Description of Acuaria europaea n. sp. (Spirurida: Acuariidae) from Dendrocopos syriacus (Hemprich & Ehrenberg) and Oriolus oriolus (L.) (Aves) in Europe, with results of re-examination of related European species of Acuaria Bremser, 1811.

Acuaria europaea n. sp. is described from one Dendrocopos syriacus (Hemprich & Ehrenberg) (Piciformes: Picidae) (type-host) and three Oriolus oriolus (L.) (Passeriformes: Oriolidae) in Bulgaria (type-locality) and France. The new species is characterised by cordons extending slightly beyond the level of the anterior end of the glandular oesophagus, left spicule 297 µm long, right spicule 155 µm long, protruding vulvar region and strongly ventrally curved female tail. The male (holotype) and the female (allotype) of A. parorioli Chabaud & Petter, 1961 from O. oriolus are regarded as not being conspecific based on the differing morphology of their cordons; the female is identified as A. europaea n. sp. The type-material of Acuaria attenuata (Rudolphi, 1819) is redescribed. The species is characterised by a small and delicate body, cordons extending beyond the oesophago-intestinal junction and similar spicules in size and shape, 140 µm long. The only type-material of Acuaria anthuris (Rudolphi, 1819) available for examination consists of a male and a female (syntypes) from O. oriolus. The two specimens differ from one another by the relative lengths of their cordons and we consider them as belonging to two species. However, both type-specimens differ in their much shorter cordons from the species of Acuaria parasitising Corvidae. The present study reveals that the original description of A. anthuris has been based on heterogeneous material.