Eisen, 1878
Type species Pachydrilus beumeri Michaelsen, 1886
Number of species larger than 80. At least two species known from fresh waters of NWE:
Mesenchytraeus armatus (Levinsen, 1884)
Mesenchytraeus sanguineus Nielsen and Christensen, 1959
The total number of species recorded from soil in NWE reaches 20. Many of them can presumably occur in shallow freshwater, too; however, their proper identification needs a study of internal anatomy.
Description
Large or medium-sized worms, mostly white or yellow but some species darker. Chaetae sigmoid, simple-pointed, with nodulus, arranged in fan-like bundles; their number per bundle variable, usually larger in ventral bundles. Head pore on apex of prostomium. Male pores in XII, clitellum from XII to XIII-XV. Internal characters: Coelomocytes of one kind only, usually spindle-shaped and granulated. No appendages on digestive tube. Dorsal blood vessel reaching backward at least to XIII. Nephridia consisting mainly of a bunch of nephridial canal, without any interstitial tissue. Spermathecae of various shape, usually with glands at their ectal pore in 4/5. Vas deferens usually terminating with atrium. Egg sac present, extending backwards through several segments. Similar to genus Cernosvitoviella by their fan-like bundles of sigmoid, nodulate chaetae; differing from it in larger size, presence of egg sac reaching for several segments rearward the clitellum, and many other details of internal anatomy.
Burrowing in sediment.
Distribution
Holarctic.
Ecology
In soil and freshwater, particularly in cooler habitats.
Reproduction
Sexual only, with eggs laid in cocoons.
Literature
Eisen, 1878: 67; Levinsen, 1884: 230; Michaelsen, 1886: 294; Nielsen and Christensen, 1959: 30-32; Kasprzak, 1986: 90-91.