The taxonomic status ofSkrjabinalius guevaraiGallego & Selva, 1979 (Nematoda: Pseudaliidae) and the synonymy ofSkrjabinaliusDelyamure, 1942 andHalocercusBaylis & Daubney, 1925

摘要

Within the cetacean lungworm family Pseudaliidae Raillet & Henry, 1909, the distinction between the two genera of the subfamily Halocercinae Delamure, 1952, i.e.HalocercusBaylis & Daubney, 1925 andSkrjabinaliusDelyamure, 1942, is principally based on the structure and shape of the male copulatory bursa. In species ofHalocercus, the bursa is unlobed, whereas in the two species included inSkrjabinalius,S. cryptocephalusDelyamure, 1942 andSkrjabinalius guevaraiGallego & Selva, 1979, the bursa is described as clearly lobed. During a parasitological analysis of cetaceans from the Spanish Mediterranean, we collected a number of specimens ofS. guevaraiwith variable levels of bursal lobulation, including individuals with unlobed bursae. Examination of voucher specimens of the type-species ofHalocercus,H. delphiniBaylis & Daubney, 1925, collected from cetaceans in the North-East Atlantic revealed the same variations in bursal shape, and the same arrangement of bursal rays and papillae. A morphometric comparison did not reveal substantial differences between both species. Moreover, Maximum Likelihood and Bayesian Inference analyses of the second internal transcribed spacer (ITS2) sequences of 11 specimens ofS. guevaraiand one ofH. delphinigrouped both species together, regardless of bursal shape, in a highly supported clade within the Pseudaliidae. Accordingly, we considerS. guevaraias a junior synonym ofH. delphini. The great variability found in bursal lobulation in the type-species ofHalocercusinvalidates the use of this trait as a genus-level diagnostic character and, therefore,Skrjabinaliusshould also be considered synonymous withHalocercus.