Barnacles
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40 free Barnacles trivia questions with answers — trivia quiz, new questions added Oct 2026.
Barnacles look like the dullest things on the shore: small pale cones that sit on a rock and do nothing. In fact they are among the strangest animals in the sea. They build their own armour, glue themselves in place for life with a cement engineers still envy, and manage to eat, breathe and breed without ever moving house. This quiz collects the fun facts about barnacles that people go looking for: what kind of animal a barnacle really is, how it feeds and finds a mate, which creatures it hitches rides on, and why sailors have cursed it for centuries. There are questions on the barnacles people eat, the parasitic kinds that take over their hosts, the famous naturalist who gave them years of his life, and the medieval belief that tied them to a bird. A handful cover the barnacles of film, television and space exploration. It suits beachcombers, boat owners, students and anyone who has wondered what lives inside those sharp little shells. Every answer comes with a short explanation, so you finish knowing more than when you started.
30 of 40 questions with answers and explanations. Play the quiz
Q 01A rock barnacle spends its whole adult life glued upside down to the shore by which part of its body?
Its forehead
Its forehead is where the cement glands sit, at the base of the first pair of antennae. A larva picks the spot, glues itself down and never moves again.
Q 02A feeding barnacle combs food from the water with feathery cirri, which are modified versions of which body parts?
Legs
Legs are what a barnacle feeds with: six pairs of them, curled and fringed with hairs, sweep out through the top of the shell and rake food towards the mouth.
Q 03For its body size, a barnacle has the longest what of any known animal?
Penis
Penis length in barnacles can reach eight times the body length, the largest ratio of any known animal. It stretches out to fertilise neighbours cemented nearby.
Q 04Which Victorian naturalist spent eight years dissecting barnacles and then declared he hated them as no man ever had?
Charles Darwin
Charles Darwin's barnacle monographs won him the Royal Society's Royal Medal in 1853. He worked on them at home so intently that his young son assumed every father did the same.
Q 05Barnacles were classed as molluscs until their swimming larvae revealed that they belong to which animal group?
Crustaceans
Crustaceans is the right group, which makes barnacles cousins of shrimp and lobsters. John Vaughan Thompson showed it in 1830 by watching the free-swimming young settle and turn into adults.
Q 06Which ocean giant, famous for its long knobbly flippers, can carry as much as 450 kg of barnacles on its skin?
Humpback whale
Humpback whale skin suits one barnacle species so well that a single animal can carry 450 kg of them. The passengers feed for free as their host swims through the sea.
Q 07Goose barnacles called percebes, picked by hand from wave-battered rocks, are a costly delicacy in which two countries?
Spain and Portugal
Spain and Portugal prize percebes so highly that harvesters called percebeiros risk their lives on surf-pounded cliffs to gather them. The name comes from Latin words for thumb and foot.
Q 08Which Pirates of the Caribbean villain commands a barnacle-encrusted crew who slowly become part of their ship?
Davy Jones
Davy Jones captains the Flying Dutchman, whose cursed sailors grow shells and coral until the hull absorbs them. Bill Nighy played him through motion capture.
Q 09In the children's series Octonauts, the crew's leader Captain Barnacles is which kind of animal?
Polar bear
Polar bear Captain Barnacles is strong enough to lift a giant clam, yet one episode reveals that he is claustrophobic. His crewmates include Kwazii the cat and a penguin medic called Peso.
Q 10Barnacle geese were once thought to grow from barnacles because nobody in Europe saw them nest; where do they breed?
The Arctic
The Arctic is where barnacle geese raise their young each summer, far from the European shores where they winter. The word barnacle named the bird first and the shellfish only from the 1580s.
Q 11Barnacle Boy is the grumpy sidekick of which elderly superhero in SpongeBob SquarePants?
Mermaid Man
Mermaid Man and his partner were voiced by Ernest Borgnine and Tim Conway, who had starred together in the 1960s sitcom McHale's Navy. The pair send up the Batman TV series of the same decade.
Q 12The commonest barnacles, which grow their cone-shaped shells straight onto rock, are named after which tree nut?
Acorn
Acorn barnacles keep the same shell for life: the animal inside moults its skin as it grows, but the hard plates are never shed and simply gain new material.
Q 13A shore barnacle shuts the four movable plates of its door at which time, to keep from drying out?
Low tide
Q 21Barnacle cement inspired MIT researchers to make a medical paste that can do what within about 15 seconds?
Stop bleeding
To stop bleeding, the paste forms a tight seal on wet tissue, much as a barnacle grips a wave-washed rock. The animal's own fast-curing cement is among the most powerful natural glues known.
