How do barnacles cement themselves to rocks?

Barnacles start life as larvae or ‘cyprids’ that swim around freely in the water. These cyprids must attach themselves to a hard substrate in order to complete the transition to adult life. When the cyprid finds an appropriate hard substrate to settle on it starts to attach itself using a ‘cement’.

A cyprid larva
Illustration: Jo Taylor / Source: Museum Victoria

The cement is released through the tips of the antennules (the first of two pairs of antennae). The cement is produced in glands at the base of the antennules, passes through ducts running up the centre of the antennule, and is released through the tip. The glands are regenerated and remain active throughout life. As the barnacle grows, the cement glands increase in size and become more complex. The broad base of the barnacles (where they are attached to the rock or substrate) continually develop secondary cement pores close to the growing margin, from which concentric rings of cement are released. The cement, which provides strong adhesion, is released as a clear liquid that hardens into an opaque, rubbery solid. It is composed of ‘quinone-tanned proteins’.

So a barnacle larva finds a nice-looking place to call its home, lands head-first and releases cement out of its antennules. It then spends its life stuck to the ground, flapping its legs about in a ‘hand-stand’ position!

Barnacles attached to a rock
Photographer: Rudie Kuiter / Source: Aquatic Photographics

Rocks are not the only places where barnacles settle. They also end up on wharf pilings and on the underside of boats. Many barnacles on a boat’s hull will slow it down and add considerably to the fuel bill because of the drag. Nautical engineers and chemists have developed anti-fouling paints that deter barnacle cyprids from settling. The poisonous chemicals in these paints, copper or tributyl-tin (TBT), leach into the water and do more than kill the barnacles – they are toxic to many other marine animals, and the use of TBT has been banned for small boats in harbours in many countries.

Comments (34)

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joel 24 April, 2009 17:15
hi i was just wondering about this rock what i found 3 days ago. 2 day later these people came to my school to talk to the calss about rocks so i asked them about it and they said it must be peace of plastic or pumus rock because the said pumum rock is the only rock in the world that floats in water and was pritty shocked because the rock that i found floated to.
tim 22 October, 2009 12:19
hi. may i know if there have been any applications done using barnacle glue or has barnacle glue been used for any commercial purposes? thank u
Discovery Centre 23 October, 2009 13:44

Hi Tim - thanks for your question which I've referred to the Museum's Collection Manager for Marine Invertebrates. We'll get back to you soon wih a response! 

Discovery Centre 3 November, 2009 12:25

Hi Tim! Thanks for your interesting enquiry, which we referred to our Principal Curator, Marine Biology. There are no studies to his knowledge about application of barnacle glue but he did think it sounded like a very good research project for someone!

uncle normy 19 May, 2015 01:26
Found article on gizmag about barnacle adhesion research. For future reference.
matt 4 January, 2011 11:03
what backround information could be about barnacles?
Discovery Centre 6 January, 2011 11:07
Hi Matt, for further information about barnacles, you should look at the link to the right under related resources. You could also purchase the new book on Barnacles published by Museum Victoria. The Marine Education Society of Australia Life on Australian Shores website also has a good section on barnacles.
Jessica Wurzbacher 5 February, 2011 00:55
Hello, Can barnacles reattach if removed/disrupted from their initial settlement spot?
Discovery Centre 16 February, 2011 11:48
Hi Jessica, barnacles cannot reattach if dislodged.
Emma 7 March, 2011 17:17
hi, was just wanting to ask why barnacles are usually all clustered together? How do they choose which place is a good stop to grow into an adult on?
Discovery Centre 5 May, 2011 16:37

Hi Emma,

The following information is taken from 'Barnacles' by Gary C.B. Poore and Anna Syme;

Most common barnacles are hermaphrodites, having both male and female reproductive systems. A barnacle will therefore fertilise a neighbour and in turn be fertilised by a neighbour...Being unable to move as an adult adds extra importance in the larva’s ability to settle onto a surface close to other barnacles of the same species in order to be able to breed. This immobility helps explain why all barnacles live in colonies of numerous individuals often touching each other.

.....the (larva) chooses a place to settle, such as a rocky shore. The (larva) not only detects chemicals emitted from adults of its own species, it responds to signals from the shore itself – such as tidal level, wave exposure and roughness – which ensures that it locates a suitable place for the adult to live. ...Barnacles may live for up to ten years.

Ron Carle 12 March, 2012 10:33
When barnacles attache themselves to a painted steel surface, do they damage / displace the paint?
Discovery Centre 15 March, 2012 16:47

Hi Ron,
Because of the way barnacles grow and attach to substrates they can foul steel structures. This is called 'calcareous (hard) fouling'. The process of removing this can cause damage to painted surfaces and subsequent damage to the steel by salt-water corrosion.

kiki 15 October, 2012 10:28
hi i would like to know how barnacles regulate meaning how do they respond to their environment and also how do they get rid of metabolic waste
Discovery Centre 21 October, 2012 11:41

Thanks for your question about barnacles – perhaps you could look at the reference mentioned above on page 9 for the first part of your question.  Barnacles have many receptors including eyes and are aware of their environments – such environmental factors as light and the chemical nature of the water surrounding them, and also the presence of other barnacles, are clearly the basis of their responses and reactions.   They have a quite complex nervous system.

