Barnacle revenge


Low tide on a barnacle and seaweed covered beach

I took my daughter to a local beach yesterday. We arrived in the sun-dappled parking lot as a Pat Benatar’s ‘Hit Me With Your Best Shot‘ finished playing on the radio. Only a light sprinkling of parked cars were in the lot and no one was on the path down to the water, a pleasant consequence of being there on a weekday. A short set of concrete stairs lead us out onto a mostly rubble beach broken up with a few patches of sand exposed by the low tide.

After we crossed the slippery seaweed and barnacle encrusted rocks, I showed my daughter how to look under rocks for crabs. The first one she picked up skittered out of her hand and vanished under more rocks. The hunt was on. She eagerly flipped more rocks, finding more crabs in the process. Then she looked closely at the rock in her hand. Like a miniature mountain range, a cluster of empty barnacle houses remained adhered to the surface. Why the barnacles weren’t there I don’t know. My daughter didn’t question their absence, instead she examined the structures then crushed the empty exoskeletons.

Most barnacles are sessile filter feeders, raking the water with their arms when the tide is in and closing up shop when the tide leaves them exposed to air. In most marine environments, barnacles can be found glued to any hard surface from whales to ship hulls to rocks. Due to their lack of mobility, barnacles have developed the longest penis relative to their body size of any animal (picture here). Probably for other reasons, Charles Darwin focused his research efforts on these marine invertebrates from 1846 to 1854.

For 7 years Darwin looked at the anatomy of different barnacle species. At the time barnacles were grouped with clams and mussels in the mollusc family (which is where I would have assumed they fit). Darwin went on to compare how barnacles develop with other families. He discovered that barnacles share common features with crustaceans like crabs, lobsters and shrimp. Barnacles were moved from the molluscan to the crustacean family and Darwin was awarded a medal.

Barnacles have a two stage life-cycle starting out as larvae free swimming for 10 to 45 days. In that time, they have to make the biggest decision in their lives – where to set up their permanent home. If other barnacles of the same species are already living somewhere, often they take it as a sign of a good place to live, which is why they can be found in such high numbers. On the beach, with each step I took, I could feel barnacles crunching under my sandals making me feel like Godzilla crushing the homes of those in my way.

Barnacles have had their revenge on me, hitting me with their best shot. As a kid, I loved to wade out on rocky beaches to see the marine life and to swim. I always went barefoot making crossing the ubiquitous barnacle colonies risky. I’ve cut myself on barnacles many times and the cuts plus salt water always stung. Unfortunately, I’ve now introduced my daughter to that family tradition. She left the beach with her first barnacle scraped knee – fortunately, only a minor cut.