Abstract
Two new species of nematodes associated with crabs are described from New Caledonia. Gammarinema scyllae sp. n. from the gill chambers of Scylla serrata (Forsskål) is characterised by 3-4 mm long body, small outer labial and cephalic sensilla, distinct ocelli, short straight spicules and sub-cylindrical tail. Monhystrium mangrovi sp. n. from the gill chambers and body cavity of mangrove crab Neosarmatium sp. is characterised by 1-1.4 mm long body; outer labial sensilla longer than cephalic sensilla, amphid located at level with posterior stoma chamber, denticles in posterior stoma chamber and five pairs of genital papilla on tail. Phylogenetic relationships of two new species and other nematodes from the family Monhysteridae are analysed based on 18S and partial 28S rDNA sequences.