Mitella polymerus (Sowerby, 1833)
Goose Neck Barnacle, Leaf Barnacle
|Synonyms: Mitella polymerus|
|Rosette of Leaf Barnacles (Pollicipes polymerus) at Swirl Rocks, WA. Approximate length of capitulum is 3 cm.|
|(Photo by: Melissa McFadden, June 2002)|
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.
Geographical Range: This species of barnacle is found as far north as Southeast Alaska to Baja California in the south.
Depth Range: P. polymerus occurs in the high to middle intertidal zones.
Habitat: This barnacle prefers open, surf-swept coastlines. It has also been reported to occur on other barnacles on the skin of Humpback Whales.
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
sea star (Pisaster ochraceus) and the Glaucous-winged Gull (Larus
M. polymerus directly competes with the California
Mussel (Mytilus californianus) and can often out-compete them, but they are more vulnerable to predation by gulls.
often grows in tight bunches (rosettes) 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
Note: The genus Pollicipes has an unusual distribution of W. Europe, NW Africa, and W North and Central America (Newman and Killingsley, 1985; Newman 1987, 1992). Newman attributes this distribution to a relict of the Tethys Sea.
Brandon and Rokop, 1985
Johnson and Snook, 1955
McConnaughey and McConnaughey, 1985
Morris et. al. 1980.
O’Clair and O’Clair, 1998.
Ricketts et al., 1985
Newman, W.A., 1987. Southern hemisphere endemism among the barnacles: Explained in part by extinction of northern members of amphitropical taxa? Bulletin of Marine Science 4(2): 603-619
Newman, W.A., 1992. Biotic cognates of eastern boundary conditions in the Pacific and Atlantic: Relicts of Tethys and climatic change. Proceedings of the San Diego Society of Natural History 16: 1-7
Newman, W.A. and J.S. Killingsley, 1985. The north-east Pacific intertidal barnacle Pollicipes polymerus in India? a biogeographical enigma elucidated by 18O fractionation in barnacle calcite. Journal of Natural History 19(6): 1191-1196
Wootton, J.T., 1993. Size-dependent competition--effects on the dynamics vs the end-point of mussel bed succession. Ecology 74:1 pp. 195-206
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Pollicipes polymerus at Slip Point, Clallam Bay, WA. Photo by Dave Cowles, 7-1997
A cluster of Pollicipes polymerus under a boulder at Cape Flattery. Photo by Dave Cowles, July 2004
Gooseneck barnacles often compete with California mussels for space (and if undisturbed, the mussels usually win). Photo by Dave Cowles, Shi Shi Beach, Sept 2005