''Dendrocoelum lacteum,'' the milk-white planarian, is a freshwater

planarian Planarians (triclads) are free-living flatworms of the class Turbellaria, order Tricladida, which includes hundreds of species, found in freshwater, marine, and terrestrial habitats.pp 3., "Planarians (the popular name for the group as a whole ...

found in lakes and running waters in

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

, being the most widespread freshwater planarian in this continent.

Description

Mature specimens of ''D. lacteum'' measure between 12 and 25 mm in length and up to 6 mm in width. The body is completely white, although the presence of food in the intestine may give it a temporary different color. The head is narrower than the rest of the body and has a blunt end. There are two short blunt projections laterally to the anterior end that form tentacles. There is also a ventral subterminal sucker that is more evident during locomotion. The eyes are seen as two dorsal black dots wide apart right in front of the constriction that separates the head from the body. The body margins often have a frilled appearance.

Distribution and Ecology

''Dendrocoelum lacteum'' is widely distributed across Europe in all sorts of freshwater bodies. It is usually found under submerged rocks or dead leaves on the margin of the water bodies. The diet of ''D. lacteum'' consists of smaller invertebrates found in the same habitat. The main component of its diet seems to be freshwater

isopod Isopoda is an Order (biology), order of crustaceans. Members of this group are called isopods and include both Aquatic animal, aquatic species and Terrestrial animal, terrestrial species such as woodlice. All have rigid, segmented exoskeletons ...

s of the genus ''

Asellus ''Asellus'' is a genus of isopod crustaceans in the family Asellidae. Species ''Asellus'' is divided into three subgenera which contain the following species: ''Asellus (Asellus)'' Geoffroy, 1762 * ''Asellus amamiensis'' Matsumoto, 1961 * ''As ...

'' and their presence in a water body appear to be essential for the occurrence of the planarian. Other ingested invertebrates include

amphipod Amphipoda () is an order of malacostracan crustaceans with no carapace and generally with laterally compressed bodies. Amphipods () range in size from and are mostly detritivores or scavengers. There are more than 10,700 amphipod species cur ...

s of the genus ''

Gammarus ''Gammarus'' is an amphipod crustacean genus in the family Gammaridae. It contains more than 200 described species, making it one of the most species-rich genera of crustaceans. Different species have different optimal conditions, particularly ...

'' and, less frequently, freshwater

oligochaete Oligochaeta () is a subclass of soft-bodied animals in the phylum Annelida, which is made up of many types of aquatic and terrestrial worms, including all of the various earthworms. Specifically, oligochaetes comprise the terrestrial megadril ...

s. Differently from freshwater planarians of the families

Planariidae Planariidae is a family of freshwater planarians. The type genus is '' Planaria'' Müller, 1776.Ball IR: A contribution to the phylogeny and biogeography of the freshwater triclads (Platyhelminthes: Turbellaria). Biology of the Turbellaria (Ed ...

and

Dugesiidae Dugesiidae is a family of freshwater planarians distributed worldwide (except Antarctica). The type genus is ''Dugesia ''Dugesia'' is a genus of freshwater planarians in the family Dugesiidae triclads and the type genus of this family. Thes ...

, ''D. lacteum'' does not feed on freshwater

snail A snail is a shelled gastropod. The name is most often applied to land snails, terrestrial molluscs, terrestrial pulmonate gastropod molluscs. However, the common name ''snail'' is also used for most of the members of the molluscan class Gas ...

s, which allows it to coexist with other planarian species without much food competition.

References

{{Taxonbar, from=Q902024 Dendrocoelidae