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

Class Copepoda
Copepods
Worldwide

These ubiquitous “miniature” crustaceans live in all the world’s seas as well in freshwater lakes, streams, subterranean caves, forest leaf litter, polar ice, ocean trenches, and near hydrothermal vents. There are almost 13,000 described species with incredible numbers of individuals, making them the most numerous metazoans on the planet. Most are small, some less than a quarter of a millimeter (as is the one pictured here), though a few species may exceed a centimeter. Most are free living, but some are parasitic such as the salmon louse we find attached to locally caught salmon. In the sea, the near shore, and the estuary they are primary consumers and one of the most important food-web links from detritus and phytoplankton to larger organisms, which can range from juvenile fish to whales.

Unfortunately, given their ecological importance, the taxonomic literature for copepods of the Pacific Northwest is sparse, the nearshore and estuarine environments little studied. Therefore, I’m only introducing the free-living members of the class Copepoda in brief. There are three orders of marine free-living copepods: Calanoida, Harpacticoida, and Cyclopoida. The Calanoids are mostly planktonic and tend to have narrow abdomens and are slender. The Harpacticoids are mostly epibenthic (living just above or on the bottom) and have wider bodies with the front and rear parts nearer the same width. The Cyclopoids are both planktonic and epibenthic, and their body shapes depend on their habitat. There are males and females, and fertilization is internal. The eggs hatch as larvae called nauplii, of which there are six stages, followed by five stages of juvenile (copepodid) larvae before the final adult form. Copepods generally live from six months to a year.

Female copepod

Megalorchestia califoriana
California Beachhopper
British Columbia to California
Family Talitridae
Native

You will find them crawling or hopping along a sandy beach and sometimes nestled in washed up decaying eel grass or seaweed on which they feed and are protected there from predators such as shore birds. They are Megalorchestia californiana, the California Beachhopper, the highly mobile amphipod crustaceans that inhabit the wave-washed beaches between the Capes. Beachhoppers are collectively known as Talitrid amphipods because of the family in which they belong, and M. californiana can be easily recognized by its deep orange antennae. It lives mostly out of water up along the drift line of a fine sandy beach, its gills acting almost as lungs, entering the water only to wet the gill surfaces. It is mostly nocturnal, moving at night to the water’s edge where it scavenges for food.

It lives in burrows. Walking the beach, you can see excavated sand from the distinctive burrows that make elongated and crisscrossing patterns in the sand (pictured right). It digs head first by flicking sand grains with its legs up to ten or more inches (26 cm) from the hole. It will dig oriented in one direction for a few moments, and then it turns 180 degrees and flicks sand in the opposite direction for a few moments. It keeps repeating the 180 degree turns, piling up sand in two directions until it completes its burrow which can be more that a foot (30 cm) deep. Females are guarded in their burrows by males which will often battle with each other over females for the privilege of mating.

Exposed burrow

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

Grandidierella japonica
Japanese Invader
Japan, Pacific Coast of North America
Family Aoridae
Non-native

Grandidierella japonica is an invasive species from Japan that may compete with our native amphipods. It was first introduced in about 1928 from Hokkaido, Japan, possibly with the introduction of Crassostrea gigas, the Pacific Oyster, for cultivation on the American west coast, initially into San Francisco Bay. From there it spread north and south infecting bays and estuaries all along the Pacific coast. It has also been distributed via ballast water discharged from ships in ports around the world. It has now invaded Australia and Europe, including the Mediterranean Sea.

It is a mud dweller, building U-shaped tubes in the sediment out of detrital debris that house both male and female pairs. Females brood their young, so there is no free-living larval stage, and released young resemble small adults. It feeds on detritus and is eaten by fish. It is euryhaline, meaning it can exist in a variety of salinities. Sensitive to pollutants, it has been used in pollution bioassay tests to determine the toxicity of contaminated sediments. G. japonica was found in the main channel of the salt marsh at the south end of Netarts Bay.

