Description and molecular characterization of Geraldius jejuensis n. sp. (Nematoda: Chambersiellidae) from Korea.

A new species of the genus Geraldius isolated from the wood of a dead black pine tree is characterized using morphological data and molecular DNA barcodes. Geraldius jejuensis n. sp. is characterized by its lateral fields with two incisures; lip region conoid to rounded and continuous with body; hemizonid and excretory pore located posterior to nerve ring; excretory pore opening just at the beginning of hemizonid or within the contour of hemizonid; vulva a transverse slit in ventral view; opening in a depression, creating a circular profile in lateral view; rectum 1.4 to 1.7 times longer than anal body diameter; phasmids located 55.0 to 78.5 μm from anal opening; tail elongated, 146.0 to 177.0 μm long; gubernaculum 27.0 to 33.5 μm long, caudal papillae arrangement of seven pairs pre-cloacal, two adcloacal, and six post-cloacal; and three additional midventral papillae on anterior cloacal lip. The new species was compared with the three known species of the genus, including G. bakeri, G. galapagoensis and G. inserrai. The phylogenetic relationships among species were reconstructed using 18S-rRNA and 28S-rRNA gene sequences. Inferences from both genes corroborate the close morphological relationships between Geraldius and Diastolaimus.