Data collection
Tissue samples have been collected from the North Sea near Helgoland, the Iberian Atlantic coast near Sines/Setubal, the Gulf of Lion near Cassis and the Adriatic Sea near Rovinj, Croatia (Figure 1). Station data including detailed information concerning sampling date, latitude, longitude and water depth for every single investigated specimen have been recorded.
Genetic specimen analysis
DNA from a total of 160 specimens of the 4 selected populations (24 specimens from the Gulf of Lion, 42 specimens from the North Sea, 34 specimens from the Portuguese Atlantic coast and 30 specimens from the northern Adriatic Sea) was extracted. Mitochondrial DNA fragments were PCR-amplified with a set of previously optimized primers designed to target a 388 bp long segment of the control region (Wenink et al., 1993). Of the 388 nucleotide positions aligned, 104 (26.7%) were variable. A total of 98 different haplotypes could be recorded.
Parasite investigation
General morphometric data, in particular total length, standard length, fork length, head length, snout length (SL, to the nearest 0.1 cm), total weight, gutted weight, liver weight, gonad weight, intestine weight, full stomach weight, empty stomach weight (TW, to the nearest 0.1 g) as well as gender were recorded.
After fish morphometry and gut content analyses the presence of metazoan parasites within pylorus, gills, intestine and body cavity were studied. Studies on the parasite endofauna of Mullus surmuletus published so far mainly focus on helminths (Hristovski et al., 1995), among which digeneans are most diverse and abundant (Le Pommelet et al., 1997). Two digenean genera regarded more explicitly are Holorchis (Bartoli and Bray, 1996) and Opecoeloides (Jousson and Bartoli, 2000). Other publications on parasitism compare helminth infestation of mullets with that of other demersal teleosts (Hristovski and Jardas, 1983; Jardas and Hristovski, 1985; Hristovski and Jardas, 1991; Arculeo et al., 1997). With one cestode, four digeneans, at least five nematodes, one acanthocephalan, one copepod and at least one isopod species, a total of at least 13 different parasite species were detected.
The following parasite species were found in the specimens analysed:
1. Tetraphilidea indet. Scolex pleuronectis Cestoda
2. Opecoeloides furcatus Digenea
3. Derogenes varicus Digenea
4. Timonia mediterranea Digenea
5. Holorchis legendrei Digenea
6. Nematoda indet. (to be identified) Nematoda
7. Hysterothylacium aduncum Nematoda
8. Nematoda Ascarophis/ Capillaria Nematoda
9. Anisakis spp. Nematoda
10. Anisakis simplex Nematoda
11. Corynosoma wegeneri Acanthocaphala
12. Hatschekia mulli Copepoda
13. Gnathia spp. Isopoda
References
Arculeo, M., Hristosvki, N. and S. Riggio. 1997. Helminth infestation of three fishes (Serranus scriba, Mullus surmuletus, Scorpaena porcus) from a coastal seaground in the Gulf of Palermo (Thyrrhenian Sea). Italian Journal of Zoology 64 (3): 283-286.
Bartoli, A. and A.R. Bray. 1996. Description of three species of Holorchis Stossich, 1901 (Digenea: Lepocreadiidae) from marine fishes off Corsica. Systematic Parsitology 35 (2): 133-143.
Hristovski, N.D. and I. Jardas. 1983. A contribution to the knowledge of the helminth fauna of fishes from the coastal waters of the mid-Dalmatian insular area of the Adriatic Sea. Acta Adriatica 24: 179–191.
Hristovski, N. and I. Jardas. 1991. Endohelminths of fishes from the mid-Dalmatian region of the Adriatic Sea (A review). Acta Adriatica 32: 671–681.
Hristovski, N., Jardas, I. and I. Onofri. 1995. Helminthofauna of Red Mullet (Mullus barbatus L., Mullus surmuletus L., Pisces, Mullidae) in the waters of the Adriatic and of the Aegean Sea. Proceedings of the Institute of Fisheries, Varna, Volume XXIII: 169-177.
Jardas, I. and N. Hristovski. 1985. A new contribution to the knowledge of helminth parasite fauna of fishes from the channels between the mid-Dalmatian Islands, Adriatic Sea. Acta Adriatica 26: 145–164.
Jousson, O. and P. Bartoli. 2000. The life cycleof Opecoeloides columbellae (Pagenstecher, 1863) n. comb, (Digenea, Opecoelidae): Evidence from molecules and morphology. International Journal for Parasitology 30 (6): 747-760.
Le Pommelet, E., Bartoli, P. and P. Silan. 1997. Biodiversity of the digeneans and other intestinal helminths of goatfishes: A review for Mullus surmuletus (Linne, 1758) and M-barbatus (L., 1758) in the Mediterranean basin. Annales des Sciences-Naturelles et Biologie Animale 18 (4): 117-133.
Wenink, P.W., Baker, A.J. and M.G.J .Tilanus 1993. Hypervariable-Control-Region Sequences Reveal Global Population Structuring in a Long-Distance Migrant Shorebird, the Dunlin (Calidris alpina). PNAS 90: 94-98.