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Goose Necked Barnacle

Pollicipes polymerus Sowerby 1833

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Gooseneck barnacles are sometimes called such because of their long necks like those of geese. There are many myths that explain the naming of gooseneck barnacles. One of which thought these barnacles to be the source of geese. The myth says that geese grow from these barnacles, which is evident from their growing feathers (cirri) from their shells (Britannica, 1999-2000).

Scientists have also used the name Mitella polymerus for this species (Kozloff 1996)

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Garand, C. 2001. "Pollicipes polymerus" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Pollicipes_polymerus.html
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Conservation Status

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Pollicipes polymerus is not endangered, and is abundant along the Pacific coast. The only risk of lowering numbers is if the gooseneck barnacles are overused as a food source for humans (Britannica, 1999-2000).

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Garand, C. 2001. "Pollicipes polymerus" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Pollicipes_polymerus.html
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Cari Garand, Western Oregon University
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Benefits

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Pollicipes pollicipes is a barnacle that is found in the intertidal of Portugal and Spain. There they are considered a delicacy, and served in gourmet restaurants. Due to local harvesting, their populations become depleted at times. They then seek sources outside of their countries and will then import P. polymerus as a substitute for P. pollicipes, thus bringing in money for the United States (Britannica, 1999-2000).

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Garand, C. 2001. "Pollicipes polymerus" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Pollicipes_polymerus.html
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Cari Garand, Western Oregon University
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Karen Haberman, Western Oregon University
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Trophic Strategy

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Pollicipes polymerus is a filter feeder. Since its head is attached to a usually rocky surface, P. polymerus feeds by extending its legs, or cirri, from its "shell". It separates the valves of its shell and extends the feathery cirri into the water when the tide is in, or when water runs down rocks. Pollicipes polymerus often orients itself to face the current. This explains why, when seen, most are facing the same direction. Pollicipes polymerus will eat a variety of food and is not not selective. Most of its diet consists of small organisms such as plankton, cypris larvae, small clams, hydroids, and amphipods. Food is caught in a lassoing action of the cirri. Six pairs of cirri contract and force the food down towards the mouth parts. Catching the food is aided by many small hairs that line the sides of the segmented cirri. These hairs also aid in the movement of food towards the mouth parts. Since food may be hard to come by at times of low tide, Pollicipes polymerus can use some of its cirri to pass food to the mouth while using others to catch and hold onto new prey when food is abundant.

Animal Foods: mollusks; zooplankton

Plant Foods: phytoplankton

Foraging Behavior: filter-feeding

Primary Diet: planktivore

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Garand, C. 2001. "Pollicipes polymerus" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Pollicipes_polymerus.html
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Cari Garand, Western Oregon University
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Karen Haberman, Western Oregon University
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Distribution

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Pollicipes polymerus is found from the southern region of Alaska to Baja, California (Lane C.C., 2000).

Biogeographic Regions: nearctic (Native )

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Garand, C. 2001. "Pollicipes polymerus" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Pollicipes_polymerus.html
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Cari Garand, Western Oregon University
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Karen Haberman, Western Oregon University
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Habitat

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Pollicipes polymerus is found on rocky cliffs in the splash zone. They inhabit very high-energy environments because they can withstand the wave pressure very well. They receive minimal exposure to water; at the most, once a day. They are most often found within cracks and crevices in rocks to minimize their exposure to sunlight, which helps prevent desiccation. Pollicipes polymerus is most commonly found in colonies of many other gooseneck barnacles. They often grow on each other. You can find many smaller goosenecks on the stalk of larger ones. Within the colony the larger goosenecks are found in the center surrounded by the smaller ones in the periphery. They are also very likely to be seen amongst California mussel (Mytilus califonianus) beds (Eckman and Duggins, 1993; Hilgard, 1960; Lane C.C., 2000).

Aquatic Biomes: coastal

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Garand, C. 2001. "Pollicipes polymerus" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Pollicipes_polymerus.html
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Cari Garand, Western Oregon University
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Karen Haberman, Western Oregon University
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Morphology

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Pollicipes polymerus can be distinguished by its long neck, or stalk. This part of its body is usually 1 inch long. It ranges in color from reddish-brown to brownish-black. The stalk has a leathery appearance with a texture of small bumps. The shell, or capitulum, of P. polymerus grows to be about 2 inches long. It is made up of small plates which enclose its soft body. Inside the shell, the barnacle primarily consists of long segmented legs, intestines, and stomach. The gonads are held within the stalk. The stalk also contains the gland which is used to produce the adhesive that allows barnacles to attach to rocks so well. Pollicipes polymerus can reach up to 8 inches in length (Chase, 1997; Abbott et al., 1980).