Protohyale frequens and Parallorchestes americana
Hyalid Amphipods
Alaska to California
Family Hyalidae
Native

Protohyale frequens, one of the most abundant intertidal amphipods along the Pacfic coast, is often associated with seagrass Phylospadix and coralline algae. I’ve consistently found it among California mussels. Hyalids are gammaridean (sub-order Gammaridea) amphipods, the principal group in the order Amphipoda. There are many species of marine gammarids, often difficult to identify. Some are epibenthic, some burrow into sediments, some house themselves in tubes they make from sand, shell or plant fragments, and a few are planktonic. Most gammarids are detritus feeders or scavengers; some are herbivorous. There are males and females, and females brood their eggs. They have some superficial resemblances to isopods, but most gammarids are flattened from side to side whereas isopods are dorsal-ventrally flattened.

Another similar free-swimming Hyalid, Parallorchestes americana (as listed in the Light and Smith Manual, but the name may not be officially accepted), was found among red algae. Both amphipods are around five millimeters long.

Protohyale frequens

Parallorchestes americana

Crangon nigricauda
Blacktail Crangon
Alaska to Mexico
Family Crangonidae
Native

The Blacktail Crangon Crangon nigricauda ranges from Prince Williams Sound in Alaska to Baja California, and from intertidal to depths over 200 meters. Despite its name, its tail is not always black. It may feed on a variety of invertebrates depending on prey size, availability and water temperature and salinity, but in San Francisco Bay, at least, it favors amphipods. It is fed upon by crabs, including Dungeness, and fish. Young Blacktails can be found more often in shallow, warmer, low salinity estuarine waters, whereas adults move to deeper, cooler, more saline water. Females go further up estuaries than males. These latter observations were from Yaquina Bay estuary, a riverine estuary with the Yaquina River flowing into Yaquina Bay, and its associated upstream variations in salinity, temperature, and depth, and may not apply to Netarts Bay which is shallow and has little freshwater input. Spawning in Yaquina Bay is from December to August.

Lissocrangon stylirostris
Smooth Crangon
Alaska to California
Family Crangonidae
Native

The Smooth Crangon Lissocrangon stylirostris favors open wave-swept beaches where it buries in the sand to escape predators. It feeds mostly at night on the mysid Archaeomysis grebnitzkii, and is fed upon by fish, including English Sole and then Pacific Staghorn Sculpin. During the day it may bury deeper into the sand, kind of a diurnal vertical migration, coming out at night to feed. When you find this shrimp, you may see a bulge along the side of the carapace. Under the carapace you will find the parasitic isopod Argeia pugettensis which reduces growth, inhibits food capture, and may sterilize females. The Smooth Crangon's life span is one to two years. The genus Lissocrangon from Greek literally means smooth shrimp (liss=smooth, crangon= shrimp). This shrimp is also under the genus Crangon.

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.
Click here for more information!

Upogebia pugettensis/Neotrypaea californiensis.
Blue Mud Shrimp/Ghost Shrimp
Alaska to Central California/Alaska to Mexico
Family Upogebiidae/Callianassidae
Native

On the edges of Netarts Bay, in the soft mud and silt where you can easily sink up to your shins, we often see hundreds of holes, all close together. These are the burrows of two crustaceans, the Blue Mud Shrimp Upogebia pugettensis and the slightly smaller Ghost Shrimp (locally called a Sand Shrimp) Neotrypaea californiensis. Each can grow to three to four inches long. Many locals know these two shrimps because they are hunted for bait, usually by using suction devices call "shrimp guns". The easiest way to tell the two apart is by the first pair of legs, the pincers (chelipeds): those of the ghost shrimp are of unequal size one with a large pincer (cheliped), especially in males, and those of the mud shrimp are equal with somewhat pincerlike or subchelate claws (however, they can still pinch). The ghost shrimp is white to pink to red whereas the blue mud shrimp is a pasty blue-gray.

