A new cystidicolid nematode from Mullus surmuletus (Perciformes: Mullidae) from the western Mediterranean.

Ascarophis valentina n. sp. is described from Mullus surmuletus off the Valencian coast of Spain on the basis of both light and scanning electron microscopy. It can be distinguished from the other members of the genus by the length of the left (long) spicule of the males and by egg morphology. An updated grouping of the species of Ascarophis considered valid is provided with respect to these characters. The new species resembles Ascarophis capelanus, belonging to the group of species possessing eggs with a single polar knob with filaments, but is distinguished by the size of the body, the length of the esophagus (especially in relation to body length), the position of the vulva, and the size of the left spicule. The new species also shows substantial morphological differences compared with the 3 species, Ascarophis mullusi, Ascarophis upenei, and Ascarophis parupenei, previously described from mullid hosts.