Mercury content in the parasite-host system of Ligula intestinalis and Abramis brama and the effect of the parasite on fish muscle composition

Abstract

The bioaccumulation potential of parasites resulting from the competition for chemical elements including heavy metals represents a valuable instrument of evaluating the functions of the parasite-host system. In the present study, the effect of the parasite-host system of Ligula intestinalis and Abramis brama on the mercury concentrations and fish muscle composition of infected and non-infected fish was evaluated. Nine parasitized and seven non-parasitized fish were studied. The total mercury content in the samples was determined by the atomic-absorption spectrophotometry method. Standard indicators of the chemical composition of muscles (dry matter, crude protein, fats, and ash) and a spectrum of fatty acids were evaluated. The mean mercury concentration in the biomass of plerocercoids was 0.045 ± 0.025 mg·kg-1; about × 7 lower compared to fish muscles. The mean mercury concentration in the muscles of infected and non-infected fish was 0.36 ± 0.11 and 0.24 ± 0.1, respectively. There was no difference in the composition of fish muscles and the spectrum of fatty acids. Ligula intestinalis takes nutrients from the fish body but according to the results of our study, the withdrawal of the monitored nutrients was uniform without any selection. Mercury is not efficiently accumulated by plerocercoids of Ligula intestinalis. This study brings novel data for this heavy metal and for this parasite host system.