New species of Metadesmolaimus, Rhynchonema and Gairleanema (Nematoda) from the sandy beaches of the Sea of Japan.

Little is known about the diversity and systematics of nematodes from intertidal sands of the Sea of Japan (East Sea). Here, nematodes of the rare genus Gairleanema and two new species of the family Xyalidae are described and illustrated. Metadesmolaimus innii sp. nov. can be easily distinguished by the combination of a large conspicuous amphideal fovea and unequal long spicules (the right spicule is larger than the left one). Rhynchonema pulchrum sp. nov. can be easily distinguished from all known congeneric species in having a combination of the following features: the number of annulations from the anterior end to the anterior edge of the amphideal fovea (37-38 in males and 34 in females); amphideal fovea form and size (oval in males vs сircular in females); large spicules with proximal capitulum, gubernaculum with paddle-like apophysis and inflated precloacal annuli. Gairleanema arenosa sp. nov. is characterized by the combination of the following characters: the moderately long body (1445-1707μm), long setiform labial sensilla with bulbous swellings and thin cephalic setae; unispiral small amphidial fovea located at the posterior edge of the cephalic capsule, dorsal tooth, subventral onchia and small denticles; four-five pairs of mamilliform supplementary organs.