Wild Harris

Link to Rocky Shore Animals

Barnacles are extraordinary animals. Imagine living upside down in a box all your life, closing the lid when you wanted to sleep and waving your arms and legs around to catch food which happens to pass you by. This is the life of a barnacle! These crustaceans are related to crabs and lobsters, and like them begin life as a shrimp-like larva which are free-swimming in the sea with the other plankton. When they find a suitable hard surface, preferably already colonised by adult barnacles, they glue their head to the rock and grow a protective shell to surround their body. The top of the shell has tiny doors which allow the barnacle to feed. This it does by waving its fan-like legs in the water when the tide is in, catching small food morsels which it carries inside to its mouth. If you closely observe barnacles when they are covered by water you can easily see them in action. When the tide goes out they retreat inside their shell and close the doors tight, awaiting the next high tide. The hard shell protects them from predators and stops them from drying out, as well as preventing the sea from washing them off. Barnacles are very numerous in many places, particularly where the shore is not particularly sheltered, and can often dominate the rock so much that there is no room for seaweeds to grow.

(Photo: Paul Tyler) 

Barnacles as they are seen when the tide is out. Empty shells are where the animal has died or been eaten by a predator. 

Dogwelk on barnacles    (Photo: Paul Tyler)

The barnacle's deadliest enemy, a dogwhelk. When the tide returns it will go back to drill ing through the barnacle's shell and scooping out the animal inside. 

The sex life of a barnacle

Many, if not most, marine animals breed by releasing sperm and eggs into the water and hoping that they will fertilise each other (quite a few brown seaweeds use this method too). Barnacles, however, like other crustaceans, use internal fertilisation - that means the sperm have to be placed inside the body of the female. Since they can't leave their shell this poses a problem, how do you reach a female barnacle? The solution is is simple the barnacle has a penis that is 13 times the length of its body - making it the longest penis (compared to body size) in the animal kingdom! With this mighty organ the male can reach the doors of his neighbours' shells, and mate with any females that are within reach. 

by Paul Tyler

Link to  Rocky Shore Animals