Ever Wondered?

How Do Barnacles Attach to Whales?

It’s hard out there for a symbiotic barnacle, but somehow they find a way

March 22, 2010

For a hungry barnacle, the rim of a baleen whale’s nostril isn’t a terrible place to be. When the whale swims through a cloud of plankton for a meal, the barnacle — which also feeds on the tiny, floating organisms — gets free table service. All it has to do is extend its feathery, filtering arm and wait.

Barnacles regularly colonize the skin of filter-feeding whales, and they often do so in huge numbers — one humpback whale, for instance, can host almost 1,000 pounds of barnacles. (That may sound burdensome, but relative to a humpback’s nearly 80,000-pound body, it’s about as much extra weight as summer clothing on a human being.)

Whale-bound barnacles aren’t just regular barnacles with wanderlust; they’re different species, most of them unique to the brand of whale they piggyback on. The barnacle Coronula diadema lives only on humpback whale skin, for example, while gray whales host one called Cryptolepas rhachianecti.¹

So how does a barnacle get onto a whale in the first place? Like other stationary marine invertebrates, barnacles begin their lives as larvae — tiny, shell-less swimmers that find a place to settle and develop into the sturdy barnacles we know. Easy enough when all you want to stick to is an immobile rock, but a whale?

“We don’t really know how they’re doing it,” said John Zardus, a marine biologist at The Citadel military college in Charleston, South Carolina. For the last six years, Zardus has studied the barnacles that live on various marine animals, including whales. “These microscopic larvae that are swimming around in this huge ocean — how do they find a whale? … It just seems preposterous, actually.”

Research on whale barnacles is scarce, according to Zardus, because they’re not the easiest beasts to get a hold of. The larvae are small and difficult to distinguish from other kinds of barnacle larvae, and the adults are so deeply embedded in the skin of their hosts that they have to be carved out, flesh and all. Zardus only gets samples to study when there’s a dead, stranded whale he can take a chunk from — but if he takes too long to get to it, the barnacles will be dead, too.

Marine biologists speculate that the barnacles reproduce during the whales’ breeding season, when the whales mill around in warm, shallow waters rather than moving through the open ocean. If that’s true, Zardus said, the whales would swim in a thick soup of larvae; each barnacle parent can release anywhere from 10,000 to 20,000 spawn, and they survive for several weeks in the water. When a whale does swim by, research suggests, the drifting larvae pick up a chemical signal that tells them to hop on.²

There’s plenty of space to squat on a whale, but barnacles are picky. They like spots where the flow of water is consistent, Zardus explained, like the head or the fins. So instead of settling wherever they land, the larvae use their front antennae to “walk” around the whale in search of prime real estate. And that’s no easy stroll: if a barnacle larva were the size of a person, a whale would be over 20 miles long. Luckily, the larvae produce a sticky cement that keeps them from falling off into the ocean during their trek.

“They may walk over the whale for a long time until they find the place they’re looking for,” Zardus said. “It’s not random.”

Once they’re satisfied with their location, the barnacles dig in — literally. As they mature into adults, they form tube-shaped cavities in their shells that actually draw in prongs of growing whale skin. The result is an attachment as firmly rooted as the most pernicious weed.

whalebarnaclescloseup
Coronula diadema barnacles embedded in a piece of humpback whale skin. [Credit: Adolf Seilacher, Yale University Department of Geology and Geophysics.]

The barnacle-whale relationship is generally considered to be obligate commensalism — a type of symbiosis where one species benefits, and the other isn’t affected either way. Still, it’s possible that too many barnacles could cause drag, Zardus said, or invite infection if they penetrate too deeply into the whale’s flesh. On the other hand, it’s been suggested that for male humpbacks, who fight over females by ramming and slapping at each other, a sharp barnacle coating may be helpful as a set of brass knuckles.


¹ The uniqueness of whale barnacle species means that whaling and whale habitat loss put not only the whales at risk, but also their hitchhiking companions, said Dan Rittschof, a Duke University marine biologist who has studied barnacles for over 30 years.

“If you’re an endangered whale,” Rittschof said, “then everything that lives on you, like a barnacle, is also endangered.”