The Blue Mud Shrimp live in a well-kept, U-shaped or Y-shaped burrow with two, three or more entrances and smooth sides, smooth because the shrimp secretes a coating. The burrow may extend downward from the surface around a foot and a half and laterally from two to five feet with some expanded places for the shrimp to turn around. Both a male and female will inhabit a burrow. They dig their burrows with their first two pairs of legs, the chelipeds, which loosen the mud, and then use the second pair of legs, which have hairy fringes that can form a kind of basket, to carry the mud to the surface.

Upogebia feeds on plankton, detritus, and the bacteria that cling to the detrital particles. It does so by bracing itself on the sides of the burrow and using fan-like swimmerets (the pleopods) attached to the underside of the abdomen to create a current that circulates water and food through the burrow. It strains the food from the water with the second pair of legs using their hairy fringes. The external mouth parts, the two pairs of maxillipeds, then move the food to the mouth.

Ghost Shrimp inhabit less orderly, less permanent, but more complex and constantly reworked burrows with many branches that may be as deep as thirty inches. They pump water through their burrows for respiration but not for capturing food as do mud shrimp. They feed by sorting through mud particles for detritus, and they go through a lot of mud for a meal. They use their second and third pairs of legs to loosen the mud, then use hairs on the same legs to sieve out the detritus which is transferred to the mouth.

Females of both shrimp brood several thousand eggs attached to their swimmerets for several weeks. The eggs hatch during late spring and summer, releasing larvae into the estuary. The larvae move into the ocean, then after several weeks return to the estuary where they eventually burrow into the mud.
Neither of the shrimp are alone in their burrows. They have roommates, including a goby fish, pea crabs, copepods, other shrimp, a scale worm, and a commensal clam Orthione rugifera that uses byssal threads to attach to the underside of the abdomen of Upogebia.
Populations of Upogebia in some areas have suffered severe declines from a parasitic isopod, Orthione griffenis (Griffen's isopod), introduced from Asia in the 1980's from ship's ballast waters. The isopod resides under the carapace next to the gills where it sucks the shrimp's blood leaving it infertile. Neotrypaea californiensis is not affected, but it can carry a native parasitic isopod Ione cornuta.

Both shrimp have been a problem for oyster growers in Oregon and Washington. Their burrows make the sediment soft and oysters sink into the mud and suffocate. In addition, as burrows are excavated, especially by ghost shrimp which are continually revamping them, the sediment brought to the surface will bury oysters. Oyster growers have traditionally used the pesticide carbaryl to keep the shrimp in check, but that is now being phased out. Griffen's isopod may inadvertently help the growers as a biological control.

Upogebia pugettensis

Neaeromya rufifera

Orthione griffenis

Neotrypaea californiensis

Neotrypaea californiensis burrows

Hemigrapsus oregonensis
Oregon Shore Crab
Alaska to Mexico
Family Varunidae
Native

The Oregon Shore Crab is the easiest to find. Just look under almost any rock at the edge of the bay and you will see them scurry. You can identify them by their hairy legs. They come in a variety of shades from creamy white the dark brown. They also live in burrows along the muddy banks and channels of the salt marsh. This crab is found in quiet waters all along the Pacific coast. It is a opportunistic omnivore, feeding mostly on green algae and diatoms but also eating snail eggs and small invertebrates. It can tolerate the fine sediments in these muddy burrows because a mat of bristle-like setae at the openings to their bronchial chambers, which contain their gills, block the entrance of mud grains.

Gregory Jensen and Michael Egnotovich (University of Washington) examined the color polymorphism, that is the variable white, creamy, and dark blotchy patterns that appear on the carapace and legs. They found that it is dependent on age (especially the young), sex, substrate colors, and the presence and color of chromatophores (pigmented cells) in the hypodermis. The color patterns that match substrates, such as white sand beaches or dark cobbles and rocks, offer protection against predation. Crabs with the appropriate chromatophores (melanophores) can adjust their color patterns to match changes in substrate colors.

