title: Temporal stability of parasite distribution and genetic variability values of Contracaecum osculatum sp. D and C. osculatum sp. E (Nematoda: Anisakidae) from fish of the Ross Sea (Antarctica).
abstract: The Ross Sea, Eastern Antarctica, is considered a "pristine ecosystem" and a biodiversity "hotspot" scarcely impacted by humans. The sibling species Contracaecum osculatum sp. D and C. osculatum sp. E are anisakid parasites embedded in the natural Antarctic marine ecosystem. Aims of this study were to: identify the larvae of C. osculatum (s.l.) recovered in fish hosts during the XXVII Italian Expedition to Antarctica (2011-2012); perform a comparative analysis of the contemporary parasitic load and genetic variability estimates of C. osculatum sp. D and C. osculatum sp. E with respect to samples collected during the expedition of 1993-1994; to provide ecological data on these parasites. 200 fish specimens (Chionodraco hamatus, Trematomus bernacchii, Trematomus hansoni, Trematomus newnesi) were analysed for Contracaecum sp. larvae, identified at species level by allozyme diagnostic markers and sequences analysis of the mtDNA cox2 gene. Statistically significant differences were found between the occurrence of C. osculatum sp. D and C. osculatum sp. E in different fish species. C. osculatum sp. E was more prevalent in T. bernacchii; while, a higher percentage of C. osculatum sp. D occurred in Ch. hamatus and T. hansoni. The two species also showed differences in the host infection site: C. osculatum sp. D showed higher percentage of infection in the fish liver. High genetic variability values at both nuclear and mitochondrial level were found in the two species in both sampling periods. The parasitic infection levels by C. osculatum sp. D and sp. E and their estimates of genetic variability showed no statistically significant variation over a temporal scale (2012 versus 1994). This suggests that the low habitat disturbance of the Antarctic region permits the maintenance of stable ecosystem trophic webs, which contributes to the maintenance of a large populations of anisakid nematodes with high genetic variability.
authors.affiliation: Department of Public Health and Infectious Diseases, Section of Parasitology, Sapienza University of Rome, P.le Aldo Moro 5, 00185 Rome, Italy.
authors.forename: Simonetta
authors.initials: S
authors.lastname: Mattiucci
authors.affiliation: Department of Public Health and Infectious Diseases, Section of Parasitology, Sapienza University of Rome, P.le Aldo Moro 5, 00185 Rome, Italy; Department of Ecological and Biological Sciences, Tuscia University, Viterbo, 01100, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Cipriani
authors.affiliation: Department of Public Health and Infectious Diseases, Section of Parasitology, Sapienza University of Rome, P.le Aldo Moro 5, 00185 Rome, Italy; Department of Ecological and Biological Sciences, Tuscia University, Viterbo, 01100, Italy.
authors.forename: Michela
authors.initials: M
authors.lastname: Paoletti
authors.affiliation: Department of Public Health and Infectious Diseases, Section of Parasitology, Sapienza University of Rome, P.le Aldo Moro 5, 00185 Rome, Italy.
authors.forename: Valentina
authors.initials: V
authors.lastname: Nardi
authors.affiliation: Istituto Zooprofilattico Sperimentale del Mezzogiorno, Via Salute, 2, 80055, Portici (Naples), Italy.
authors.forename: Mario
authors.initials: M
authors.lastname: Santoro
authors.affiliation: Department of Ecological and Biological Sciences, Tuscia University, Viterbo, 01100, Italy.
authors.forename: Bruno
authors.initials: B
authors.lastname: Bellisario
authors.affiliation: Department of Ecological and Biological Sciences, Tuscia University, Viterbo, 01100, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Nascetti
keywords: Allozymes; Anisakids; Antarctic fish; Contracaecum osculatum s.l.; Genetic variability; Marine food-web; Parasitic infections; mtDNA cox2