² In 2005, in one of the rare laboratory experiments on whale barnacles, Japanese environmental scientists Yasuyuki Nogata and Kiyotaka Matsumura placed Coronula diadema larvae in Petri dishes of seawater — some alone, and some with a slice of whale skin. The larvae by themselves floated around until they died, but the ones near the whale skin started settling on the surface of the dish.

“The settlement cue appears to be released [into the water] from the tissue of the host whale,” the researchers wrote in a March 2006 paper in Biology Letters. The exact nature of the chemical cue, however, remains unknown.

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About the Author

Mara Grunbaum studied English and environmental science at NYU. Before returning to New York, she worked for several years as a freelance reporter in Portland, Oregon, where she wrote about local politics, poverty and social justice. As a science reporter, she’s most interested in biology, ecology and most anything having to do with the ocean. You can also read her blog or follow her on Twitter.

Discussion

31 Comments

eightlegg says:

Amazing and intriguing!

Brad says:

Do the barnacles itch? They look like they would irritate or itch the whale…

We got the largest barnacles I’ve ever seen at our lobster dock in Gloucester yesterday. they were HUGE

I never knew there was a fleshy animal living inside the razor sharp barnacle enclosures. In many of the pictures I included a quarter so you can get an idea of the scale of these humongous creatures. I also got some pretty decent video of the creatures opening their enclosures and the organism alive coming in and out of it. It’s straight out of Aliens.

You can see the pics I took of it here-

http://goodmorninggloucester.wordpress.com/2010/06/23/the-largest-barnacles-ive-ever-seen-in-all-my-years-at-the-dock/

sam says:

i want to feel the barnacles and i want to take one home

andy says:

Do grey whales use barnacles as a defense against orca attacks?

KC says:

This is so disgusting…

Jolene L. says:

Can orcas get them? I don’t remember them being so familiar on that species skin or body.

Alicia Valencia Erb says:

Totally random Google search after I saw “crust” on these poor whales, so thanks for the great article. Wish there was a way to help these lovely creatures get these hitchhhikers off their backs.

Sue S says:

I found this most interesting…thank you. Just goes to show, what looks so uncomfortable to we humans isn’t necessarily so for these gentle giants of the oceans.

Andi Watson says:

This is horrible! We need to help these whales and get these things OUT of their flesh.

GG says:

Seeing this stuff drives me crazy and makes me itch all over! I’d love to remove each one from that whale :/

Grub says:

Completely agree with the people who are totally repulsed by these carpets of barnacles completely covering a whale’s head, belly, or whatever its huge back flipper is called. If you do an IMAGE search of “whale barnacles,” you will see such huge infestations that you want to sandblast the poor whale where it is covered, or use some kind of giant squeegee to scrape off layers of barnacles and roll them up like round hay bales and let them fall to the ocean floor! I spent hours looking at pictures and creasing about whale barnacles and lice yesterday, and I couldn’t sleep last night because I was tortured by the feeling that I must have head lice! I agree these things are gross and horrible, and think that people who find them beautiful are weird! The sight of these shells embedded into whale skin by the billions makes my skin crawl! One picture showed a sea turtle so covered in barnacles that he drowned because they were so heavy and hampered his swimming so much that he could not come up for air. Horrible, evil crustaceans…..Ugggh! Apparently they cause no harm to the whales, but they look like the must itch terribly. Like those pods in “Aliens,” I just want to blow-torch them!

on the fence says:

I know that it is a symbiotic relationship between endangered whales and the barnacles, but the thought that the barnacles could settle in places that could cause great harm to the whales causes me great distress, it definately seems like something out of science fiction!

Goob says:

Those poor whales! I hate those barnacles. And what if they attach to the whales balls?

cierra says:

why would they do that to the poor innocent whales?????????

cierra says:

i am so glad i am not a whale

ABanana says:

I can’t believe it! Why would those barnacles want to irritate the poor endangered animal!