Hair on legs

Pachygrapsus crassipes
Lined Shore Crab
Washingto to Mexico
Family Grapsidae
Native

The Lined Shore Crab lives in rocky intertidal areas or where there is hard mud. It is lively and scurries quickly into crevasses or under rocks when disturbed. Its vertical range is from mid-intertidal to the splash zone. Those living in the higher intertidal zones will move into the water periodically to wet their gills, but otherwise may stay out of the water for up to three days. It is omnivorous, feeding more often at night on green, red and brown algae, diatoms, worms, limpets, snails, isopods, and other shore crabs. Females become gravid in late spring and summer. Individuals live about three years. We are near the northern extent of their range which is from southern Washington to Mexico.
You can find it on the rocky outer coast and in the rip rap along the east side of Netarts Bay

Cancer productus
Red rock Crab
Alaska to Mexico
Family Cancridae
Native

Another crab you may recognize is the Red rock Crab Cancer productus, prevalent in Netarts Bay, especially among the sub tidal riprap rocks on its eastern side. It is smaller than the Dungeness and not commercially harvested, but it is still tasty. The top of its shell is brick red, thick, and its pincers have black tips. Its young may be colored with spots or stripes. It is a predator, eating barnacles, small crabs, and many other live prey, including oysters which can be a problem for oyster farmers, and it will scavenge dead fish. It is preyed upon by coastal fish such as sculpins.

Red Rock Crabs mate in the summer after the female has molted, then the male will often protect the female by clasping her against his abdomen until her shell hardens. Male spend the winter in shallow waters, females in deeper areas.

Romaleon antennarium
Spot-Bellied Rock Crab, Pacific Rock Crab
British Columbia to Mexicio
Family Cancridae
Native

More common in California but also found occasionally in Netarts Bay, Romaleon antennarium (Formerly Cancer antennarius) can be recognized the bright red spots on its creamy white belly and its dark-tipped claws. It can grow to more than six inches (150 cm), the males even larger. It lives mostly along shallow sandy areas of protected waters of the outer coast and hides under rocks. It is a scavenger as well as a predator. Its diet includes bivalves, snails, echinoderms, and hermit crabs. It is preyed upon by large fish, octopuses, sharks, and otters.

Netarts is close to the northern end of its range. A few are found in Puget Sound and in southern British Columbia, but in California it is prevalent enough to support small sport and commercial fisheries.

Pugettia producta
Northern Kelp Crab
Alaska to Mexico
Family Majidae
Native

The Northern Kelp Crab Pugettia producta is one of the so-called spider crabs that does not typically decorate itself with pieces of algae, sponge or other organisms and keeps its shell fairly clean. However, when it does decorate, it is usually with foods such as various algae that it will eat later. Old crabs which no longer molt may have barnacle hitchhikers. Their favorite food is algae, mainly brown kelps and reds, but will eat clams, mussels and other animals when algae is scarce, particularly during winter. It is in fair abundance in Netarts Bay, often around rocks. Its shell ranges in color from light olive to dark brown, and its ventral side is tinged with red.

Juvenile kelp crabs can be found in the bay clinging to the Japanese sargassum seaweed during July and August.

Juvenile

Pinnixa faba/ Pinnixa littoralis
Pea Crabs
Alaska to California
Familiy Pinnotheridae
Native

A curious group of brachyurans that inhabit the mantle cavities of clams, oysters and mussels belong to the family Pinnotheridae, the Pea Crabs. There are fifteen species of pea crabs in Oregon, but two of the most encountered are the closely related Pinnixa faba and Pinnixa littoralis, both of which live in the same two gaper clams (Tresus capax and Tresus nuttalllii). These two crabs are difficult to tell apart without a strong hand lens or a microscope. One feature is the shape of the distal eye orbits. Those of P. faba are oval, whereas those of P. littoralis are angular. These two pea crabs live in pairs, mature male and female, in the mantle cavity of the clams and are considered parasitic because the steal food from the clam and don't appear to benefit the clam in any way. Juveniles may also occupy the clam but do not mature until an adult dies. Females are larger than males. Gaper clams are not the only host. Both crabs have been found associated with other clams, sea cucumbers, tunicates, abalone, and limpets.

