BDeed's picture


Observed: 26th March 2011 By: BDeed
Merseyside BioBankThe Wildlife Trust for Lancashire, Manchester and
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Another barnacle, direction towards a decent guide would be appreciated!

Species interactions

No interactions present.


Mike Kendall's picture

difficult to tell

To identify most barnacles its necessary to see the opercular plates that close the aperture of the shell. A photograph is best taken square on.

Secondly, an idea of size would be helpful; this looks like a big barnacle, is that correct?

It looks as if the barnacles that once surrounded it have been lost and I can't see any evidence of a calcarious base.
If there was no calcarious base its probable that this was Semibalanus. Hope that helps.

Mike Kendall

BDeed's picture

It was quite large, not so

It was quite large, not so much as the smoother one i have pictured elsewhere. There were a few dotted around up to about 1.5cm though most were about 1cm.

Is the shape of the plates no use as a guide at all? (other than the number of them)

Mike Kendall's picture


The only plates that are helpful for the balanids and chthamalids are the scutal and tergal opercular plates. Barnacles tend to live in a matrix of other barnacles and get pushed and shoved around as they and their competitirs and so their other plates deform to meet the direction of the pressure. For example a 6 month old S.balanoides might be no more than a couple of millimetres tall if living in isolation but could be 5x that height if packed at a density >20 per cm2.
There are other barnacles where the form of the plates and the shape of the animal is very helpful.

The other feature that can be very helpful is the colour and pattern of the tergoscutal flaps,the tissue between the opercular plates. When exposed to air a barnacle can be persuaded to show these by splashing it with seawater ...sometimes.

Mike Kendall