First record of trace element accumulation in a freshwater ectoparasite, Paradiplozoon ichthyoxanthon (Monogenea; Diplozoidae), infecting the gills of two yellowfish species, Labeobarbus aeneus and Labeobarbus kimberleyensis

Beric M Gilbert; Franz Jirsa; Annemariè Avenant-Oldewage

doi:10.1016/j.jtemb.2022.127053

First record of trace element accumulation in a freshwater ectoparasite, Paradiplozoon ichthyoxanthon (Monogenea; Diplozoidae), infecting the gills of two yellowfish species, Labeobarbus aeneus and Labeobarbus kimberleyensis

J Trace Elem Med Biol. 2022 Dec:74:127053. doi: 10.1016/j.jtemb.2022.127053. Epub 2022 Aug 3.

Authors

Beric M Gilbert¹, Franz Jirsa², Annemariè Avenant-Oldewage³

Affiliations

¹ University of Johannesburg, Department of Zoology, P.O. Box 524, Auckland Park 2006, South Africa. Electronic address: bericg@uj.ac.za.
² University of Johannesburg, Department of Zoology, P.O. Box 524, Auckland Park 2006, South Africa; University of Vienna, Faculty of Chemistry, Institute of Inorganic Chemistry, Althanstrasse 14, 1090 Vienna, Austria. Electronic address: franz.jirsa@univie.ac.at.
³ University of Johannesburg, Department of Zoology, P.O. Box 524, Auckland Park 2006, South Africa. Electronic address: aoldewage@uj.ac.za.

PMID: 35939924
DOI: 10.1016/j.jtemb.2022.127053

Abstract

Background: Elevated levels of trace elements in the aquatic environment poses risks to the health of biota and humans. Parasites are important components in ecosystems; responding to changes in the health of aquatic ecosystems and can accumulate trace elements in their tissues to higher levels than their hosts. Monogeneans are an important group of fish ectoparasites being directly exposed to the aquatic environment.

Methods: In this study concentrations of Ti, Fe, Cu, Zn, Rb, Sr and Ag were analysed in the monogenean parasite, Paradiplozoon ichthyoxanthon (by total reflection x-ray fluorescence spectrometry and graphite furnace atomic absorption spectrometry), and the muscle, liver and gills of two host fish species, Labeobarbus aeneus and Labeobarbus kimberleyensis (by inductively coupled plasma -- mass spectrometry).

Results: Most striking was the accumulation pattern for Zn in parasites; mean levels of Zn were as high as 1448 and 1652 mg kg^-1 dw, respectively, with no significant difference between the two host-parasite groups, leading to bioconcentration factors of approximately 93 (parasite/fish muscle) and 15 (parasite/fish liver). In addition, Fe was accumulated in the parasite to a higher degree compared to the fish hosts' tissues. Cu levels were higher in P. ichthyoxanthon than in the muscle tissue of both host fishes, but lower than liver tissue.

Conclusion: These findings demonstrate the usefulness of this parasite species as a sentinel organism in aquatic ecosystems it inhabits for Fe and Zn. Other trace elements under investigation were not accumulated higher in the parasite compared to its fish host. Lower Rb levels in the parasite compared to its hosts indicate no biomagnification of this metal. Further investigations are required to determine if similar trends in trace element accumulation occur in other monogeneans.

Data availability: All data generated in the analysis of host and parasite tissues are presented in the manuscript.

Keywords: Bioaccumulation; Parasites as sentinels; Rubidium; Vaal River; Water quality; Zinc.

MeSH terms

Animals
Cyprinidae* / parasitology
Ecosystem
Environmental Monitoring / methods
Fresh Water
Gills
Graphite*
Humans
Trace Elements* / analysis
Trematoda* / physiology
Water Pollutants, Chemical* / analysis

Substances

Trace Elements
Water Pollutants, Chemical
Graphite