Other Physical Features: ectothermic ; bilateral symmetry

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Garand, C. 2001. "Pollicipes polymerus" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Pollicipes_polymerus.html
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Cari Garand, Western Oregon University
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Karen Haberman, Western Oregon University
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Associations

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P. polymerus is a main food source of Glaucous-winged gulls. The gulls eat them on exposed shores, eating the capitulum and leaving the stalk. They are also a food source for sea stars and whelks (snails)

Known Predators:

  • glaucous-winged gulls (Larus glaucescens)
  • sea stars (Asteroidea)
  • whelks (Buccinum)
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Garand, C. 2001. "Pollicipes polymerus" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Pollicipes_polymerus.html
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Cari Garand, Western Oregon University
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Karen Haberman, Western Oregon University
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Reproduction

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Pollicipes polymerus is a hermaphrodite, meaning it is equipped with both male and female reproductive organs. These organs mature at relatively the same rate in the gooseneck barnacles. Although it is hermaphroditic, it usually will not self-fertilize unless there are no other barnacles within about eight inches. It is better for them to cross-breed because it ensures the diversity of their population. Once a female lays eggs, a pheromone is released letting those surrounding males know that she is ready. One barnacle will reach its penis over to a nearby barnacle to release sperm into the shell. Amazingly, it can reach about seven times the animal's diameter. Once the eggs in a neighboring barnacle are fertilized, they are brooded in the mantle cavity. Pollicipes polymerus has a reproductive period of about eight months, and produces about three to four broods (five to seven are possible for a large barnacle.) Thousands of nauplius larvae are then released into the ocean to fend for themselves. These larvae are weak swimmers that spend their time feeding mostly on phytoplankton. Once they reach the cyprid stage they are strong-swimming, non-feeding larvae, with a sole purpose of finding a place to settle. Pollicipes polymerus follow many cues for settlement. Once the cypris larvae have undergone metamorphosis to juvenille barnacles, they will search for a suitable home. They do so by receiving chemical cues from other established barnacles; meaning that there are good conditions. However, this could be a problem when competing for space. They also have to take into consideration the correct temperature, surface texture, and current. All of these factors are crucial for its survival. Gooseneck barnacles are thought to reach maturity at the age of five, and are considered fully grown at the age of twenty (Britannica, 1999-2000; Fox et al., 1997; Hillgard, 1960).

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Garand, C. 2001. "Pollicipes polymerus" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Pollicipes_polymerus.html
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Cari Garand, Western Oregon University
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Karen Haberman, Western Oregon University
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Fisheries Value

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In British Columbia, the Gooseneck barnacle populations dominate the mid and upper tidal ecosystems. There is a potential for high fisheries value in harvesting these gooseneck barnacles due to their great size and abundance, but the storage and transportation problems involved in the process need to be solved. Research conducted by F.R. Bernard found that optimal harvesting time is limited to May-October. In addition, the optimum storage temperature for detached and attached barnacles is 6-9 Celsius, with minimum mortality and up to 20 days in storage at 8 degrees Celsius. Quick freezing of the product may be the solution to overseas air transport, but European markets may refuse to receive frozen product for optimal prices.

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Comprehensive Description

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The body of this organism is up to 8 cm long. The capitulum is protected by five large, whitish plates and several smaller ones which lie in basal whorls. The carina lacks spines, and the tough, fleshy peduncle allows for elasticity to the force of the surface. The color is dark brown and contains many calcareous spicules embedded in its surface.
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Look Alikes

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How to Distinguish from Similar Species: There is a pelagic goose barnacle, Lepas anatifera, frequently found in the Pacific Northwest that looks somewhat similar to M. polymerus, however is has fewer plates and only occurs in the open sea and on driftwood washed ashore. There is a closely related European species, Pollicipes pollicipes, which is cooked and served as a delicacy. However, it is now in short supply and M. polymerus has been exported from British Columbia to Portugal and Spain.
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Habitat

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This barnacle prefers open, surf-swept coastlines. It has also been reported to occur on other barnacles on the skin of Humpback Whales.
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Distribution

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Geographical Range: This species of barnacle is found as far north as Southeast Alaska to Baja California in the south.
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Habitat

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Depth Range: P. polymerus occurs in the high to middle intertidal zones.
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Comprehensive Description

