A new species of Ascarophis (Nematoda,Cystidicolidae) from the stomach of the marine scorpaeniform fish Hoplichthys citrinus from a seamount off the Chesterfield Islands,New Caledonia

A new species of parasitic nematode, Ascarophis (Similascarophis) richeri sp. nov. (Cystidicolidae), is described from the stomach of the marine scorpaeniform fish Hoplichthys citrinus Gilbert (Hoplichthyidae) (prevalence 19%, intensity 1–8 nematodes per fish) collected in the region of the Chesterfield Islands (Coral Sea, west of New Caledonia) in October 2005. The new species, studied using both light and scanning electron microscopy, is characterized mainly by the structure of the mouth (highly reduced pseudolabia, high pseudolabial terminal projections, no submedian labia, well-developed, bilobed sublabia), bifurcate deirids, the length of the spicules (663–729 μm and 105–108 μm) and the presence of filaments on both egg poles (2–5 on each). Similascarophis Muñoz, González et George-Nascimento, 2004 is considered a subgenus of Ascarophis van Beneden, 1871 to accommodate the species characterized by highly reduced pseudolabia. Presence of the new species in fish from Seamount Nova (Lord Howe Rise) but not from the Chesterfield plateau suggests that it is endemic to this seamount, a case already encountered for many benthic invertebrates.