Intestinal Nematodes Affect Selenium Bioaccumulation, Oxidative Stress Biomarkers, and Health Parameters in Juvenile Rainbow Trout (Oncorhynchus mykiss)

Abstract

In environmental studies, parasites are often seen as a product of enhanced host susceptibility due to exposure to one or several stressors, whereas potential consequences of infections on host responses are often overlooked. Therefore, the present study focused on effects of parasitism on bioaccumulation of selenium (Se) in rainbow trout (Oncorhynchus mykiss). Joint effects of biological (parasite) and chemical (Se) stressors on biomarkers of oxidative stress (glutathione-S-transferase (GST), superoxide dismutase (SOD)), and fish health (condition factor (K), hepatosomatic index (HSI), gross energy) were also examined. Fish of the control group received uncontaminated food, while test fish, either experimentally infected with the nematode Raphidascaris acus or not, were exposed to dietary selenomethionine (Se-Met) at an environmentally relevant dose over 7 weeks. Selenium bioaccumulation by the parasite was low relative to its host, and parasitized trout showed slowed Se accumulation in the muscle as compared to uninfected fish. Furthermore, GST and SOD activities of trout exposed to both Se-Met and parasites were generally significantly lower than in fish exposed to Se-Met alone. Gross energy concentrations, but not K or HSI, were reduced in fish exposed to both Se-Met and R. acus. Together the experiment strongly calls for consideration of parasites when interpreting effects of pollutants on aquatic organisms in field investigations.

Host-parasite relationships as determinants of heavy metal concentrations in perch (Perca fluviatilis) and its intestinal parasite infection

“…Some other studies (Sures et al 1999a;Sures 2002) pointed out that the competition for minerals may lead to extra absorption of non-essential elements such as toxic lead and cadmium due to their similarity in chemical properties. This extra absorption of toxic metals from host tissues has occasionally been interpreted as a "beneficial aspect" of parasitism (Sures and Siddall, 1999;Turčeková et al, 2002;Eira et al, 2009;Hursky and Pietrock, 2015). However, no ecoparasitological studies dealing with relationships between heavymetal concentrations in different parasite species within the helminth infrapopulation in the host' intestine was done.…”

Development and Validation of a Biodynamic Model for Mechanistically Predicting Metal Accumulation in Fish-Parasite Systems

“…This might account for the less unequal partitioning of Fe, Cu, and Zn in the chub-acanthocephalan system. The lower concentration of Se in the nematode Raphidascaris acus compared to the concentration in the trout Oncorhynchus mykiss as found by Hursky and Pietrock [85] might be related to the limited induction of bile acids due to the low concentration of Se in the investigated trout. In particular, the concentration of Se in the trout investigated in the study of Hursky and Pietrock [85] was lower than the concentration of Se in the muscle of the bream in the study of Mazhar et al [87] by more than one order of magnitude.…”

“…In particular, Genc et al [96] demonstrated that the accumulation of Cd, Cr, Cu, Fe, Hg, Mn, Pb and Zn in the European eel Anguilla anguilla infected with the nematode Anguillicola crassus was not significantly different from that in the uninfected eel. By contrast, infection with parasites has been reported to reduce the concentration of metals accumulated in the fish host in many of previous studies [18,20,85,97]. Sures and Siddall [18] and Sures et al [20] reported lower concentrations of Pb in the chub infected with the acanthocephalan P .…”

“…This was also seen when the concentration of metals in parasites was compared with the concentration in fish tissues (Table 3). However, Hursky and Pietrock [85] found an opposite observation when the trout was exposed to Se via dietary pathway.…”

“…laevis than in the uninfected chub. In the study of Hursky and Pietrock [85], the infection with the nematode R . acus reduced metal concentrations in the trout O .…”