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Biology/Natural History: This species feeds by growing outward so that it can extend its cirri in a fan oriented perpendicular to the backwash of the waves. Small particles of detritus and tiny crustaceans get caught in the cirri, which are subsequently eaten. Predators of M. polymerus include the ochre sea star and the Glaucous-winged Gull. M. polymerus directly competes with the California Mussel and can often out-compete them, but they are more vulnerable to predation by gulls. M. polymerus often grows in tight bunches which make them more resistant to predation. In the Puget Sound, Goose Neck barnacles breed from April to October, peaking in July. Individuals are hermaphroditic, but will always cross-fertilize. Each sexually mature individual may produce up to four broods per year, with up to 20,000 developed young per brood. The young aggregate at the base of the adults, where their survival rate increases. Within one month they are able to attain independence. Current research includes energy flow within ecosystems containing M. polymerus and the accumulation of toxins within the mussel tissue. Note: The genus Pollicipes has an unusual distribution of W. Europe, NW Africa, and W North and Central America. Newman attributes this distribution to a relict of the Tethys Sea.
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Pollicipes polymerus

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Pollicipes polymerus, commonly known as the gooseneck barnacle or leaf barnacle, is a species of stalked barnacle. It is found, often in great numbers, on rocky shores on the Pacific coasts of North America.

Classification

Barnacles are classified with shrimps, crabs, isopods and amphipods in the subphylum Crustacea. They are included in the class Maxillopoda, though this class does not appear to be a monophyletic grouping.[3] They are included in the infraclass Cirripedia, the barnacles, members of which are sessile suspension feeders with two active swimming larval stages, the nauplius and the cyprid. The order Pedunculata includes barnacles attached to the substrate by stalks, the goose barnacles. The attachment is made by the cementing of the antennules of the cyprid larvae to the substrate and the elongation of that region into a stalk. Pedunculata is not itself a single monophyletic group but forms a transitional series of lineages moving towards the sessile acorn barnacles.[4] Pollicipes polymerus is included in the family Pollicipedidae.

Description

Pollicipes polymerus is attached to rocks or other objects by a strong, rubbery stalk, the peduncle, which is up to 10 centimetres (4 in) long. It has a muscular interior and the leathery surface is covered in bands of minute spiny scales on short stalks. The capitulum, at the end of the peduncle, is up to 5 centimetres (2 in) long and contains the rest of the body including all the limbs and other appendages except the first pair of antennae.[5] The outside of the capitulum bears five strengthening calcareous plates corresponding with the plates that protect an acorn barnacle. The largest of these is the carina, on the morphologically dorsal side of the capitulum, with a pair of smaller scuta and terga on either side below. Further calcification occurs from other centres on the capitulum with the formation of many small scales. The thoracic crustacean appendages are modified into feather-like cirri. They project through the aperture at the end of the capitulum and are used for feeding.[4]

Distribution and habitat

Pollicipes polymerus is found in the north eastern Pacific Ocean, its range extending from southern Alaska to Baja California. It occurs on rocky coasts in the intertidal zone and favours exposed areas where there is much wave action. It tends to occur in closely associated groups and is often abundant.[6]

Reproduction

Pollicipes polymerus is a hermaphrodite. Reproduction takes place during the summer and there may be several broods per year. The ovaries are in the upper part of the peduncle and liberate from 104,000 to 240,000 eggs at a time into the mantle cavity. Here they stick together to form egg masses. The numerous small testes lie alongside the gut. Sperm from these is passed along the extensible penis into the mantle cavity of an adjoining individual where fertilisation takes place. Self-fertilisation does not seem to occur and any individual that is more than 20 cm (8 in) from its nearest neighbour is effectively sterile.[7] The eggs are brooded for 3 to 4 weeks until they hatch into nauplius larvae and are liberated into the sea.[8] There they become planktonic and feed on phytoplankton. They grow and undergo 6 moults in about 40 days before becoming non-feeding cyprid larvae. These search out suitable places to settle where they undergo metamorphosis and attach themselves permanently to the substrate. They do this by secreting a strong adhesive substance from glands on the antennules. Settlement is stimulated by the presence of peduncles of other gooseneck barnacles, and may take place on the peduncles themselves.[7]

Ecology

Pollicipes polymerus is an omnivore. It feeds by extending its cirri through the aperture at the end of the capitulum and unfurling them. The posterior three pairs are biramous and form a net to trap particles. They are held at a suitable angle to intercept moving water and are periodically withdrawn into the capitulum with any food items that have been trapped. Here particles are scraped off by the other three, shorter pairs of cirri which have overlapping setae (bristles). The particles are then transported to the mouth where they are manipulated and sorted into edible and inedible items by the maxillae, mandibles and palps. This may be done with the help of chemoreceptors found on the appendages and near the mouth. Examination of the animal's gut contents show that it feeds on copepods, amphipods, barnacle larvae, small clams, polychaete worms and hydrozoans as well as detritus and algae.[8] Predators on gooseneck barnacles include the glaucous-winged gull (Larus glaucescens), the black oystercatcher (Haematopus bachmani), the ochre sea star (Pisaster ochraceus) and the six-rayed star (Leptasterias hexactis).[6][8]

