Hypodontolaimus minus sp. nov. and Bolbolaimus distalamphidus sp. nov., Nematodes from the Yellow Sea, Including Phylogenetic Analyses Within Chromadoridae and Microlaimoidea

Two new species from the Yellow Sea, Hypodontolaimus minus sp. nov. and Bolbolaimus distalamphidus sp. nov., are described in this study. Hypodontolaimus minus sp. nov. is characterized by a relatively small body length, a cuticle with two longitudinal lateral differentiations connected with transverse bars, four files of sublateral somatic setae, a pharynx with an anterior and posterior bulb, L-shaped spicules, a slightly swollen proximal end, a distal end tapered with a posterior pointed hook, and a gubernaculum with dorsal caudal apophysis. Bolbolaimus distalamphidus sp. nov. is characterized by a relatively small body size, a strongly annulated cuticle, six short outer labial sensilla and four long cephalic setae, an amphideal fovea unispiral oval that is far from the anterior end, slightly curved spicules, gubernaculum with anterior-pointed apophysis, and a conical tail. Phylogenetic analyses within the family Chromadoridae and the superfamily Microlaimoidea based on combined rDNA sequences confirmed the placement of Hypodontolaimus minus sp. nov. and Bolbolaimus distalamphidus sp. nov. The subfamily of Chromadorinae is shown as a monophyletic clade, the genera of subfamily Hypodontolaiminae are shown as a paraphyletic group, and the genus of Ptycholaimellus shows high intraspecific diversity. The placement of genera Aponema and Molgolaimus within the superfamily Microlaimoidea is discussed based on combined rDNA sequences.