Metazoan parasite infection in the swordfish, Xiphias gladius, from the Mediterranean Sea and comparison with Atlantic populations: implications for its stock characterization.
Bottom Line: A stepwise Linear Discriminant Analysis of the individual fish examined showed a separation among three groups: one including fish from the Mediterranean Sea (CTS, STS, and IOS); one consisting of fish from the Central South (CS), Eastern Tropical (ET), and Equatorial (TEQ) Atlantic; and a third comprising the fish sampled from the North-West Atlantic (NW); the CN Atlantic sample was more similar to the first group rather than to the other Atlantic ones.Finally, H. corrugatum, A. simplex (s.s.), Rhadinorhynchus pristis, and Bolbosoma vasculosum were related to the fish from the North-West (NW) Atlantic area.These results indicate that some parasites, particularly Anisakis spp. larvae identified by genetic markers, could be used as "biological tags" and support the existence of a Mediterranean swordfish stock.
Affiliation: Department of Public Health and Infectious Diseases, Section of Parasitology, "Sapienza" University of Rome, P.le Aldo Moro, 5, 00185 Rome, Italy.Show MeSH
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Mentions: The parasitological survey was performed on 162 specimens of X. gladius from three different basin waters of the Mediterranean Sea, as reported in Table 1 and Figure 1. The fish were captured by pelagic long-line and trolling gear, between 2002 and 2004, from June to September. The lower-jaw fork length (LJFL) of the sampled specimens varied from 50 to 165 cm (Table 1), that corresponds, approximately, to 0- up to 4-year-old fish [9, 71]. Immediately after the capture, the LJFL was recorded from each fish on board the fishing vessels, and immediately, the swordfish body surface was visually inspected for the copepod Pennella spp.; the parasites found were removed from the fish muscle and stored in alcohol. The fish were then dissected on board, and the body visceral cavity was examined for the detection of the larval stage of anisakids and cestodes. These parasites were immediately stored in a frozen state or in alcohol. The stomach, intestine, and gills from each fish individual were removed, separated into plastic bags, numbered and stored in a frozen state at −20 °C, for further analysis. When on land, all the collected material was delivered, in a frozen state, to the Section of Parasitology (Department of Public Health and Infectious Diseases, Sapienza University of Rome) and stored there at −30 °C for the parasitological examination. Thus, conventional parasitological analysis was carried out on the gills, stomach, and intestine. All the metazoans were collected, counted, and preserved in 70% alcohol for the morphological identification, except for the larval anisakid nematodes, which were stored at −50 °C and then scored using multilocus allozyme electrophoresis analysis (MAE) for their species identification. MAE was used for the identification to the species level of 405 Anisakis spp. larvae, since they lack morphological diagnostic characters. The procedures used for the MAE are those previously detailed . The diagnostic allozyme loci so far listed between the species of Anisakis [46, 50, 52] were investigated: adenylate kinase (Adk-2, EC 126.96.36.199), leucine-alanine peptidase (PepC-1, PepC-2, EC 3.4.11), and leucine-leucine peptidase (PepB, EC 3.4.11). In total, 405 larvae from the Mediterranean samples were identified to the species level.Figure 1.
Affiliation: Department of Public Health and Infectious Diseases, Section of Parasitology, "Sapienza" University of Rome, P.le Aldo Moro, 5, 00185 Rome, Italy.