Another pinnotherid you will encounter in Netarts Bay clams is the Grooved Mussel Crabs Fabia subquadrata. Smaller than Pinnixa sp., it inhabits mussels (including California and Bay Mussels and the Horse Mussel), soft shell clams, gaper clams, and other bivalves, and only one individual crab at a time, not as male-female pairs. Fabia is considered a parasite in the classical sense for the same reasons mentioned above. Pictured to the right is a pinnotherid from the Littleneck Clam Leukoma staminea, only five millimeters wide across the carapace. Some pinnotherids live in tube worms and other organisms.

Small pea crab from the Little Neck Clam Leukoma.

Carcinus maenas
European Green Crab
British Columbia to California
Family Carcinidae
Non-native

A recent invader into Netarts Bay is the European Green Crab Carcinus maenas. It was first reported in Willapa Bay in 1961, then in San Francisco Bay in 1989 but probably arrived in California prior to that date. Its pelagic larvae spread up the coast through Northern California, Oregon, and into British Columba in the 1990s, especially during the 1997/1998 El Nino when strong currents pushed them northward. Its vectors probably include ballast water from ships and live seafood shipments from the Atlantic. They compete with native crabs, Dungeness and Red Rock especially, for food including clams, mussels, and other crabs. They also eat young oysters and have the potential to severely impact the local oyster industry. If you catch the European Green Crab, do not return it to the bay. Drop the crab off at an ODFW office, either live or frozen, with catch information (where and when caught), so populations of green crabs can be tracked.

Its color is more a dark reddish brown or greenish brown than green, but it can be identified by five prominent spines on each side of the carapace. They are increasing in size and number in Netarts Bay.

Click on the following links to find more information on the European Green Crab.

http://www.dfw.state.or.us/MRP/shellfish/crab/crab_identification_specifics.asp
http://wdfw.wa.gov/ais/carcinus_maenas/

Emerita analoga
Pacific Mole Crab
Alaska to Mexico
Family Hippidae
Native

Another group of crabs is the infraorder Anomura, which includes hermit crabs, galatheid crabs, king crabs, porcelain crabs, mole crabs, and sand crabs. Anomuran crabs have been described as kind of a transition between shrimp and true crabs. Some, like the porcelain crabs, look very crablike, while others, such as the mole crab, don't look crablike at all.

The Mole Crab, Emerita analoga, is one of the unmistakable characters of our spring and summer beach. We can see both adults and their young. Its egg-shaped body is hydrodynamically sculptured for living in wave-pounded and shifting sands. Mole crabs are gregarious and can be found in shoals, washing in and out with the surf and the tide, sometimes becoming stranded on the beach. They are called mole crabs, of course, because they burrow, but only in wet sand. They cannot dig in sand that is too dry or firmly packed. It has to have enough water to separate the grains and make the sand penetrable.

Mole crabs are herbivores, feeding on dinoflagellates and diatoms, and they feed when the waves recede. Using its legs, a crab will burrow backwards into the sand during an incoming wave. It head is pointed upward facing the surf, its stalked eyes and its small first antennae, which it uses as kind of a snorkel for respiration, projecting from the sand. When a wave goes out, it curls its large, feathery second antennae backward and uses them as nets to capture the phytoplankton. The food is scraped from the antennae by other specialized, brush-like appendages and delivered to the mouth.

