Abstract
Due to the global scarcity of freshwater, toxicants are becoming increasingly concentrated
affecting aquatic ecosystems. Vanadium (V) is one such toxicant that has the ability to affect
organisms. Vanadium pentoxide (V2O5) can act as an oxidizing agent and can therefore cause
oxidative damage. A 96-hour broad-range finding exposure was conducted, thereafter the LC50
determined. A definitive acute (96-hr) and sub-chronic (12-day) (LC50) test was done using V2O5
on 14-day old Oreochromis mossambicus fry. The acute (96-hr) LC50 was calculated to be 12.932
mg/L and the sub-chronic (12-day) LC50 was calculated to be 6.554 mg/L using probit analysis.
Once the LC50 for V2O5 was obtained, the concentration was used to determine the acute (96-hr)
exposure concentrations for the adult Oreochromis mossambicus, which were 1.29 mg/L, 1.93
mg/L, and 2.58 mg/L. Vanadium accumulation and biomarker analysis were conducted once the
relevant tissues had been excised from the fish. Univariate and multivariate analysis were used
to determine significant differences between exposure concentrations in both the gill and muscle
tissue for bioaccumulation and biomarker data. Vanadium accumulated in greater concentrations
in gill tissue compared to muscle tissue, due to gills being in constant contact with the environment
and primary uptake route of the metal. Accumulated V concentrations in the gill tissue increased
as the exposure concentration increased. Significant differences were found in metallothionein
(MT) content, superoxide dismutase (SOD) activity, catalase (CAT) activity, and protein carbonyl
(PC) induction. Metallothionein concentrations showed significant differences between control
and 1.93 mg/L and 2.58 mg/L V2O5 exposure concentrations. Superoxide dismutase activity
showed a significant increase from control to the 1.29 mg/L and 1.93 mg/L V2O5 exposure
concentrations and then decreased from 1.93 mg/L to 2.58 mg/L exposure concentrations, which
indicates ROS detoxification. Catalase activity showed a significant decrease from 1.29 mg/L
V2O5 exposure concentration to the two highest V2O5 exposure concentrations; this may be
attributed to potential SOD activity compensation. Protein carbonyl content significantly
decreased as the exposure concentrations of V2O5 increased, showing a decrease of protein
oxidation. These results show that V2O5 accumulates in specific organs in Oreochromis
mossambicus. The biomarker responses determined indicate that tilapia are able to cope with
increasing V2O5 concentrations through induction of MT proteins, SOD activity and CAT activity.