Pouce Pied Canadien

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.

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.

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

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.

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.