Males, smaller than females, are often found higher up on the beach. In fact, larger individuals of both sexes like the deeper surf. A single female can carry more than 20,000 bright orange eggs. The free-swimming zoea larvae are pelagic for three to six months and can be transported long distances by ocean currents. Juveniles may wash up in dense swarms onto beaches where they burrow just under the sand's surface, giving the beach a lumpy appearance. During the spring our beaches may be invaded by massive numbers of juveniles, possibly hundreds of thousands or more per square meter. A small handful of sand can yield hundreds, each individual about five millimeters long. Very few juveniles reach adulthood. Most, when washed back out to sea, become food for other animals. Adults are also food for a variety of shorebirds, and they are a favorite food of surfperch. When I was a kid, I used mole crabs as bait when fishing for surfperch.

Juveniles

Petrolisthes cinctipes
Flat Porcelain Crab
British Columbia to Mexico
Family Porcellanidae
Native

A common anomuran we find in Netarts Bay is the Flat Porcelain Crab Petrolisthes cinctipes located under the mid-intertidal riprap rocks along the east side of the bay. It can also be found in beds of California mussels on the outer coast. Native from British Columbia to Mexico, it is eurythermal - surviving a wide range of temperatures - and it can remain out of water for some hours between tides. It's colored brown or bluish brown but can be identified by red mouthparts. They have long antennae that are often folded back posteriorly. P. cinctipes appears to have only four pairs of legs, but the fifth pair is reduced and folded over the back part of the carapace . These legs have small pincers used for gill cleaning, egg grooming, etc. (Thanks to Gregory C. Jensen for this information.) When you lift up a rock, you will find they are active and quickly scurry under other rocks to hide. It is called the porcelain crab because it readily loses claws and legs if handled - as if they were made of porcelain.

It can also tolerate a fairly wide pH range, the extremes of which (6.9 -9.2) occur in the intertidal zone for short periods of time, but prolonged exposure to a less than average low pH (7.6) causes a lower survival rate in juveniles. This has serious implications regarding ocean acidification, which has already had an impact on the oyster industry in Netarts Bay.

Red mouth parts

Pachycheles pubescens
Pubescent Porcelain Crab
British Columbia to Mexico

Pachycheles rudis
Thickclaw Porcelain Crab
Alaska to Mexico
Family Porcellanidae
Native

A couple of other porcelain crabs the Thickclaw Porcelain Crab Pachycheles rudis and Pubescent Porcelain Crab Pachycheles pubescens. These two have fatter claws than does Petrolisthes. Both are found in rocky intertidal tide pool areas under stones or in empty burrows left by boring clams. Both range from Canada to Mexico but P. rudis is more common in the southern part of the range and P. pubescens in the northern part. You can identify the two by the number of plates at end of the abdomen which is curled under the body: P. rudis has five, P. pubescens has seven. Also, the lower part of the cheliped's propodus is hairy on P. pubescens.

Both crabs are predators during their free-swimming zoeal stages, capturing live prey upon contact (they don't really hunt). They then become filter feeders after metamorphosing into megalopa (a later larval stage) and growing into adults, straining out and trapping food particle such as plankton and detritus with the setae on their outer mouth parts, then sorting them with the inner mouth parts.

Pachycheles rudis

Carpus of P. pubescents with serrated teeth on anterior margin; Cheliped with hairs

Pagurus hirsutiusculus
Hairy Hermit
Alaska to California
Family Paguridae
Native

The Hairy Hermit is very common in intertidal tidepools and protected waters. You can identify it by its banded antennae, a white band at the distal end of the propodus (second segment) of the walking legs, and a blue dot at the other end. It is a speedy hermit crab and uses its quickness to escape predators such as sculpins. It prefers light shells that don’t imped it mobility, and it may abandon a shell if handled or confronted by a predator. It can withstand total immersion for long periods, even years, and it is tolerant brackish water. It feeds mostly on detritus and seaweeds and can, if the opportunity is there, eat live animals. It broods its young. It has setae on its minor cheliped that are sensitive to calcium and help the crab select appropriate shells.

White band and blue dot on the propodus.

