engleski

CAN FISH INTESTINAL PARASITES ACANTHOCEPHALANS PROTECT THE FISH AGAINST METAL ACCUMULATION?

Acanthocephalans are widespread and common fish parasites which live inside the intestine and absorb nutrients since they lack an own mouth and intestinal system. Parasites can cause mechanical (fusion of gill lamellae, tissue replacement), physiological (cell proliferation, immunomodulation, altered growth) and reproductive damage in fishes. Consequently, fishes under the stress of their parasite load are weakened and become more susceptible to other environmental stressors including contaminants. Metal contamination in aquatic systems is a critical environmental issue due to metal uptake, accumulation and possible toxicity in aquatic organisms. In the past decades it was shown that acanthocephalans can accumulate metals at concentrations that are orders of magnitude higher than those in the commonly used indicator organisms like fishes, bivalves or crustaceans. Accordingly, attempts were made to utilize acanthocephalans as biological indicators of metal exposure in environmental risk assessment studies. The aim of this study was to compare concentrations of essential (Cu, Fe) and non-essential metals (Cd, Pb) in acanthocephalan (Pomphorhynchus laevis Müller) and its definitive host European chub (Squalius cephalus L.) from the Sava River. Moreover, possible protective role of parasites against metal accumulation in fish was studied by comparison of metal levels in chub infected with P. laevis and uninfected chub. Metal levels in P. laevis were higher than in chub intestine following the order: Pb>Cd>Cu. Chub infected with P. laevis had lower Cu, Cd and Pb levels than uninfected chub, indicating possible protective role of parasites against metal accumulation in fish, even in a river flow with low metal contamination. In addition, metal distribution among cytosolic protein fractions in acanthocephalan and fish indicated comparable metal association, for Cu and Cd with metal binding protein, metallothionein, for Fe with Fe-storage protein, ferritin and for Pb with proteins of medium molecular masses. The fractionation of cell cytosols was carried out by size exclusion high performance liquid chromatography (SE-HPLC ; Superdex™ 200 10/300 GL column) and metal measurements by high resolution inductively coupled plasma mass spectrometry (HR ICP-MS). The obtained information within this study presented the starting point for identification and characterization of specific metal-binding proteins in chub and acanthocephalans, and moreover, indicated the protective role of acanthocephalans against metal accumulation in fish.

acanthocephalan Pomphorhynchus laevis ; fish Squalius cephalus L. ; essential/non-essential metals

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