So far as removal of metabolic waste is concerned you might like to look at An introduction to the biology of British littoral barnacles See the section on “Excretion” on pages 11-12.  Apparently there are glands on either side of the foregut and the main excretory product is ammonia.  This paper also has detail of the nervous system of barnacles too.

Victoria Kirby 11 November, 2012 07:56
Do you have any references for this?
matthew 16 January, 2013 01:55
How do Barnacles move?
Discovery Centre 22 January, 2013 10:38

Hi Matthew,

With the exception of their limbs, which move in order to assist in their feeding, barnacles are unable to move in a locomotory sense as adults, so once a barnacle chooses a place to settle, it attaches itself permanently.

In the information above there is a sketch of a larva, which is the mobile stage of their development - barnacles start life as larvae or ‘cyprids’ that swim around freely in the water, as also stated above.

Student 23 January, 2013 05:50
Do you think there is any relationship between surface roughness and choice of attachment site? Is there any preference for their attachment sites? Thanks!
Discovery Centre 28 January, 2013 11:19

Hi Jo,

For further information about barnacles, you should look at the link to the The Marine Education Society of Australia Life on Australian Shores website which has a good section on barnacles and their behaviour.

Roy 15 June, 2013 01:06
Hi Would barnacles be able to release cement on a substrate that has low voltage current?
Jessica 21 May, 2014 19:46
Thanks for the awesome information. I'm doing a report on the Barnacle for my Year 11 Biology. I was wonder what was the "cement" is? I can't seem to find any other information on the cement. Thanks you !
Discovery Centre 24 May, 2014 11:48
Hi Jessica - we have had some research done on this, and we've emailed you some information that we hope helps
Chris 30 October, 2014 07:32
How to protect boats from barnacles attachment? Is there a coating, or just chemicals in the painting, as far as I know, except for hazardous copper based compounds, Medetomidine?
Ron Fellows 5 May, 2015 09:59
I have an ancient "Mediterranean Pot" that is covered with barnacles inside and out. Said to be from a shipwreck, there is little to identify the pot. Some of the barnacles have come off and there is no paint below. Could the barnacles attachment disolve any paint if it was there?
Danielle 18 June, 2015 19:48
hi i am doing a report for my biology class and i would like to know how the the Chamaesipho columna Barnacle digest its food and what enzymes and hormones help assist the process of digestion also how does it reproduce? i cant seem to find any helpful information
Russell Thompson 26 October, 2015 20:50
Hi, i found an interest piece of timber in the sea with barnacles attached. If i keep it out of the water i assume they will die and smell? is there a process to kill them but to keep there structure intact and attached and remove any smell?
Rintu Das 5 January, 2016 23:42
How to maintain Barnacles in Lab.
Carteryan 3 March, 2016 04:02
how do barnacles attach to boats??!!
Pete 22 July, 2016 02:51
Are there any appreciable differences between barnacles that adhere to a stationary object (wharf pile, rock, etc.) and ones that adhere to moving objects (ships)?
jo fisher 24 July, 2016 00:03
I would like to make a resin or glue that is nontoxic to all life and is the strongest in the world one that dries underwater and can be used in automobiles and patent it so the numbers of people who want to see that it would be able
Student 25 September, 2016 11:51
Thank you for this very good general summary. The phrase "quinone-tanned proteins" was the keyword that allowed me to find much more and detailed sources through the Google and the research databases. I wouldn't know where to start otherwise. Also, open questions/comments and several researched replies with specific sources, this is very brave and generous. I hope everyone appreciates how valuable this is. (Other readers: Look left; there's a whole archive!)
Cynthia Ferrell 25 March, 2017 11:47
I cleaned up lots of trash on the beach today & much of it was covered in living barnacles. I knew they would surely die if I threw them away with the trash so I picked them off one by one and put them on some seaweed. It says above they cannot reattach. What will happen to them?
Discovery Centre 2 April, 2017 11:24

Hi Cynthia

It appears that the statement above may need to be re-assessed as there is evidence that barnacles can re-attach and this has been studied.  There is evidence in the New Scientist of March 18 1971 titled “Why scraping ships’ bottoms is frustrating work”. You can search for this on the internet.

Also re-attachment has been studied in reports like this one. Some of your barnacles may die but some could possibly re-attach to other surfaces, if they are available.  The lifespan of such barnacles is not so great which is another factor to consider also.

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