is a member of the subclass Vetigastropod, which are the most primitive gastropods, many of which have a slit or hole in the shell. Found on rocks in the low intertidal or subtidal zones, it is a grazer that prefers to eat encrusting bryozoans. A clean shell shows dark stripes radiating out from the apex, but live animals can be overgrown with other organisms, masking the design. It is preyed upon by sea stars, but can sometimes be protected by a commensal polychaete, the scale worm Arctonoe vitata that lives in the mantle cavity and will bite the sea stars tube feet.

Aeolidia papilosa
Shaggy Mouse Nudibranch
Alaska to Mexico, circumborial
Family Aeolidiidae
Native

Nudibranchs are in the Subclass Heterobranchia* under the Class Gastropoda.
One of the most common nudibranchs in the world, it occurs in both intertidal and subtidal zones, down to about 3000 feet. Along our coast, you can find it in tide pools where it feeds on the sea anemones Anthopleura xanthogramica in wave-swept habitats and Metridium senile in protected waters. It spreads a mucus on the column of the anemone, possibly to protect itself from the anemones nematocysts (stinging cells), then scrapes off chucks of flesh which it then swallows. The mouth is protected by a cuticle that resist nematocysts. It also ingests cells that have undischarged nematocysts and moves them through the digestive ceca (the hepatic diverticula), which extend into the dorsal cerata (gills), to the cerata tips where these recycled nematocysts are use for defense. These cerata line two sides of the dorsum (upper side) and are flattened and lanceolate, giving the appearance of a shag rug. As with other aeolid nudibranchs, its anus is on its right side.

*The former subclass Opisthobranchia is no longer valid.

Cadlina luteomarginata
Yellow-Rimmed Nudibranch
Alaska to Mexico
Family Cadlinidae
Native

The Yellow-Rimed Nudibranch pictured here was collected around the riprap near the boat ramp in Netarts Bay. It is typically found in the lower intertidal and subtidal zones, usually around rocks. You can identify this dorid nudibranch by its yellow margin and its yellow-tipped papillae, the small bumps on the dorsal surface. The two projections on the anterior end are rhinphores, chemosensory organs. Like other some other dorids, it is also a sponge eater, feeding on a variety of encrusting species, including Halichondria, Myxilla, and Higginsia, by rasping with its radula. It can extract certain chemicals, called terpenoides, from sponges that are deposited in their skin and may serve as a defense against predation. However, it is eaten by sea stars.

The yellow-Rimmed Nudibranch can be distinguished from the similar looking Acanthodoris hudsoni by its short yellow-tipped papillae. The papillae of the latter are long and hair-like.

Doris montereyensis
Monterey Sea Lemon
Alaska to California
Family Dorididae
Native

Doris montereyensis is a sea slug (a Nudibranch). Formerly of the genus Archidoris, it is lemon yellow, with rough skin on it dorsal side, with dark spots between and on its tubercles, a rosette of yellow gills on the posterior half of the dorsa side, and two projecting horn-like rhinophores that are chemosensory organs. It is sponge eater, feeding mostly on the yellow to olive-green Halichondria. In our area, we find it in the lower intertidal region along the rocky outer coast because that is where its food is. Typically, it grows to two to three inches long but can exceed six inches. Hermaphroditic, it reproduces throughout the year. Fertilized eggs, when laid, are arranged in capsules that are strung together and folded into a wavy gelatinous ribbon that attaches by one edge to a hard substrate. The sea lemon is a member of the Dorid nudibranchs, those that breath through a flower-like array of gills on the posterior end of their dorsal side.

Dirona albolineata
Frosted Nudibranch, White-Lined Dirona
Alaska to California
Family Dironidae
Native

Ranging in color from pink and purplish, to yellow as pictured here, to pure white, this delicate and picturesque nudibranch is a favorite with divers and nudibranchophiles. It can be so translucent the you can see it internal organs. Its flattened cerata have a white margin along with its frontal veil, the flap that overhangs the mouth and foot. It can be found intertidally to depths of more than one hundred feet, usually on rocks but sometimes on mud. It feeds on bryozoans, small crustaceans, hydroids, mollusks, and ascidians. It can grow to six inches long. Its cerata may be infested with a parasitic copepod, Ismaila. When stressed, it may shed its cerata as a diversion, then grow new ones later.

Hermissenda crassicornis
Opalescent Nudibranch, Horned Aeloid
Alaska to Mexico
Family Facelinidae
Native

Probably our most colorful nudibranch, this intertidal beauty is a member of the super famliy Aeolidiodea, commonly called the Aeolid (=Eolid) nudibranchs, which are characterized by having no shell and multiple rows of dorsal projections called cerata. These cerata function in both respiration and defense. These sea slugs eat mostly hydroids and sea anemones which are armed with stinging cells called nematocysts. They feed using both blade-like jaws and a radula, a tongue-like structure coated with rasping teeth. As they feed on the hydroids, they hijack the nematocysts and incorporate them into their cerata as a confiscated defense system. Their bright colors may ward off potential predators. Hermissendas also go into aggressive battle with each other. When two meet they may joust and bite, the winner usually eating the loser. They may grow to three inches long, but only live less than a year. They are hermaphrodites that cross fertilize. Eggs are laid, usually onto seaweed or eel grass, in a coiled ribbon that looks like a miniature mass of top ramen.