Cirolana harfordi
Scavenging Isopod
British Columbia to Mexico
Family Cirolanidae
Native

This little isopod is common in mussel beds along it entire range. You can also find it sometimes under rocks from high to low intertidal zones. It is called a scavenger, and it does scavenge among the barnacles and mussels for whatever dead animals it can find, but it is also a voracious predator, feeding on polychaetes and amphipods. It finds dead animals by chemoreception. If a dead fish is detected, swarms of Cirolana will cover the fish and devour its flesh until only bones are left. Its digestion is slow, it can live on a single meal for a month, so it will retreat to safe hiding places, like mussel beds, to avoid predators. You can easily recognize this stubby isopod by its fan-like uropods and endopods - its “tail fan”, that stick outward like the tail feathers of a bird.

Pentidotea wosnesenskii
Rockweed Isopod
Alaska to Mexico
Family Idoteidae
Native

Formerly Idotea wosnesenskii, you can find this isopod on seaweed, rock grass, and coralline algae on the wave-swept rocks of the open coast. Locally, look for it in the lower intertidal rocks of Tunnel Beach, often clinging to rock grass Phylospadix scouleri. The hooked claws on its walking appendages (peripods) allow it to hold on in even heavy surf. It is one of the largest and most common intertidal isopods, reaching an inch and a half (4 cm) long. Colors vary from a patterned pink when living with coralline algae to brown and even green when associated with kelp or rock grass. These color adaptations are true for several related species. Sexes are separate, and males are larger than females. Development is direct. Fertilized eggs and young are brooded by the female, and the larvae (manca larvae) resemble small adults. It is herbivorous, eating kelp and rock grass blades. Picture 1 is the color pattern when living on coralline algae; Picture 2 are two individuals found on rock grass, one clasping a juvenile.

Ligia pallasii
Sea Slater, Rock Louse
Alaska to Central California
Family Ligiidae
Native

The Sea Slater Ligia pallasii, sometimes called the Rock Louse, lives high or above the splash zone along the rocky cliffs of the outer coast, usually in rocky caves or crevasses out of direct sunlight and where there may be some freshwater seepage. These supralittoral dwellers are most active at night, feeding on algal films, decayed algae, and animal detritus. They are air breathers, breathing through their abdominal appendages, the pleopods. They are sexually dimorphic (males and females look different), the males larger with projecting lateral plates and may reach a couple of inches long. Females are smaller. L. pallasii are most commonly seen during late spring and summer during their breeding season. Fertilization is by copulation. Embryos are brooded by the female, and development is direct. There is no free larval stage.

male

Balanus glandula
Sharp Acorn Barnacle
Alaska to Mexico
Family Balanidae
Native

The Sharp Acorn Barnacle Balanus glandula is the most common intertidal barnacle along the Pacific Northwest Coast. It ranges from Alaska to Northern Mexico and inhabits the high splash zone to subtidal. It is white, less than an inch in diameter, and attaches to substrates with a basal calcareous plate. These plates are evident where the barnacles have been broken off rocks by heavy waves along the open coast. It is conical like a miniature volcano, with a rather diamond shaped aperture at the top of the "shell." This aperture allows the animal's access to its outside environment, for feeding, waste removal, respiration, and reproduction. It is covered by four plates, two terga two scuta, that can be closed for protection and to prevent water loss or opened to allow feeding. It feeds by sweeping its cerri (feet) through the water to capture small plankton.

B. glandula is very adaptable, withstanding drying from exposure, tolerating temperature and salinity extremes, and going long periods without food. If crowded, it will grow tall and skinny, accommodating adjacent barnacles. Barnacles are hermaphroditic. The eggs are brooded, then when hatch, they release a free-swimming larva called a nauplius which is succeeded by a cypris larva. The cypris settles on to a hard substrate, usually preferring some kind of crack or indentation to gain a purchase.

