Two new species of free-living marine nematodes of Adoncholaimus Filipjev, 1918 (Oncholaimida: Oncholaimidae: Adoncholaiminae) from Hokkaido, northern Japan, with a key to species and discussion of the genus

Abstract

Two new species of free-living marine nematodes,Adoncholaimus daikokuensissp. nov. andA. pseudofervidussp. nov., from the coastal area of northern Japan, are described and illustrated.Adoncholaimus daikokuensissp. nov. is similar to five congeners,A. derjugini,A. punctatus,A. oxyuroides,A. squaluscomb. nov. andA. filicaudacomb. nov. in the absence of a gubernaculum, but differs in the absence of a ventral swelling on tail, spicule length and buccal cavity length.Adoncholaimus pseudofervidussp. nov. is similar toA. fervidusin having large body size, short tail, similar positions of the excretory pore and nerve ring, short spicules, arrangement of subventral setae in posterior region of body in males, and a single pair of terminal pores of the Demanian system surrounded by small gland cells in females.Adoncholaimus pseudofervidussp. nov. differs fromA. fervidusin having smaller, more anteriorly located amphids, longer buccal cavity, absence of gubernaculum in the male, and a different position of the terminal pores in the female. Partial sequences of the mitochondrial cytochromecoxidase subunit I gene (309-337 bp) of the new species are provided for identification based on the DNA barcoding method.Metoncholaimoidesis proposed as a junior synonym ofAdoncholaimus. The new diagnosis ofAdoncholaimusand a key to species are provided.Adoncholaimus squaluscomb. nov.,Adoncholaimus filicaudacomb. nov., andAdmirandus papillatuscomb. nov. are proposed.