Where they overlap and exist together they compete for space on the rock. In the UK we see the northern limit to the Chthamalus range and the southern limit of Semibalanus. Semibalanus, a northern species does better in cooler, wetter conditions. Chthamalus, a southern, warm water species, is tolerant of high temperatures and desiccation. Much research has been done on the principle of Competitive Exclusion with regard to the two species Chthamalus and Semibalanus. In Scotland they have been seen to cross-fertilise in the winter to release larva in the spring when there is a peak formation of diatoms in the plankton. 4 unequal shell plates and a species found underneath stones in the lower shore may also be on Laminaria holdfasts. It tends to live in the middle shore region of rocky shores.

It is thought that the shell plates are not as tough as those of Chthamalus and Semibalanus and this is why it is not found on wave-exposed shores. Also unlike other UK barnacles it has a tolerance of silty water and lower salanity. Unlike other barnacles it never seems to stop breeding (it is a cross-breeding hermaphrodite species) and this has resulted in a massive spread across north-west Europe. How strange andĮlminius modestus is a 4 shell-plated species that arrived here from Australasia, in the 1940's. Organ then surrenders to the way of all flesh and withers awayĪnd the males turn into females for next season. The Spring bloom of phytoplankton (which they feed on).

(the season not the tide) when they are released to coincide with To 8000 eggs and the females retain the larvae until next Spring The males copulate with the females fertilizing up Its length up to human proportions we are talking about roughlyĢ0 metres). Of a male organ of monstrous proportions. Indeed it would but for the male barnacle's possession You might thinkīeing glued down and surrounded by armour plating would render Separate sexes who must copulate to reproduce. Probably the commonest species (certainly around Dale Fort in Other small animals like the small winkle ( Melarhaphe neritoides).Ībove: Chthalamalus left, Semibalanus, right.

The shells of dead barnacles make favourable microhabitats for It is for the rest of its life (which might be as long as 12 years) It then grows the familiar plates and stays where This causes glue glands to rupture and the animal Has found a good spot it stands on its front end ('head')Īnd in an outburst of barnacly joi de vive bashes its headĮnd on the rock. Cracks and crevices are attractiveīut even better is the presence of other barnacles. The young barnacle wanders about on the shore lookingįor a suitable place to attach. Barnacles start lifeĪs a planktonic larvae which settle out on the shore after about Sets up a current over the gills for respiration and the muscularĬontractions serve to circulate the animal's haemolymph ('blood')įor like the tin man they have no heart. Modified legs which sweep through the water catching food (planktonĪnd detritus) from the water. They are filterįeeders and those feathery things sticking out of the top are If you could see them at high water (or in a tank)Īre actually very dynamic when covered by the sea. Up and waiting for the tide to come back in so they do not appear You usually see them at low water when they're closed There is a lot more to them than that howeverĪnd you will discover more if you read on:īarnacles are crustaceans, relatives of shrimps, crabs and Slippery seashore and give you a nasty graze on the elbow or knee

Rocky Shores | Rocky Shore Creatures Acorn Barnaclesīarnacles are the sharp little chaps that help you grip on the

Acorn barnacle