Another similar but smaller barnacle Chthamalus dalli occurs with B. glandula from Alaska to Mexico, but it's more brownish, has a more rounded aperture, and has a different arrangement of its rostral side plate. It is also more common closer to the southern parts of its range. I have not found it here.

Crowded barnacles

B. glandula settled into rock cracks

Banacles settled in shallow holes drilled into a pvc test panel

Barnacle cerri

Balanus nubilus
Giant Acorn Barnacle
Alaska to Mexico
Family Balanidae
Native

The Giant Acorn Barnacle Balanus nubilus may be seen along the entire intertidal and subtidal rocky coastline from Alaska to Mexico. Locally, look for it in the rocks at Tunnel Beach in Oceanside. This by far is our largest barnacle, reaching up to six inches across. It is reputed to be even the world's largest. Here, we find it mostly solitary, but it can in some areas group together to form reefs. It has a thick calcareous base that is attached to rocks, pilings, and other hard substrates. The cerri are pink and are easily seen as they fan through the water when the animal is submerged. It is hermaphroditic, and the eggs are brooded until they hatch as nauplii. A major predator is the Ocher Star Pisaster ochraceus. Empty shells serve as refuges for small fish, octopuses, and crabs. Its shell is sometimes eroded by the boring sponge Cliona. B. nubilus has some very large muscle fibers that have been used in the study of muscle physiology.

Semibalanus cariosus
Thatched Acorn Barnacle
Alaska to Southern California
Family Archaeobalanidae
Native

The Thatched Acorn Barnacle is often part of a California mussel and barnacle assemblage living on surf-pounded rocks of the outer coast. It may grow on the mussels, rocks, wood, or other hard substrates. It ranges from Alaska to Southern California. The shell, which can be more than two inches across, is heavily ridged, the striations running along the sides from the aperture to the base. Unlike Balanus, it has a membranous, not a calcareous, basal plate. But like Balanus, if crowded, they can grow vertically so they are tall and thin. S. cariosus can live in conditions from the dry splash zone, to heavy pounding wet waves, to calm bay waters. Its cerri are dark brown to black. It is preyed upon by the sea star Pisaster and birds.

The mussel-barnacle assemblage with Mytilus, Semibalanus, and Pollicipes.

Pollicipes polymerus
Goose-Neck Barnacle
Alaska to Mexico
Family Scalpellidae
Native

A strange and distinctive looking barnacle, the Goose-Neck Barnacle, lives in the mid to upper intertidal zones of surf-exposed shores, most often in association with the California Mussel Mytilus califorianaus and the Thatched Acorn Barnacle. This assemblage in which patches of Pollicipes are interspersed between the mussels, and Semibalanus lives either attached to rocks on which the other two live, or more often to the mussel's shell, is an example of competitive interaction within an ecological community where, in this case, the competition is for space. This complex assemblage houses other interacting species that are discussed in a section on the California Mussel.

The Goose-Necked Barnacle is attached to substrates by a flexible, rubbery stalk (the peduncle) with a set of interior muscles and an outside leathery covering that is coated with tiny scales. At the end of the peduncle is the capitulum which contains the animal's body and is enclosed by a series of protective, chalky-colored, calcareous plates that correspond to those of the acorn barnacles, but with additional plates. The barnacle can move the plates to form an opening to allow the extension of the cerri for feeding. Pollicipes is an omnivore, feeding on both phytoplankton and zooplankton. Unlike the acorn barnacle, it does not sweep its cerri, but spreads them as a net during the backwash of a wave that has broken over the mussel-barnacle bed, catching food in the runoff. Like other barnacles, Pollicipes is a hermaphrodite with its gonads located in the peduncle. It does not self-fertilize but relies on cross fertilization. By the way, the interior muscle portion of the peduncle is edible and considered by some a delicacy.

Another goose-necked barnacle, the Pelagic Goose-Necked barnacle Lepas sp. in the family Lepadidae, is not native but we find in washed ashore attached to flotsam.

Lepas sp.