Goose Barnacles: reliving Darwin's view
After Darwin's return from the voyage on the Beagle, he dove into many areas of investigation, including a study of the barnacles.

On a recent exploration of the Florida Keys, I took along my Bancks microscope and spent a little time looking at goose barnacles, trying to experience the same view that Darwin may have had of these creatures.

In the Florida Keys sargassum weed often drifts in from the Sargasso Sea in the center of the North Atlantic. These little drifting islands of sea weed carry along a community of creatures, some are fairly mobile, and others are firmly attached to their wandering island. Among those that are more firmly attached are the goose barnacles (Lepas anatifera I think). They are attached to the sargassum by a flexible fleshy stalk called a "peduncle". Their bodies are protected inside a little box composed of 5 calcareous plates that are connected by soft tissue that acts as a hinge. The barnacle can open and close an opening in these plates and project its limbs for filter feeding.

I observed these barnacles attached to a variety of objects including sargassum, various floating seeds, plastic jugs and an onion. Thus it is hard to say where the barnacles joined the sargassum community, whether it was in the Sargassum Sea, or at some point on the sargassum's journey.

I collected a few stranded barnacles from the wrack line on the beach at Curry Hammock State Park and placed them in a small plastic tank. Some revived and started their feeding behavior of kicking their limbs (cirri) out the opening in their little box (capitulum), others did not seem to be recovering from their exposure on the beach. Their activity is wonderful to watch, these are fairly large barnacles and their 20 limbs are long. They flip their limbs out like a fisherman might quickly unfurl a net, they hold it for a moment, then sweep their limbs back into their protective case. Their motions are so smooth and graceful, as a cluster starts working it becomes a marvelous dance. It seems that they open in unison.

The above image is of a Goose Barnacle on sargassum weed. Click on the image for a labeled photo.
Observation Date: May 8, 2011
Observation Location: Curry Hammock State Park, Marathon, FL Map
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