A research study undertaken by Robert T. Paine in Makah Bay, Washington State in 1966[9] showed the importance of predators in maintaining a biodiverse community. Paine excluded the ochre sea star from an area of seabed where gooseneck barnacles and sea mussels (Mytilus californianus) predominated and found that the number of invertebrate species associated with them fell from fifteen to eight. Paine proposed the hypothesis that "Local species diversity is directly related to the efficiency with which predators prevent the monopolization of the major environmental requisites by one species".[10]

The distribution of both gooseneck barnacles and sea mussels is quite patchy. In an effort to understand this better, another study, undertaken by Wootton in 1994, excluded birds from an area where these two species were found on Tatoosh Island, Washington. In a carefully designed series of experiments he recorded the direct and indirect results on the numbers of goose barnacles, sea mussels, acorn barnacles, starfish and predatory whelks (Nucella spp.) present in the area. His results demonstrated the important part that predation by birds can play in the dynamics of gooseneck barnacle populations.[8]

Gooseneck barnacles compete with a number of other organisms in a complex struggle for survival in the limited available space in their rocky intertidal habitat. The first colonisers of bare rock are usually annual algae, soon to be followed by perennial species including coralline algae. Gooseneck barnacles, sea mussels and several species of acorn barnacles soon follow. Further competition is provided by sea palms, the large holdfasts of which may smother or squeeze out the molluscs and barnacles. Sea palms may settle on the mussels and may be carried away in storms, taking the mussels with them. Gooseneck barnacles may limit the colonisation of mussel recruits by feeding on their larvae. In areas where gooseneck barnacles predominate they may dominate until some are swept away in storms and allow in other species. In the long term, the mussels usually come to dominate as their byssal threads are able to overgrow all the other sessile organisms.[11]

References

  1. ^ Benny K. K. Chan (2010). "Pollicipes polymerus (Sowerby, 1883)". WoRMS. World Register of Marine Species. Retrieved February 1, 2012.
  2. ^ Pollicipes polymerus (Goose Neck Barnacle) ZipcodeZoo. Retrieved February 2, 2012.
  3. ^ Joel W. Martin & George E. Davis (2001). An Updated Classification of the Recent Crustacea (PDF). Natural History Museum of Los Angeles County. pp. 1–132.
  4. ^ a b Frederick R. Schram. "Cirripedia". Access Science. Retrieved February 2, 2012.
  5. ^ Pollicipes polymerus Archived 2013-01-31 at the Wayback Machine Race Rocks. Retrieved February 1, 2012.
  6. ^ a b Melissa McFadden, Hans Helmstetler & Dave Cowles (2007). "Mitella polymerus (Sowerby, 1833); Goose Neck Barnacle, Leaf Barnacle". Invertebrates of the Salish Sea. Walla Walla University. Archived from the original on February 13, 2012. Retrieved February 2, 2012.
  7. ^ a b Galen H. Hilgard (1960). "A study of reproduction in the intertidal barnacle, Mitella polymerus, in Monterey Bay, California" (PDF). The Biological Bulletin. 119 (2): 169–188.
  8. ^ a b c d "About goose barnacles". A Snail's Odyssey. Retrieved February 1, 2012.
  9. ^ Robert T. Paine (1966). "Food web complexity and species diversity" (PDF). The American Naturalist. 100 (910): 65–75. doi:10.1086/282400. JSTOR 2459379. Archived from the original (PDF) on 2010-06-05. Retrieved 2012-02-14.
  10. ^ Michael Begon, Martin Mortimer & David J. Thompson (1996). "Beyond population ecology". Population Ecology: a Unified Study of Animals and Plants (3rd ed.). John Wiley & Sons. p. 217. ISBN 978-0-632-03478-9.
  11. ^ Paul K. Dayton (1971). "Competition, disturbance, and community organization: the provision and subsequent utilization of space in a rocky intertidal community". Ecological Monographs. 41 (4): 351–389. doi:10.2307/1948498. JSTOR 1948498.
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Pollicipes polymerus: Brief Summary

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Pollicipes polymerus, commonly known as the gooseneck barnacle or leaf barnacle, is a species of stalked barnacle. It is found, often in great numbers, on rocky shores on the Pacific coasts of North America.

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