Striped Goose Barnacle, Conchoderma virgatum

Striped Goose Barnacle, Conchoderma virgatum.  Length: 3.3 cm (1.3 inches). Barnacle collected off the beach in the greater Los Cabos area, December 2017. Attached to a leg of one of the spiny lobsters.

Phylogeny:  The Striped Goose Barnacle ,  Conchoderma virgatum ( Spengler, 1789), is a member of the Lepadidae family of Goose Barnacles.  The genus Conchoderma is one of four genera in this family, and there are five species in this genus. They are known in Mexico as Percibe Ganso Rayado. Goose Barnacles get their name from the belief held by naturalists in the 1500’s that these barnacles turn into geese. Our understanding has improved since then, and we now know that they are crustaceans, the same as crabs and lobsters.

Morphology: Striped Goose Barnacles attach to hard surfaces with a tough, flexible, flattened stalk (peduncle) that is scale-less. The head, thorax, and abdomen are located inside the body of the barnacle (capitulum).  The capitulum is covered by five calcareous plates. These plates are four-sided, smooth, and gray in color, with purplish-brown stripes. The plates are separated from each other, and are not clearly demarcated from the peduncle. The cirri (feeding tentacles) project from between the plates. Striped Goose Barnacles reach 7.0 cm (2.75 inches) in length, though most are less than half that long.

Habitat and Distribution: Striped Goose Barnacles are a pelagic species. They are found in open water, attached to a wide range of animate and inanimate objects such as buoys, ships, driftwood, sea snakes, whales and thirteen different species of fishes. They have a cosmopolitan distribution, being found in all the world’s oceans. In Mexican waters they are found offshore along both the Atlantic and Pacific Ocean coasts.

Diet: Striped Goose Barnacles are suspension feeders. They use their cirri to filter hydrozoans and other plankton from the surrounding water.

Predators:  Striped Goose Barnacles are preyed upon by sea birds, crabs, and fish.

Reproduction:  Striped Goose Barnacles are simultaneous hermaphrodites (having both male and females reproductive organs). Reproduction is sexual through broadcast spawning. The eggs are brooded in the mantle cavity  before being released as free-swimming nauplii. The larva undergo six naupliar instars succeeded by nonfeeding cypris larva (settling stage) which later metamorphose into adults.

Ecosystem Interactions: Striped Goose Barnacles are epibionts on marine life such as whales, turtles, and floating macro algae. They generally have limited impact on their hosts, but can, if their populations are too high, cause drag on their animal hosts. Striped Goose Barnacles have difficulty attaching themselves to some species of fish because of the mucous layer on the fishes skin. They are known to attach themselves to the ectoparasitic copepods Dinemoura latifolia, Pandarus satyrus, and Perissopus dentatus, while the copepods are attached to fish. It is thought that the copepods are more successful at attaching to slippery fish, and therefore the barnacles attach themselves to the copepods.

Human Interactions: Striped Goose Barnacles can rapidly get established, producing high biomass and abundance. They are known for fouling ship hulls and other human infrastructure, frequently requiring mechanical removal. The Striped Goose Barnacle has not been evaluated from a conservation perspective but they are common and have a very large geographic range so they should be considered to be of Least Concern.

Synonyms: Conchoderma virgata and Lepas virgata.