Gooseneck Barnacle, Pollicipes polymerus

Gooseneck Barnacle, Pollicipes polymerus.

Phylogeny: The Gooseneck Barnacle Pollicipes polymerus (Sowerby, 1833), is a member of the  Pollicipedidae Family of Goose Barnacles. The genus Pollicipes is one of three genera in this family, and there are four species in this genus. This species is also called the Leaf Barnacle or the Pacific Goose Barnacle. They are known in Mexico as percebe cuello de ganso. This species is not to be confused with the similarly named Pacific Gooseneck Barnacle Lepas pacifica. Goose Barnacles derive their name from the 16th century myth that geese hatched from them. The name barnacle may extend back to the medieval Latin word for goose, ” bernaca”.

Morphology:  Gooseneck Barnacles have two large calcareous plates and multiple smaller ones. The color between the plates is reddish in subtidal specimens, and black in intertidal ones. This black color acts as a sunscreen. The fleshy peduncle, or stalk, is leathery, with a rough, scaly, exterior. The peduncle may be brown or black. When submerged the thoracic appendages (modified into feathery cirri) extend from between the two large plates.  Sources vary in the maximum length of this species, from 8 cm (3.1 inches) to 15 cm (5.8 inches).

Habitat and Distribution:   Gooseneck Barnacles live in clusters, attached to rocks, pilings, and other hard surfaces. They prefer wave swept areas where water movement brings them more food. They are frequently growing within populations of  the California Mussel Shell, Mytilus californianus . They range in depth from the mid-intertidal zone to 30 m (98 feet). Gooseneck Barnacles have a limited distribution in Mexican waters and are found along the west coast of the Baja Peninsula, from the United State border south to Punta Abreojos, Baja California Sur.

Diet: Gooseneck Barnacles are sessile suspension feeders. They use their modified thoracic appendages to filter suspended food from the surrounding water. They are omnivores, consuming algae, amphipods, barnacle larvae, small clams, copepods, hydrozoans, detritus, and polychaete worms.

Predators:  Gooseneck Barnacles are prey for shore birds, crabs and sea stars.

Reproduction:  Gooseneck Barnacles are simultaneous hermaphrodites (having both male and females reproductive organs). Reproduction is sexual, with one individual inserting its penis into the mantle cavity of a nearby individual. Self-fertilization does not occur and individuals widely separated from others are unable to reproduce. The eggs are brooded for 3 to 4 weeks before being released as planktonic larva. The larva undergo several molts before metamorphosing into their sessile form.

Ecosystem Interactions: There are no known documented commensal or parasitic relationships between Gooseneck Barnacles and other species. They are among the first animal species to colonize disturbed areas, leading to a rapid increase in biodiversity.

Human Interactions:  Humans have collected and eaten various species of Goose Barnacles for many thousands of years.  They are collected for consumption by artisanal fishermen and also sold on a limited basis commercially. Commercial harvesting has caused localized population decreases.  The Gooseneck Barnacle has not been evaluated from a conservation perspective but they are common and have a large geographic range so they should be considered to be of Least Concern

Synonyms:  Mytella polymerus and Pollicipes mortoni.