Dirk Drawlans’ Wild Animals: How Barnacles Invade Our Seas

Barnacles are among the most unusual creatures that can wash up on our shores. Many people are puzzled when they find a set of rubber stems with strange pictures on top on a piece of wood or a bottle in the tide line. The term “foreigners” has already been used.

The view of the animals is really amazing. Their larvae are fairly normal little creatures, free-swimming, drifting with the currents and trying to attach to anything they encounter. This is usually driftwood, but it could also be plastic waste or even another animal, such as a sea turtle or seal. They stick together with a self-produced cement-like substance.

Once attached, the animal begins to grow into its bizarre adult form. It has a brown stem with yellow contents, and can reach a length of 5 to 25 cm (more than half a meter exceptionally). From an anatomical point of view, it is strange that the torso protrudes into the head. The head and rest of the barnacle’s body are located on top, protected by a structure of five grey-blue triangular plates a few centimeters long. There are often twelve arms protruding from the whole, which together like a scoop net filter everything edible from the water. The movable trunk helps animals orient themselves and makes eating easier.

Contrary to what their name suggests, barnacles are not mussels. They are small crustaceans related to barnacles: the white lumps on mussels and mussel beds that lobsters also live in. Because they can be taken on their raft over long distances, they are widespread. If they accidentally wash somewhere, they die immediately.

Although they reproduce sexually, that is, by fertilization, barnacles are hermaphrodites, both male and female at the same time. This is useful in the context of limited mobility. Animals are attached to the substrate and therefore cannot actively search for a mate. In such a case, evasion helps. Any specific person you meet is then guaranteed to be of the correct gender. Small colonies of barnacles often live on the substrate. The free-swimming larvae must be very numerous to achieve this. The animals then fertilize their neighbors and are fertilized by the neighbors.

We owe the “ducks” in the name to the limited biological knowledge and rich imagination of our ancestors. They saw barnacles and other geese in their area in the winter, but never found their eggs or young – geese breed this far north, but they didn’t know it. Since barnacles of barnacles have little to no soft shaft, they imagined the “mussels” to produce goslings. Only from the end of the 16th century, after Dutch whalers discovered Spitsbergen and other northern islands and saw geese breeding there, did people realize that they were wrong. But the name was kept.