M.E.M says:

Ouch, I wouldn’t want to be any kind of sea creature. -shudder-

Agreed says:

@Grub
Lol, you described this so thoroughly that I could roll over and die laughing. In a word I think what you and many feel is called “disgust”. Yeah they can be pretty unsettling… they are like aliens. Ick. Although, it might be worth it to try not to be too grossed out because they have their value; between moderating the amount of small organisms in the ocean, to being delicacies on a plate. Just like wasps and bees and other creatures (particularly the small ones in big numbers, like ants) they have some disadvantage attached to their presence.

Mitch says:

Poor whale? The whales don’t care people. Sheesh. Read the article

WoWz says:

Wow, they kinda remind me of pimples…..Does that HURT?

Glenda says:

Mitch, this article DID say that too many barnacles can be a problem.

I am bothered by these insidious opportunistic barnacles, too. It must be in our genetic make up to clean away things like this. I always killed off the red fox (?) that followed Sonic the Hedgehog -lol. If I could, I would burn the meaty bit of the barnacle, and, hopefully, it would fall off the poor sea creatures.

B. says:

How can baby whales snuggle up to their parents without getting lacerated by the razor-sharp edges of these horrible alien parasites?

I don’t understand how anyone can think that whales don’t mind having these things burrowing into their skin for the whole of their lives. Whales are mammals with mammal skin like ours, so of course it must hurt them terribly, as it would any mammal. Which daft scientist decided that “whales don’t mind it”? This is not commensalism, it is horrific parasitism.

animal says:

It’s funny how everyone’s getting upset at the barnacles ‘harming’ the whales, yet no one bats an eyelid at the poor barnacle larvae that are literally dying as a result of not clinging onto whales. It’s very selfish and hyprocritcal to be concerned for the welfare of one animal (the cute one) and not of another (the nasty one).

Xenoplasm says:

Wow guys, maybe you should read or at the bare minimum /think/ before posting some of these ridiculous opinions.

1) These are not parasites. They are not harming their hosts, and they are a valid part of the open ocean ecosystem, just like the whales. Whale skin is very, very thick, and to the whales, these are little more than tattoos.

2) Sandblasting a whale or otherwise scooping out these barnacles would result in the death or severe injury of the whale. I have a whale barnacle shell sitting on my desk; it’s about two inches deep, and the very top of the shell is the only part that is exposed. It would be more like pulling teeth.

Opinions based on how you feel are merely inadequate here. People harm wildlife and ecosystems every minute because they act based on how they feel or because they are anthropomorphizing the animals/plants involved. Whales are utterly unlike humans, and the only thing we really have in common is a degree of intelligence and endothermy. Whale skin is very thick and the barnacles are not causing harm.

Finally, I’m an ecology major who is close to completing his degree. I have the knowledge and soon I will have the authority to tell most of you that you are /idiots/ with harmful opinions, so good luck disproving my assertions.

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weeble says:

@Xenoplasm: nobody has authority to provide opinion and facts. The authority is within you – do not let the disease of “must be an expert”, or “must have a degree” group think deter from offering facts.

Keith Jones says:

There are actually 3 animals involved in this commensal relationship. I disagree with the author as to there being no benefit to the whale from the barnacles. A second parasite lives on the whales, called whale lice. These small crab like creatures find refuge from being washed off the moving whale in the calm area between clusters of barnacles. The whale lice cling to the whale skin with two pincers similar to crab claws, but much smaller. These claws are extremely sharp and strong.

The whale benefits from having the whale lice ONLY when the whale has an injury. The whale lice move to the wound and eat the wounded flesh, thus keeping that healing flesh from getting infected. This is a 3 way beneficial relationship with all three benefiting from one of the others.

At least that is my personal theory about whale barnacles.

Also, I believe the author meant to say that gray whales may have up to 1000 pounds of barnacles on them, not humpbacks.

Davy Jones says:

I have barnacles on my hat XD

Mynj says:

You’re free willy

pattie lowe says:

This, an occurrence in nature isn’t open to judgement. Unsightly or not isn’t important, as it’s not thought to be secondary to human interference, simply “normal flora” on whales, I say let it be. Consequently, human interference in nature, even with best intentions has proved decimating. ie, the introduction of various insect and wildlife species to areas that isn’t their natural dwelling in order to control something else. The thought we should have a part of regulating, or changing mother nature is a mistake, so what the occurrence is unsightly?

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