Abstract
BackgroundMetal uptake and accumulation in fish parasites largely depends on the parasite group with acanthocephalans showing the highest accumulation rates. Additionally, developmental stage (larvae or adult) as well as parasite location in the host are suggested to be decisive factors for metal bioconcentration in parasites. By using barbel (Barbus barbus) simultaneously infected with nematode larvae in the body cavity and adult acanthocephalans in the intestine, the relative importance of all of these factors was compared in the same host.MethodsEleven elements Arsenic (As), Cadmium (Cd), Cobalt (Co), Copper (Cu), Iron (Fe), Manganese (Mn), Lead (Pb), Selenium (Se), Tin (Sn), Vanadium (V) and Zinc (Zn) were analyzed in barbel tissues (muscle, intestine, liver) as well as in their acanthocephalan parasites Pomphorhynchus laevis and the larval nematode Eustrongylides sp. (L4) using inductively coupled plasma mass spectrometry (ICP-MS).ResultsNine elements were detected in significantly higher levels in the parasites compared to host tissues. The element composition among parasites was found to be strongly dependent on parasite taxa/developmental stage and localization within the host. Intestinal acanthocephalans accumulated mainly toxic elements (As, Cd, Pb), whereas the intraperitoneal nematodes bioconcentrated essential elements (Co, Cu, Fe, Se, Zn).ConclusionOur results suggest that in addition to acanthocephalans, nematodes such as Eustrongylides sp. can also be applied as bioindicators for metal pollution. Using both parasite taxa simultaneously levels of a wide variety of elements (essential and non essential) can easily be obtained. Therefore this host-parasite system can be suggested as an appropriate tool for future metal monitoring studies, if double infected fish hosts are available.
Highlights
Metal uptake and accumulation in fish parasites largely depends on the parasite group with acanthocephalans showing the highest accumulation rates
Fish samples Fish infected simultaneously with P. laevis and larval nematodes of the genus Eustrongylides sp. were identified during a four years sampling of barbel from the Bulgarian part of the river Danube
Larval Eustrongylides sp. accumulated mainly essential elements, whereas the adult P. laevis showed a higher affinity to take up non-essential elements
Summary
Metal uptake and accumulation in fish parasites largely depends on the parasite group with acanthocephalans showing the highest accumulation rates. Metal accumulation in parasitic nematodes appears to be more variable than in acanthocephalans with usually only slightly higher concentrations of a few elements in adult Philometra cyprinirutili, P. ovata, Anisakis simplex and Anguillicola crassus in comparison to their fish host tissues [8,9,10,11,12]. Metals are transported by the circulatory system into the fish liver where they are bound in bile complexes and excreted into the intestine. They become available for the parasites located in the intestine. Intestinal parasites should have a better access to metals than parasites dwelling in the body cavity This assumption was tested in laboratory exposure experiments with the acanthocephalan P. laevis [13]. Individuals which penetrated the intestinal wall and which were found in the cavity of fish accumulated significantly less lead than the acanthocephalans in the intestinal lumen
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