Four new and one known species of Belondiroidea (Dorylaimida: Nematoda) from Japan.

Four new and one known species of Belondiroidea Thorne, 1939 are reported from Japan. Axonchium mizukuboi sp. nov. has isthmus-like constriction between two parts of pharynx; rectangular pars refringens vaginae; spicules with thickened distal end; seven ventromedian supplements starting above the range of spicules and hemispheroid tail. Axonchium japonicum sp. nov. also has short isthmus-like structure between two parts of pharynx; triangular pars refringens vaginae; massive spicules with thickened distal tip and 9-10 ventromedian supplements. Dorylaimellus (D.) japonicus sp. nov. has 0.9-1.0 mm long body; poorly flanged odontophore; pharyngeal expansion 54-65% of neck length; 22-25 μm long, strongly ventrally arcuate spicules; four ventromedian supplements and elongate conoid tail with subacute terminus. Dorylaimellus (Axodorylaimellus) paracrassidens sp. nov. has 0.4-0.5 mm long body; slender odontostyle; pharyngeal expansion 48-57% of neck length; transverse vulva; long prerectum and short conoid tail. Axonchium amplicolle Cobb, 1920 is reported for the first time from Japan. [ABSTRACT FROM AUTHOR]