Tenuidraconema tongaense n. sp. (Nematoda: Draconematidae), a new free-living marine nematode from a seamount in the southwest Pacific Ocean

A new species of free-living marine draconematid nematode, Tenuidraconema tongaense n. sp., is described. This new species was collected from shallow subtidal dead corals and detritus from a seamount in a hydrothermal area off the Tonga Islands, southwest Pacific Ocean. Tenuidraconema tongaense n. sp. differs from the known species of the genus by the following combination of characters: longer body (1060-1265 μm), position of 12 cephalic adhesion tubes (anterior six cephalic adhesion tubes inserted on rostrum and posterior six adhesion tubes inserted on anterior body annule in male; all 12 cephalic adhesion tubes inserted on rostrum in female), number of posterior sublateral adhesion tubes (11 in male, 12 in female) and posterior subventral adhesion tubes (9-11 in male, 10-11 in female) with somatic setae intermingled between the two anteriormost sublateral adhesion tubes, longer spicule length (43-50 μm), and slender body (a = 41.1-48.6 in male and 29.4-35.1 in female). A pictorial key and a dichotomous identification key for males and females are provided for the species. A table comparing the major differential diagnostic characteristics of the species of Tenuidraconema is presented.