Dead Man’s Fingers

Coral in Swedish waters

Most people associate corals with tropical waters. But did you know that there are corals here in Sweden too? Dead man’s fingers is a coral, often white or orange, that lives on rocky or stony seabeds along the Swedish west coast. It gets its peculiar name because it often grows with rounded, knobbly shoots. With a little imagination, it can look like a swollen, severed hand at the bottom of the sea.

Building a colony

You might think corals are plants, but they are actually animals. Dead man’s fingers are made up of a colony of tiny coral animals called polyps. Most colonies are either female or male, but there are also dead man’s finger colonies that produce both eggs and sperm. The coral grows by the polyps budding off. Each polyp in a dead man’s finger colony has its own mouth, and tiny arms around its mouth that they use to capture plankton to eat. When the coral is eating, all the polyps stick out, and the coral takes on a fuzzy appearance.

Reproduce in the winter

During autumn, dead man’s fingers are often inactive. They go into a kind of hibernation while their reproductive cells mature. The coral may then develop algal growth and look almost dead. Dead man’s fingers reproduce in winter, when the females release eggs and the males release sperm. The eggs are fertilised in the water, and when they hatch, a small larva emerges – which starts looking for a place to settle. When it finds a good spot, it grows and becomes a polyp, which starts to build its own colony. Dead man’s fingers grow best on rocks and stones, but also on other hard surfaces such as shipwrecks or the shell of a crab.