Two freshwater flatworms

The garden barrel is one place where some invertebrate activity is guaranteed any time of the year. Snails graze algae in the winter and Water Slaters, Asellus aquaticus, munch the decayed leaves. There are predators too: flatworms. These innocent looking, slug-like animals, covered in sticky mucus slither on the surfaces of leaves looking for prey. Today I found two species, a small, dark one, probably Dugesia lugubris (top) and a large white one, Dendrocoelum lacteum (bottom). Both species shown here have a pair of simple eye spots, other species have more eyespots.

The LED lights of the hand held microscope reflect on the water surface and bring out the colour of the branching gastrovascular system of Dendrocoelum lacteum. The white band in the middle of the body is the evertible pharynx, on one end of which is the mouth. Small organisms, including Water Slaters, are often prey of flatworms, and are subdued with the mucus and wrappen on the flexible bodies of the flatworm.

More information

Richard Fitter & Richard Manuel 1986 Collins field guide to Freshwater life. 

Helen Mellanby 1975 Animal life in freshwater life. Chapman & Hall.