The genus Metateratocephalus contains several species of bacterivorous nematodes of which at least one species - M. crassidens, described by the Dutch nematologists de Man in 1880 - occurs in the Netherlands. They are small nematodes, usually smaller than half a millimetre, which occurs in soil as well as in fresh-water.
Remarkable is that the terrestrial specimens never exceed 0.4 mm in length whereas the aquatic individuals reach a length between 0.4 and 0.5 millimetre. Do they belong to one and the same species? Also remarkable is the long generation time for such a small nematode. Adult specimens are usually found in winter; their density is highest in January. Juveniles reach their highest density in March.
More pictures of Metateratocephalus:
(Click on the pictures for an enlargement, © Wageningen University & Research, Laboratory of Nematology/Pictures: Hanny van Megen)