Triopha modesta
Clown Nudibranch
Alaska to Mexico
Family Polyceratidae
Native

The Clown Nudibranch is one of the most distinctive along our coast with its white, translucent body decorated with bright orange-tipped papillae, gills, and chemosensory rhinophores. It is a favorite of divers and tide poolers. Common on rocky shores, it is often found sub-tidally on kelp. It feeds on foliose bryozoans. It is hermaphroditic, but does not self fertilize. It can grow up to six inches long but is usually two to three inches.

Triopha catalinae and T. modesta were formerly lumped together as T. catalinae. Now separate species, the papillae on the former are small bumpy knobs. On T. modesta, they are frilly (Thanks to Greg Jensen, University of Washington for pointing out the difference).

Acanthodoris nanaimoensis
Nanaimo Dorid
Alaska to California
Family Onchidorididae
Native

This dorid nudibranch is generally characterized by brown-to-red-tipped rhinophores, though the colors may vary, and yellow-tipped conical papillae on the dorsal surface giving it a furry appearance. The base color of the body is often white but may be gray in older individuals. The gills have nine branched plumes with colored tips. It is found in rocky intertidal and subtidal areas and may grow to an inch and a half (4 cm) long. It feed on bryozoans and compound ascidians. The name comes from the city Nanaimo, British Columbia, Canada.

Phyllaplysia taylori
Zebra Leafslug or Eelgrass Sea Hare
British Columbia to Mexico
Family Notarachidae
Native

Phyllaplysia is not a nudibranch, in that it lacks exposed gills. Instead the gills are tucked under flaps that run along the dorsal side of the animal. It also has a small internal shell on its dorsal side. It is found exclusively on the native eelgrass Zostera marina where it feeds on epiphytes and diatoms. It green color and stripes make excellent camouflage. It has no free larval stage, but hatches juveniles. This specimen was found in Netarts Bay eel grass in April.

Rostanga pulchra
The Red Dorid
Alaska to Argentina
Family Discodorididae
Native

The Red Dorid is small, growing to slightly over a half inch (1.5cm), and it lives on the red sponges, including Clathria pennata and Ophlitaspongia pennata. It has a retractable gill plume and a pair of rhinophores, and its dorsal side is covered with small tubercles and sometimes dark spots. There are outer papillae along the edge of its dorsum. The rhinophores each have a single vertical protuberance surrounded by fine, almost vertical lamellae. As with nearly all heterobranchs (the Subclass Heterobranchia*, which includes nudibranchs, is under the Class Gastropoda), R. pulchra is hermaphroditic. There is no self-fertilization, so two individuals cross fertilize, and eggs are laid in ring-like structures. The eggs hatch in 15 to 16 days into free-swimming veliger larvae which settle and metamorphose into juveniles 35 to 40 days. The vertical range of adults is lower intertidal to subtidal.

*The former subclass Opisthobranchia is no longer valid.

Photos are by Claudine Rehn

Janolus fuscus
White and Orange-tipped Nudibranch
Alaska to California
Family Proctonotidae
Native

Janolus fuscus (the species name is “dark” in Latin) is easy to recognize because its cerata have a white tip subtended by a yellow band. It has lamellate rhinophores and a comb like sensory appendage between the rhinophores. A digestive gland has an unbranched extension - the dark centers of the cerata - through the length of each ceras (sing. of cerata). The cerata may also swell when the animal is disturbed. The nudibranch feeds on foliose bryozoans. It frequently suffers infections of an endoparasitic copepod Ismaila belciki, especially here in Oregon where the infection may run may be 80%, which can render the nudibranch sterile.

Photo by Claudine Rehn

Diaulula odonoghuei
The Leopard Dorid, Spotted Dorid
Alaska to Mexico
Family Discodorididae
Native

The Leopard Dorid, formerly D. sandiegensis, is a pale gray to white but sometimes a pale yellow to dark brown depending on its diet, but the dark brown-black rings on its dorsal surface make it easy to recognize. It can be large, up to four inches (10 cm) long. It ranges from intertidal tidepools to deep subtidal and feeds mainly on sponges. Its dorsal surface is covered with minute tubercles giving it a velvety appearance. There are two anterior rhinophores and a posterior plume of tripinnate gills. It is hermaphroditic and may self-fertilize. It lays a circular ribbon of eggs.

Photo by Claudine Rehn

Corambe steinbergae
Steinberg's Corambe
Alaska to Mexico
Family Corambidae
Native

This small cryptic nudibranch lives solely on the encrusting bryozoan Membranipora on which it feeds. This specimen was found near the boat launch in Netarts Bay. Its dorsal side has white reticulations that help it blend in with the surface of the bryozoan. It may grow to 15 mm (a little more than a half inch) in length. It is usually found at low intertidal to subtidal habitats. There is a related species, Corambe pacifica, in the same range also living on Membraipora. It can be distinguished by a posterior notch.