Q 22What is the sailors' term for the build-up of barnacles and weed that slows a ship's hull through the water?
Fouling
Fouling by barnacles can raise a ship's drag by as much as 60 percent and its fuel use by 40 percent, on a US Navy estimate. Some boaters call the culprits crusty foulers.
Q 23Before dry docks, crews beached a sailing ship and heaved it onto its side to scrape off barnacles, a job called what?
Careening
Low tide leaves shore barnacles in the open air, so they close up to hold in moisture. As the sea returns, the door reopens and the feeding limbs come out.
Q 14In the 18th century the Royal Navy began nailing thin sheets of which metal over hulls to keep barnacles off?
Copper
Copper sheathing was first fitted to a whole hull on the frigate HMS Alarm in 1761, chiefly to stop shipworm boring into the timbers. The metal's poison was also expected to slow barnacle growth.
Q 15The parasitic barnacle Sacculina sterilises which animals and makes the males behave like egg-carrying females?
Crabs
Crabs infected by Sacculina are taken over from within by root-like threads. The host stops breeding and instead tends the parasite's young, fanning them into the sea as if they were its own.
Q 16The giant barnacle picoroco is an essential ingredient of curanto, a pit-cooked seafood feast from which country?
Chile
Chile harvests the picoroco along its coast, where the barnacle grows as tall as 30 cm. In a curanto it is cooked over heated stones with clams, mussels, meat and potatoes.
Q 17Some scientists think a coat of barnacles helps certain baleen whales fight off bites from which ocean predator?
Orcas
Orcas may think twice about biting a flipper studded with sharp shells. Whales built to fight seem to carry the heaviest barnacle loads, while faster species that flee stay almost clean.
Q 18The Barnacle is a yellow parking enforcement device that attaches to which part of an offending car?
Windshield
Windshield suction holds the Barnacle in place and blocks the driver's view until the fine is paid. Students in Oklahoma beat it within days, using defoggers and credit cards.
Q 19Goose barnacles, unlike the cone-shaped kind that sit flat on rock, attach themselves to surfaces by means of what?
A fleshy stalk
A fleshy stalk anchors each goose barnacle, and in ocean-drifting species it can be more than half a metre long. It is also the part that diners eat.
Q 20The shell-less barnacle Anelasma feeds through root-like tendrils sunk into the flesh of which deep-sea hosts?
Sharks
Sharks such as lanternsharks and dogfish carry Anelasma half-buried in their skin. Its feeding limbs have shrunk to useless stubs, and it seems to stop its hosts from maturing sexually.
Careening takes its name from carina, the Latin for a keel. With the ship hauled over on a beach, each side of the bottom could be scraped and repaired in turn.
Q 24The giant barnacle of the northeast Pacific, Balanus nubilus, contains the largest known examples of what?
Muscle fibres
Muscle fibres bigger than any other animal's sit inside this barnacle, which is why laboratories use it to study how muscles work. Sea stars prey on it, and small octopuses shelter in its empty shells.
Q 25Which sea snails are among the commonest predators of barnacles, able to grind through the shell plates?
Whelks
Whelks such as the dog whelk can also prise the plates apart with a proboscis and finish a barnacle in about a day. Limpets and mussels are rivals for space on the rock, not predators.
Q 26Which sense, served by sensitive hairs on the limbs, appears to be the main one a barnacle relies on?
Touch
Touch does most of the work, but a barnacle also has three simple eyes that can tell light from dark. When a shadow falls across it, it stops feeding and snaps shut.
Q 27Barnacle Bill, named for its barnacle-like bumps, was the first Martian rock analysed by which small Pathfinder rover?
Sojourner
Sojourner took ten hours to analyse Barnacle Bill with its X-ray spectrometer on the third day of the mission. Early readings suggested a volcanic rock called andesite.
Q 28Believing barnacle geese grew from barnacles, not eggs, some medieval clergy ate them as fish during which season?
Lent
Lent was a meatless season, so a bird thought not to be born of flesh looked like a handy loophole. Gerald of Wales criticised Irish clergy for the habit in the 12th century.
Q 29Which actor played a seasick naval officer and six of his ancestors in the 1957 Ealing comedy Barnacle Bill?
Alec Guinness
Alec Guinness made the film only as a favour to its director and later called it wretched. It was the last of the Ealing comedies and was released in America as All at Sea.
Q 30The drinking song Barnacle Bill the Sailor was the recurring theme for which character in the first Popeye cartoon?
Bluto
Bluto stomped on screen to the tune in 1933, and Fleischer Studios came back to it two years later for a Popeye mock operetta called Beware of Barnacle Bill.