S. M. Adl
The enchytraeids, sometimes referred to as "potworms", are distributed globally and are common in
most soils. Enchytraeids are a family of earthworms (Oligochaeta: Annelida: Clitellata: Enchytraeidae)
where species lengths range from several hundred micrometres to 6 cm. Their internal anatomy is
similar to earthworms and easily described from live specimens at the microscope because the
epidermis and cuticle are usually transparent, although tissues are lightly pigmented in some.
At least 600 species are described from aquatic and terrestrial habitats mostly in Europe (Dash 1990).
However, most species remain to be described yet as many regions are still unsampled. For
identification, the monographs of Nielsen and Christensen (1959, 1961, 1963) describe many European
species. Since then, many new species of Enchytraeids have been described in the literature. An
identification key to genera, as well as a list of many North American species can be found in Dash
(1990). The genus Fridericia was reviewed recently (Schmelz 2003). The biology (Dash 1983) and
ecology of enchytraeids can be found in reviews (Lagerloef et al. 1989; Didden 1993; van Vliet 2000).
Enchytraeids are important to the food web and to organic matter decomposition in most soils. They
can even be found under snow and glacier ice, they are common in the sub-arctic where larger species
occur, and more abundant in soils rich in organic matter as well as in the forest floor. Their abundances