Photos by Claudine Rehn

Corambe steinbergae

Corambe egg clusters on Membranipora

Katharina tunicata
Black Leather Chiton
Alaska to California
Family Mopaliidae
Native

The Black Leather Chiton is easy to find among the rocks in the mid to lower intertidal area of Tunnel Beach, just north of Oceanside. It is one of our larger chitons, averaging about three inches. Look for it among the rocky outcrops during spring and summer low tides.

It is a mollusk in the class Polyplacophora, all of which have eight dorsal shell plates (called valves), a marginal girdle, and a single muscular ventral foot. The shell plates of K. tunicata are almost covered with the mantle; only the central section is protruding. As with most chitons, it is an herbivore, using it tongue-like radula to rasp microalgae and macroalgae from rocks and other hard substrates. It is preyed upon by the Ocher Star.

Unlike gastropods with a single shell, the eight valves allow the chiton to flex and conform to irregular rocky surfaces, sealing the marginal girdle to the substrate reducing water loss. When dislodged from a rock, the chiton will curl itself like the terrestrial rollypolly isopod, probably a defense mechanism. Also, because of its flexibility, it can upright itself when turned over.

Looking at its underside, you will see the muscular orange foot, the marginal girdle, and the anterior mouth. If you peel back either edge of the foot to expose the mantle cavity, you will see an array of gills over which water flows from anterior to posterior to supply oxygen. The respiratory current is generated by rhythmic beating of gill cilia.

Tonicella lineata
Lined Chiton
Alaska to California
Family Tonicellidae
Native

Outside of the Gumboot Chiton Cryptochiton stelleri, the world’s largest chiton which I have yet to find here, this is my favorite chiton. Its eight plates are zigzag striped pink, orange, white, blue, brown and other color variations making it the most colorful of our local chitons. Its girdle is colored with alternating blocks of light and dark colors. It is a mollusk, in the class Polyplacophora (Greek for many plate bearer), that lives intertidally and subtidally on rocky outer coast, especially where there are coralline algae on which it feeds. They are eaten by ochre stars and six-rayed stars.

Mopalia hindsii
Hind’s Mopalia
Alaska to Mexico
Family Mopalidae
Native

Chitons belong to the class of mollusks called the Polyplacophora (poly=many, plac=plate, phore=movement). Polyplacophores have eight dorsal shell plates, also called valves, unlike gastropod mollusks which have single dorsal shell. These plates are surrounded by a fleshy mantle called a girdle that is usually adorned with spines, scales, or bristles, and it may partly or totally cover the plates. All chitons are marine. They have a single muscular foot that can grip rocky surfaces and hold them tightly to the substrate. Along each side of the foot is a row of gills, their shape and arrangement differing with species and sometimes used in identification. They have a mouth at the anterior end, and feed by grazing with a radula, a tongue-like organ with many chitinous teeth, that will rasp the surface of rocks to scrape off algae or other foods. Many mollusks have radulae adapted for carnivorous predation. The dark-colored teeth probably contain iron absorbed through a process called mineralization. New teeth continually replace those worn away by scraping. The shape and arrangement of teeth differ for different species and can be used in identification.

Mopalia hindsii is a common chiton in the mid-to-lower intertidal zones. It is omnivorous and will eat about anything in its path. It can be identified by a posterior cleft in the girdle and fine hairs on the girdle that are either unbranched or may have thin bristles at their bases. It may grow up to four inches long. Pictured here are surface and side views of its radula.

Mopalia muscosa
Mossy Chiton
Alaska to Mexico
Family Mopalidae
Native

Chitons belong to the class of mollusks called the Polyplacophora (poly=many, plac=plate, phore=movement). Polyplacophores have eight dorsal shell plates, also called valves, unlike gastropod mollusks which have single dorsal shell. These plates are surrounded by a fleshy mantle called a girdle that is usually adorned with spines, scales, or bristles, and it may partly or totally cover the plates. All chitons are marine. They have a single muscular foot that can grip rocky surfaces and hold them tightly to the substrate. Along each side of the foot is a row of gills, their shape and arrangement differing with species and sometimes used in identification. They have a mouth at the anterior end, and feed by grazing with a radula, a tongue-like organ with many chitinous teeth, that will rasp the surface of rocks to scrape off algae or other foods. Many mollusks have radulae adapted for carnivorous predation. The dark-colored teeth probably contain iron absorbed through a process called mineralization. New teeth continually replace those worn away by scraping. The shape and arrangement of teeth differ for different species and can be used in identification.

The Mossy Chitin Mopalia mucosa can be found in Netarts Bay in the rocky area next to Netarts Bay RV Park and Marinia. Just look on the underside of large rocks at low tide. It has a wide girdle covered with course bristles or “setae”, thicker and more robust than other species of Mopalia. It can grow to more than two inches (5 cm) long and does not have the posterior cleft in the girdle as does M. hindsii. It often carries barnacles attached to it plates.