Chaetonema cycloamphidum sp. nov. (Nematoda: Anoplostomatidae) from the Bohai Sea, China

A new species of free-living marine nematode belonging to genus Chaetonema is described from Tianjin coast along the Bohai Sea, China. Chaetonema cycloamphidum sp. nov. is characterized by its relatively smaller body size in the genus, narrow head with cephalic capsule, six outer labial setae unequal with four longer ones (3.8 head diameters) and two shorter ones (2 head diameters), amphidial fovea circular in males, buccal cavity cup-shaped without teeth, spicule arcuated with expanded proximal end and tapered distal end, gubernaculum plate-like with curved proximal end, a small ventral precloacal seta instead of precloacal supplement. The new species can easily be distinguished from its congeners by circular amphidial fovea, unequal outer labial setae and different shape of spicule and gubernaculum. Updated dichotomous key for the valid species of genus Chaetonema is given.