Fig. 1

Localities and habitat of hydrothermal species. a Mid-Atlantic Ridge in North Atlantic Ocean; b hydrothermal vents (black triangles) along the Mid-Atlantic Ridge; c aggregation of mussels Bathymodiolus azoricus, habitat of most nematode species here described, Lucky Strike (by courtesy of A. Sagalevitch, V. Nishcheta and S. Galkin)