Salt-induced modulation of titanium nanoparticle accumulation with osmoregulatory and histological responses in freshwater mussels (Unio delicatus).
Armagan Meryem M, Celenk Alper A, Canli Esin G EG, Canli Mustafa M
The salinity of freshwaters can increase due to anthropogenic activities, which affects animal biology. This may be important for freshwater mussels, which are frequently used to monitor environmental pollution. Thus, the present study was undertaken to investigate the effects of TiO2 NPs and/or salt (NaCl) on titanium accumulation, ion-ATPase activity and histology in freshwater mussels (Unio delicatus). Data showed that mussels were extremely sensitive to salinity increases, as 70% of them died within 96 h in 6 ppt NaCl. There was a linear accumulation of TiO2 NPs in the gill and muscle regardless of salt level. However, accumulation in the gill was significantly higher (p < 0.05) at a higher salt level (1.50 ppt) than at a lower salt level (<0.25 ppt). Activities of Na-ATPase and Mg-ATPase in the gill and Ca-ATPase in the muscle of higher salt controls were significantly (p < 0.05) lower compared to those of lower salt controls. Exposure to TiO2 NPs alone significantly decreased Na-ATPase activity in the gill. Generally, there was no significant (p > 0.05) alteration in ATPase activity when mussels were exposed to TiO2 NPs at higher salt levels. Regression analyses showed a negative relationship between Ti levels and Na-ATPase activity in the gills of mussels exposed to TiO2 NPs alone. Likewise, outstanding histological differences occurred in the gills of mussels exposed to TiO2 NPs and/or higher salt levels. Nevertheless, 1.5 ppt NaCl alone did not cause any apparent tissue deformation. Data emphasised that salinity should be taken into account in environmental monitoring studies conducted on freshwater mussels.