Nielsen and Christensen, 1959
Type species Pachydrilus sphagnetorum Vejdovsky, 1878
Number of species 15. Two species known from fresh waters of NWE:
Cognettia glandulosa (Michaelsen, 1889b)
Cognettia sphagnetorum (Vejdovsky, 1878)
Some other species have been recorded from soil only in NWE.
Description
Small to medium-sized, slender, white or yellowish worms. Chaetae sigmoid, sharp-pointed, without nodulus, usually few in number. Head pore in 0/1. Male pores and beginning of clitellum either in XII or, in some species, more anteriorly. Internal characters: Pharyngeal glands often more than three pairs. Interstitial tissue in nephridia well developed. Spermatheca not connected with oesophagus; no diverticula; usually single gland at ectal pore in 4/5. Testes compact. Vasa deferentia long and narrow, confined to one segment. Penial bulbs present. Differing from Mesenchytraeus and Cernosvitoviella in sigmoid chaetae devoid of any nodulus; from Lumbricillus, revealing similar but usually more numerous chaetae, in compact testes not divided into bush-like lobes. Presence of regenerated anterior or/and posterior end, caused by architomy, is very common in the populations of both Cognettia glandulosa and Cognettia sphagnetorum but not in the other amphibious enchytraeids in NWE. Prevalence of bundles with three sigmoid, unnodulate chaetae is also most characteristic of these two species.
Burrowing in sediment.
Distribution
Holarctic, with most species in the Palaearctic.
Ecology
In soil and freshwater.
Reproduction
Mostly sexual, with eggs laid in cocoons. Asexual reproduction by architomy (fragmentation) prevailing in some species.
Literature
Roule, 1888: 1811-1813; Michaelsen, 1889b: 28; Nielsen and Christensen, 1959: 41-42; Kasprzak, 1986: 120.