Cadmium uptake and oxidative-stress-induced DNA alterations in the freshwater cladoceran Moina macrocopa (Straus 1820) following consecutive short-term exposure assessments

Moina macrocopa is a toxicologically less explored, yet widely distributed freshwater cladoceran found worldwide. The present study is aimed at determining the cadmium (Cd) uptake and Cd-induced molecular and biochemical biomarkers, including DNA damage and antioxidant enzyme (i.e., catalase (CAT) and glutathione S-transferase (GST)) responses, in M. macrocopa upon short-term (48 h) exposure assessments. The Cd uptake was determined using a Cd-sensitive fluorescence probe. The results indicated a concentration-dependent Cd internalization, statistically significant in neonates exposed to ≥ 5 Cd μg/L. DNA damage was detected by the randomly amplified polymorphic DNA (RAPD) technique. Significant DNA alterations were observed in individuals exposed to ≥ 10 Cd μg/L. Though there was an increasing trend of CAT activity induction with increasing Cd concentrations, it was not statistically significant among treatments with different Cd concentrations. In contrast, low Cd concentration (10 μg/L) significantly induced GST levels, and higher concentration (50 μg/L) significantly inhibited the GST levels. Moreover, a path analysis revealed that the internalization of Cd has a causal mechanism of induction of CAT activities which consequently cause DNA damage. Taken together, these results indicated that the internalization of Cd in M. macrocopa has the potential to cause oxidative stress even at sublethal concentrations, which may be one of the underlying causes of the observed DNA damage. Furthermore, our findings highlight the importance of utilizing molecular and biochemical biomarkers for toxicity assessment in cladocerans owing to their high sensitivity and rapid responses even under short-term exposure conditions with low concentrations.