How Barnacles Baffled Biologists for So Long

PBS Eons host Kallie Moore explains how the elusive barnacle baffled biologists for many years despite their immense ubiquity in maritime environments,

They’re found  in virtually all marine environments,   stubbornly attached to any surfaces they can find  – from rocks and boats to whales and turtles. They may not look like much, but beneath that  shell lies an evolutionary mystery – one that  stumped the biggest names in natural  history for over a hundred years.

Included in this list of scientists was Charles Darwin, who set out to study this symbiotic creature for a year and found himself spending almost eight years on the project. No matter how he dedicated himself, however, he remained woefully confounded by the creature’s classification.

Some of the most influential biologists of their  day grappled with the challenge of working out   what they actually are and where they fit in the  tree of life, only to be proved totally wrong. Others were almost broken by the  attempt – including Charles Darwin,   who embarked on an eight-year-long  personal side-quest to figure them out. By year six, he wrote to a friend, “I hate  a Barnacle as no man ever did before”.

The barnacle eluded specific scientific classification due to its similarities, to both mollusks and crustaceans. Previous scientists had put them in the mollusk category. Another scientist, however, William Thompson, subsequently believed them to be crustaceans. Darwin, despite his frustrations with the creatures, found evidence that agreed with Thompson’s analysis.

Despite being so frustrated by  these creatures that he found himself wishing that they never  existed – a feeling familiar to   many graduate students – Darwin did  eventually see the end of his work. His detailed analysis of modern and extinct   species is still important to  the study of barnacles today. He helped confirm Thompson’s radical reclassification of barnacles as a branch of the crustacean family tree,  and they’ve stayed there ever since.