Gooseneck Barnacles: A literal (and littoral) fixture of our coast

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Barnacles are crustaceans, distant kin to crabs, shrimp and lobsters. Being arthropods, they have bodies split into segments—head, thorax, abdomen—but none of this is visible on an adult, intact barnacle. Most of its anatomy is held within a ring of calcium-carbonate plates, roughly conical, that protect the animal from predators, the pounding surf, and the desiccating nature of the sun. This is the part of a barnacle you’re most likely to see: its outer aegis, homologous to the shells of crabs and other crustaceans. Inside this cone is a tiny creature perched, rather improbably, on its head. Its back is to the bottom of the cone, and its limbs are pointed upward. What corresponds to the forehead of the barnacle is cemented to the substrate. Its six limbs, called cirri, are long and feathered and are used to sieve plankton from the water, bringing it down to the mouth to be eaten. As an infraclass, the 1,220 species of barnacles worldwide are known as Cirripedia, Latin for “curl-footed”.

The Pacific Northwest is home to twenty-nine of those species, including what is arguably the weirdest-looking of them all: the Gooseneck Barnacle (Pollicepes polymerus), anatine fixture of our rocky intertidal shore. The “neck” is more accurately known as a peduncle, and it acts as a holdfast, anchoring the creature to rocks, logs, boat hulls, etc.

If you’re thinking, “Hey, that thing really does look like a goose’s head, hanging off a rock,” then you might forgive the Welsh monk Giraldus Cambrensis’s error in judgment, made in 1188 in his natural history treatise Topographia Hiberniae, when he deduced that the barnacles were, in fact, baby geese. Over in Wales, there is another species of gooseneck barnacle, Lepas anserifera, which attaches to driftwood and other flotsam. Cambrensis saw a physical similarity between these barnacles and a local goose species, Branta leucopsis—a bit of a stretch, this was—and claimed that, since the goose had never been seen to nest in Europe, and since the barnacles were always found on branches as from a tree, the two were simply different forms of the same plant-like organism. (Keep in mind that this was long before bird migration had been figured out.) For a while people believed him, took his assertion that the geese were “neither flesh, nor born of flesh” to heart, and even went so far to deem B. leucopsis fit to eat on religious holidays when the consumption of meat was forbidden.