Buckleyella ornata n. sp. (Nematoda: Philometridae) from the abdominal cavity of the talang queenfish Scomberoides commersonnianus (Perciformes: Carangidae) off the northern coast of Australia

A new nematode species, Buckleyella ornata n. sp. (Philometridae), is described from female specimens found in the abdominal cavity (mesenteries) of the talang queenfish Scomberoides commersonnianus Lacepède (Carangidae, Perciformes) caught in Darwin Harbour, northern Australia. Based on light and scanning electron microscopical examination, the new species mainly differs from the only other congeneric species B. buckleyi Rasheed, 1963 in having a markedly shorter oesophagus (2.04–2.75 mm long), by the absence of a cephalic mound around the mouth aperture, by the presence of four submedian cephalic papillae of the inner circle, and by a somewhat different arrangement of cuticular ornamentations on the body surface. Three protruding oesophageal teeth and large, dome-shaped cephalic papillae of the external circle present in the smallest gravid female of B. ornata are atrophied in larger conspecific gravid females. Buckleyella ornata is the first known nominal species of a philometrid parasitizing carangid fishes in Australian waters.