Three new species of the order Enoplida (Nematoda) from the Yellow Sea, China

Three new free-living marine nematodes belong to the order Enoplida from the Yellow Sea, China are described. The first new species, Halanonchus gracilis sp. nov. is characterized by inner labial sensilla papillose, outer labial setae and cephalic setae thick, with thin tips; oval amphideal fovea located posterior to buccal cavity; males possessing midventral row of 10–12 papilliform pharyngeal supplements and 13–15 unequal papilliform precloacal supplements; spicules almost straight, 0.85–1.0 cloacal body diameter long; gubernaculum rod-shaped. The main difference between the described species and other known species within the genus is that precloacal supplements are unequal, 6–7 posterior supplements smaller and closer, the rest 7–8 proximal supplements larger and far away. The genus Halanonchus is the first record from the Chinese sea area. The second new species, Micoletzkyia oxycephalata sp. nov. is characterized by very sharp-pointed anterior part of body, paired spicules unequal and precloacal supplement situated anterior to proximal end of spicules. This new species can be easily distinguished from all other known species of Micoletzkyia by outstanding body shape, unequal spicules, stick shaped gubernaculum without apophysis, and the position of precloacal supplement. The third new species, Wieseria zhangi sp. nov. is characterized by slender body with a clavate tail; large amphideal fovea oblong, double contour with a manubrium basally, situated posterior to cephalic setae; spicules short, slightly arcuated, not cephalated proximally, without internal stripe and ventral alae; gubernaculum rodlike, without apophysis; a short midventral spine positioned 11–12 µm anterior to the cloaca. Updated keys to species of three genera Halanonchus, Micoletzkyia, and Wieseria are also given.