Treasure of the month June: The lugworm

12 June 2020

The lugworm cavorts in the soil of 2020 and is our treasure of the month in June. 14 species of the sandworm family, to which the lugworms belong, are preserved in alcoholic solution in jars in our collection - including Arenicola marina, which is found in Germany (Fig. 4). As a builder of the mudflat floor, a single worm shifts about 25 kilograms of sand annually.

Anyone hiking in the North Sea or diving in the Baltic Sea will usually inevitably find small piles of sand - the remains of the 30 to 40 centimeter long lugworms. They prove it: Our treasure of the month ensures that the tidal flat floor remains a living habitat. Without its voracious existence, the tidal flats would be characterized by overfertilization and oxygen depletion. In the North Sea alone, an average of 40 specimens live per square meter. Their tireless efforts not only enrich the soil with oxygen, but also break down dead plant material at the same time. Collectively, they eat the entire sand of the North Sea tidal flats, up to 20 centimeters deep, and then excrete it again. This corresponds to a total area of around 9,000 square kilometers - about the size of the island of Cyprus.

Lugworms live in a tube shaped like a U. The walls are covered with mucus. The walls are lined with slime to keep their home from collapsing. Inside, they lie mostly horizontally and use tiny, wave-like movements to keep water flowing steadily through their home. Meanwhile, the sand filters nutrients - bacteria, plant debris or algae - out of the water. At the same time, the lugworm can absorb oxygen with the help of its gill tufts. With its head attached to the vertical passage of the living tube, it eats the sand, which then trickles down. This creates holes on the surface, which lugworms know as feeding funnels.

After about 45 minutes of feasting on sand, the worm then has to go into reverse: Tail first, it crawls up the excretor tube of its burrow and, once at the surface, leaves behind the familiar piles of spaghetti. When it comes to pushing sandline, our treasure of the month usually puts its life on the line: birds lie in wait for the fat prey hiding under the pile of lugworm dung. They peck away as soon as new piles of sand form on the mudflats. If the worm is caught, it can shed up to two centimeters of its body and quickly burrow back into its tube.

In the LIB collection, we have both lugworm specimens and varnish films that accurately depict its home. In the Annelida (annelid) collection we have more than 200 specimens from a total of 14 species of the sandworm family, to which the lugworms belong, preserved in alcoholic solution in jars. Our specimens are mainly from the mudflats around Helgoland and other German islands and are up to 128 years old. More than 600 varnish films are stored in our mineralogy, which are mainly used for teaching or as reference in research. They depict an exact soil profile and can record its composition for posterity.

Further information

Special exhibition "Watt erleben - Wattboden verstehen" 
Annelida