title: Genetic relationships among Anisakis species (Nematoda: Anisakidae) inferred from mitochondrial cox2 sequences, and comparison with allozyme data.
abstract: The genetic relationships among 9 taxa of Anisakis Dujardin, 1845 (A. simplex (sensu stricto), A. pegreffii, A. simplex C., A. typica, A. ziphidarum, A. physeteris, A. brevispiculata, A. paggiae, and Anisakis sp.) were inferred from sequence analysis (629 bp) of the mitochondrial cox2 gene. Genetic divergence among the considered taxa, estimated by p-distance, ranged from p = 0.055, between sibling species of the A. simplex complex, to p = 0.12, between morphologically differentiated species, i.e., A. ziphidarum and A. typica. The highest level was detected when comparing A. physeteris, A. brevispiculata, and A. paggiae versus A. simplex complex (on average p = 0.13) or versus A. typica (on average p = 0.14). Sequence data from the newly identified Anisakis sp. poorly aligned with other Anisakis species but was most similar to A. ziphidarum (p = 0.08). Phylogenetic analyses based upon Parsimony and Bayesian Inference, as well as phenetic analysis based upon Neighbor-Joining p-distance values, generated similar tree topologies, each well supported at major nodes. All analyses delineated two main claides, the first encompassing A. physeteris, A. brevispiculata, and A. paggiae as a sister group to all the remaining species, and the second comprising the species of the A. simplex complex (A. simplex (s.s.), A. pegreffii and A. simplex C), A. typica, A. ziphidarum, and Anisakis sp. In general, mtDNA-based tree topologies showed high congruence with those generated from nuclear data sets (19 enzyme-loci) and with morphological data delineating adult and larval stages of the Anisakis spp.; however, precise positioning of A. typica and A. ziphidarum remain poorly resolved, though they consistently clustered in the same clade as Anisakis sp. and the A. simplex complex. Comparison of anisakid data with those currently available for their cetacean-definitive hosts suggests parallelism between host and parasite phylogenetic tree topologies.
authors.affiliation: Department of Public Health Sciences, Section of Parasitology, University of Rome La Sapienza, 00185 Rome, Italy.
authors.forename: Alice
authors.initials: A
authors.lastname: Valentini
authors.forename: Simonetta
authors.initials: S
authors.lastname: Mattiucci
authors.forename: Paola
authors.initials: P
authors.lastname: Bondanelli
authors.forename: Stephen C
authors.initials: SC
authors.lastname: Webb
authors.forename: Antonio A
authors.initials: AA
authors.lastname: Mignucci-Giannone
authors.forename: Marlene M
authors.initials: MM
authors.lastname: Colom-Llavina
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Nascetti
mesh_terms: D000818:Animals; D017129:Anisakiasis / Q000469:parasitology / Q000662:veterinary*; D017163:Anisakis / Q000145:classification* / Q000201:enzymology / Q000235:genetics*; D001483:Base Sequence; D002591:Cetacea / Q000469:parasitology; D003062:Codon / Q000235:genetics; D017931:DNA Primers / Q000737:chemistry; D004272:DNA, Mitochondrial / Q000737:chemistry; D003576:Electron Transport Complex IV / Q000235:genetics*; D014644:Genetic Variation; D006790:Host-Parasite Interactions; D008969:Molecular Sequence Data; D010802:Phylogeny; D016133:Polymerase Chain Reaction / Q000662:veterinary; D016415:Sequence Alignment / Q000662:veterinary; D013045:Species Specificity
chemical_list: D003062:Codon; D017931:DNA Primers; D004272:DNA, Mitochondrial; D003576:Electron Transport Complex IV