Bioaccumulation of selected metals in Lamproglena clariae Fryer, 1956 infecting Clarias gariepinus (Burchell, 1822) collected from six sampling sites along the Vaal River, South Africa

Lamproglena clariae, a gill parasite of Clarias gariepinus has previously been identified as a valuable indicator of effect for organic and metal pollution. The current study evaluates it as a bioindicator of metal accumulation by recording the concentration (mg/kg) of Mn, Fe, Zn, Se, and Sr in adult females and eggs collected at six sites along the Vaal River, South Africa. The data are compared to the metal concentrations recorded in water and sediment, and with infection variables calculated for L. clariae collected from C. gariepinus in March 2017 and October 2018. Metal concentrations in parasite samples were measured utilizing total reflection X-ray fluorescence spectroscopy. This was the first time this method was used to measure metal concentration in L. clariae. Manganese, Fe, Cu, Se, and Sr concentrations differed between adult females and egg specimens and between the six sampling sites, following the difference in the metal concentrations in the water and sediment samples. More polluted sites had low prevalence and low abundance of L. clariae. In adult females, Mn, Fe, Cu, Zn, Se, and Sr had higher concentrations than the water at the more polluted sites. Metal concentration (Mn, Zn, Cu, and Se) was higher in adult females compared to eggs. However, the Fe concentrations were higher in eggs than in adult females. Metal concentrations in L. clariae females were generally higher than levels recorded in water and sediment samples, indicating biomagnification, and supporting the viability of L. clariae as an accumulation indicator. High concentrations of Fe in eggs suggest that Fe elimination may occur via vitellin maternal transfer to larvae. Practitioner Points: Fish ectoparasites have not received sufficient evaluation as indicators of pollution. Lamproglena clariae bioaccumulates metals in polluted environments. Lamproglena clariae eggs accumulate Fe to higher concentrations than the females that produce them.