Barnacles have a way of clinging to you the moment you utter their name. The consonants crackle in the mouth echoing through the the mind’s antechambers before wedging themselves like gravel in the folds of our thoughts.
Phonetically and syntactically, “barnacles” is in perfect harmony. Once uttered, it sticks to mouth and mind with the same irrepressible strength that it grips hulls, shells and whalehide.
This steadfast attachment follows from decidedly rootless beginnings. Barnacles begin life as drifting zooplankton feeding in the water column. After several molts, they enter the cyprid stage – still swimming, but no longer feeding, their sole purpose to find a place to settle.
Barnacles are sessile as adults, but their transformation hinges on this moment of commitment. The cyprid glues its head to its host’s surface using a proprietary cement evolved once upon a time in their lineage and nowhere else in nature.
Many marine animal glues (like those from mussels) use dopa (3,4-dihydroxyphenylalanine), a sticky amino acid derivative. Barnacle cement doesn’t rely on dopa. Instead, it’s rich in lysine and other amino acids that form a different bonding complex. Barnacles use oxidative enzymes (peroxidases) to create covalent cross-links between proteins, locking them into an insoluble, rock-hard matrix.
The cyprid has antennal appendages tipped with temporary adhesive pad, letting it cling mechanically while still able to “walk” or reposition. Before pouring its cement down, a lipid-rich primer is secreted to displace water, drying the spot in situ. The protein binder then cross-links on this primed surface forming an unbreakable bond capable of resisting high-velocity currents.
Once those cross-links form, there’s no going back. The cured adhesive doesn’t soften or re-dissolve in seawater. Permanently attached, the cyprid metamophoses into a barnacle, its swimming legs turning into feathery cirri that sweep plankton (including the occasional cyprid) and other detritus into its mouth as its mantle begins secreting the calcareous plates we equate with the animal.
Until the 1830s scientists thought barnacles were mollusks because of their shells, but William Vaughan Thompson’s discovery of their free‑swimming larval stage proved they are crustacean.
Barnacles in the Feed
A couple of days ago my social media feed filled with clips of people prying barnacles from sea turtles and whales. The implication was that barnacles are pests that need to be removed. The reality is more nuanced.
The NOAA Marine Turtle and Biology and Assessment Program and the Archie Carr Center for Sea Turtle Research agree: barnacle removal is only necessary in limited cases. In healthy tutles, barnacle loads are incidental. In debilitated turtles, heavy barnacle cover is a symptom rather than a cause of poor health; often because they aren’t swimming enough to prevent settlement. Barnacle proliferation is thus Nature’s way of culling the herd.
For those who view humans as ecological actors rather than external observers, removal is warranted only when barnacles burrow into the skin, block eyes or nostrils or impede swimming. Improper removal can in fact damage the shell and cause infection , so rehabilitators often leave benign barnacles alone.
On whales, the relationship is even more complicated. Humpbacks host two species of barnacles who as plankton settle on the whale’s tail riding through rich feeding waters.
Researchers at the Marine Education and Research Society describe the relationship as symbiotic: barnacles gain a feeding platform while the whales get fitted with the equivalent of brass knuckles adding weight to tail slaps during fights.
A Scienceline report characterizes whale–barnacle interactions as obligate commensalism; barnacles feed as whales swim rarely causing harm. Only excessive growth can increase drag or invite infection.
Chaos and Classification
Not long ago I read Lulu Miller’s Why Fish Don’t Exist. Miller recounts the life of fish taxonomist David Starr Jordan (a moral paradox in his own right) and explores how humans impose order on the natural world in ways that often collapse under scrutiny.
His life’s work, “fish”, turned out to be taxonomically meaningless. As a category it is what biologists call a paraphyletic group – a catch-all for species that look similar or live in similar habitats but don’t include all the descendants of their last common ancestor.
“Fish”, as a taxonomic class, is the equivalent of concocting a category of mountain dwelling animals we call mish. This category would include carnivorous mammals, hoofed ungulates, arachnids, reptiles and birds.
In evolutionary terms, “Fish” isn’t a true category at all. All vertebrates emerged from jawless fishes over 500 million years ago, and from them came sharks, rays, bony fishes, and eventually the lobe-finned fishes that walked onto land and became amphibians, reptiles, birds, and mammals.
If “fish” were a proper evolutionary group, you’d be one too. The word survives not because it is biologically accurate, but because it’s sticky. It is a manufactured label that is no more coherent than calling every mountain-dwelling creature a mish. That’s why lungfish are more closely related to cows than to salmon.
Darwin’s Barnacle Years
Charles Darwin knew the power of barnacles to unsettle categories. After returning from the Beagle voyage he planned to spend a month describing an unusual, shell‑less barnacle he had collected off Chile.
Darwin found that previous work on barnacles was sloppy and decided to reclassify the entire group . He corresponded with museums, dissected specimens under lamplight, and eventually produced a four‑volume monograph. The project consumed eight years of his life and nearly dragged him under.
In the process he observed variations within species: differences in shell thickness, cirri length and reproductive structures. He discovered dwarf males that existed solely as sperm sacs attached to hermaphroditic females.
These observations provided empirical support for his emerging theory of natural selection by showing how small variations could accumulate and how organs could be repurposed or lost. Darwin later said that without his barnacle years he would not have noticed the variability that underpins evolution.
How to Feel About Barnacles
So how should we square off with a barnacle? This plankton cum calcerous nub, infrequently and accidentally a cannibal, that lives commensally with its hosts for the most part, symbiotically at one extreme and parasitically at the other.
I believe neutrality is merited.
The barnacle defies our usual moral categories: it’s neither purely beneficial nor harmful, neither fully independent nor completely dependent. It forces us to confront our need to categorize and judge, existing in the spaces between our definitions through pure adaptive flexibility rather than ideological commitment.
Here lies a deeper parallel between word and creature: while the word “barnacles” adheres stubbornly to our consciousness once spoken, the living barnacle teaches us about productive detachment, the ability to respond to conditions without being wedded to predetermined outcomes. The creature’s cement may be permanent, but its moral stance remains fluid, pragmatic, contextual.
In our polarized world, perhaps we need this barnacle-like neutrality: not the paralysis of indecision, but the wisdom of detachment from fixed positions. The barnacle succeeds not by choosing sides but by reading environmental cues and responding proportionally.
But this raises a crucial question: how does pragmatic neutrality contend with rigid dogma? The key is recognizing that neutrality toward outcomes doesn’t require neutrality toward process. A barnacle may be indifferent to which surface it colonizes, but it is completely committed to its survival.
Similarly, moral pragmatism can remain detached from specific political positions while being utterly attached to the conditions that make pragmatism possible: open discourse, evidence-based reasoning, the ability to change course when circumstances shift.
Against a truly dogmatic nemesis, the pragmatist’s advantage isn’t superior ideology but superior adaptability. Dogma is brittle; it breaks when reality doesn’t conform. Pragmatism bends, persists, and ultimately outlasts rigid systems by remaining responsive to what actually works rather than what should theoretically work; whether we understand the reasons or notd.
The barnacle’s greatest lesson may be that true pragmatism requires letting go of moral attachment to specific outcomes, maintaining the flexibility to be beneficial, neutral, or even parasitic as circumstances demand, guided not by ideology but by what the situation actually requires. The barnacle’s cement may be permanent, but its capacity to find new surfaces and new ways of being remains infinite.
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