Abstract
The copepod Lernaeosera lusci is a common ectoparasite of the hake Merluccius merluccius, which constitutes its definitive host. The present study is the first to investigate the impact of L. lusci and its infection intensity on the fatty acid (FA) composition and oil quality of its host. The results revealed a substantial decrease in the total FA content, which dropped by 50, 70 and 83% when fish was infected by one (L1), two (L2) and three (L3) parasites, respectively. The lipid profile showed a tendency for a significant decrease in the saturated fatty acid (SFA), monounsaturated fatty acid (MUFA) and polyunsaturated fatty acid (PUFA) levels in all parasitized groups and in a parasite load dependant manner (p < 0.05). The same tendency was observed for the most commonly analysed FA and in particular for essential FA, such as e arachidonic (ARA), eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids, which showed smaller amounts associated with L. lusci co-infection. From a nutritional standpoint, our findings revealed that L. lusci is able to cause severe deterioration in the nutritional quality of its host oil. In addition to the increase in the thrombogenicity index (IT) and the high atherogenicity index (IA) values, the low hypocholesterolemic / hypercholesterolemic fatty acid ratio (H/H) and the modest amount of DHA+EPA (20 and 10 mg/100g) recorded at heavy infection levels make the parasitized fish inadequate sources of these PUFA and unsuitable for consumers with special dietary needs.
Highlights
Fish samplesA total of 146 samples of European hake M. merluccius with similar size (18 ± 1.5 cm) were bought from fisherman at the port of Bizerte (Tunisian northern waters)
Our findings are in agreement with those of Huynh and Kitts (2009) who reported that unlike other lean fish, the pacific hake exhibited a typical pattern with the highest amount of saturated fatty acid (SFA) than monounsaturated fatty acid (MUFA)
It was found that Palmitic acid (C16:0) was the predominant fatty acid among the SFA fraction; whereas the most abundant MUFA was oleic acid (C18:1), followed by palmitoleic acid (C16:1) with 0.453 and 0.217 mg·g−1 respectively
Summary
A total of 146 samples of European hake M. merluccius with similar size (18 ± 1.5 cm) were bought from fisherman at the port of Bizerte (Tunisian northern waters). A total of 146 samples of European hake M. merluccius with similar size (18 ± 1.5 cm) were bought from fisherman at the port of Bizerte (Tunisian northern waters). The fish were immediately transported to the laboratory in polystyrene, ice-cooled boxes. Immature specimens were included in this study in order to avoid any inference with the reproduction cycle. All specimens were immediately examined to look for the presence of L. lusci. Specimens infected with L. lusci were further dissected and only samples without other macro parasites (such as worms) were kept to avoid any bias. The fish were determined to be free from infection with L. lusci or other macro parasites were taken as control samples. The fillet samples from the parasitized and unparasitized fish were weighed (5.0 ± 0.5 g), and stored at −30 °C until analysis
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