Genetic and morphological evidences for the existence of sibling species within Contracaecum rudolphii (Hartwich, 1964) (Nematoda: Anisakidae) in Australia

The aims of this study were to examine specimens of Contracaecum rudolphii from Australian hosts, both morphologically and genetically, based on the ITS-1 and ITS-2 sequence data, to provide a re-description for the species and to investigate the genetic make-up of this species in Australia. Morphological examination of adult specimens of C. rudolphii sensu lato Hartwich 1964 from two species of cormorants Phalacrocorax carbo and P. varius in Australia, showed that they can be divided into two distinct morphotypes. Distinction of C. rudolphii sensu lato was supported by characterisation of the ITS-1 and ITS-2 regions of rDNA which showed that they belong to two different genotypes, different from those occuring in the northern hemisphere and studied previously. Base-pair nucleotide differences of 0.9–2.2% and 1.1–6.8% for ITS-1 and ITS-2, respectively, have been detected among different genotypes of C. rudolphii sensu lato. Herein, the two new species have been designated as Contracaecum rudolphii D and Contracaecum rudolphii E.