Goose barnacles are marine crustaceans found clinging to various ocean surfaces. Their distinctive appearance can lead to them being mistaken for a shellfish or plant. These creatures are distant relatives of crabs and shrimp, belonging to the group of crustaceans known as Cirripedia.
Defining Features and Habitat
Goose barnacles have an unusual physical structure, including a long, muscular stalk called a peduncle. This peduncle, which anchors the barnacle to a hard surface, can range in color from orange to dark brown or black. The stalk can vary significantly in length, with some species having peduncles up to 80 cm long. At the end of this stalk is the main body of the barnacle, known as the capitulum, which is covered by several white, chalky shell plates. The number, color, texture, and size of these plates differ among species.
Unlike acorn barnacles, which have a compact, conical shell directly attached to a surface, goose barnacles possess this flexible stalk. This shape, resembling a goose’s neck and head, earned them their common name. Goose barnacles thrive in exposed coastal areas and intertidal zones, preferring habitats with strong wave action. They attach to various substrates including rocks, floating debris, and boat hulls. Attachment is achieved through a strong, durable adhesive produced by cement glands in their peduncle.
Life Cycle and Feeding
Goose barnacles are filter feeders, obtaining nutrition by sieving microscopic organisms and organic particles from seawater. They use feathery appendages called cirri, which extend from their capitulum. These six pairs of cirri act like a net, capturing plankton and detritus from the water. Once food particles are trapped, the cirri withdraw into the capitulum, and the captured nutrients are then transferred to the barnacle’s mouth. This filter-feeding behavior helps in nutrient cycling within their intertidal ecosystems.
Goose barnacles are hermaphroditic, possessing both male and female reproductive organs. While they have the capacity for self-fertilization, cross-breeding is more common and promotes genetic diversity. Fertilization typically occurs when one barnacle extends its long penis to deposit sperm into a neighboring barnacle’s mantle cavity. Some species can even engage in “spermcast mating,” where sperm is released into the water and captured by other barnacles.
After eggs are fertilized, they are brooded within the mantle cavity. Larvae, known as nauplii, are then released into the ocean to drift as zooplankton. These weak-swimming larvae feed on phytoplankton. They then develop into a cyprid stage, which is non-feeding but capable of strong swimming, seeking a suitable place to settle. Larvae are sensitive to chemical cues from established barnacles, indicating favorable conditions for settlement. Once a suitable substrate is found, the cyprid larvae undergo metamorphosis, transforming into sessile adult goose barnacles.
Interaction with Humans
Goose barnacles hold a special place in culinary traditions, particularly in Spain and Portugal, where they are known as “percebes.” They are considered a sought-after and expensive delicacy, prized for their oceanic flavor. The taste of percebes is often described as a blend of lobster and clam, with a tender yet slightly chewy texture and a distinct brininess. They are typically prepared simply, often boiled briefly in salted water, allowing their natural taste to be the highlight.
Harvesting percebes is a dangerous endeavor due to their habitat on wave-battered rocks in intertidal zones. Harvesters, known as “percebeiros,” risk their lives navigating treacherous cliffs and powerful waves to pry the barnacles from the rocks. This perilous collection method contributes significantly to their high market price.
Beyond culinary appeal, goose barnacles can also attach to marine structures and vessel hulls, a process known as bio-fouling. This attachment can impact the efficiency of ships and require maintenance to remove. Historically, goose barnacles were even mistakenly believed to be the embryonic form of barnacle geese, a myth that persisted due to their appearance and and the lack of observed nesting grounds for the geese.