Identification of mRNA expressions as biomarkers of environmental pollutants in the great pond snail (Lymnaea stagnalis)

Abstract: The great pond snail, Lymnaea stagnalis is considered a sensitive species to environmentalpollution and is used in ecotoxicology testing. The snail is naturally found in the environment inthe Holarctic realm in Europe, northern America and Asia but also in some parts of Australia. Itis a species of great interest for ecotoxicology studies and is used in research where commonendpoints are reproduction, mortality and immune responses. In this study we wanted to establisha method of using gene expressions in L. stagnalis as biomarkers of chemicals and pollutants inSTP effluent water. The study was conducted in two different experiments where gene expressionfor elongation factor 1a (ef1a), nuclear hormone receptor 3d (nr3d), cytochrome p450 3 (cyp3),metallothionein (mt), catalase (cat), glutathione peroxidase (gpx), and yolk ferritin (yf) from thehepatopancreas of L. stagnalis were measured. In experiment 1, animals were exposed tocadmium, 17α-ethinylestradiol, diclofenac, tramadol, PCB and a solvent control for seven days.In experiment 2 one group of animals were exposed to regular STP effluent water (UT), onegroup exposed to regular STP with an additional treatment of ozone (OZ), one group exposed toregular STP with an additional treatment of granulated active carbon (GAC) and finally, one lastgroup exposed to tap water (KV) as a control. The exposures lasted three weeks. In experiment 1,yf was upregulated 1.4-fold in snails exposed to PBC. In experiment 2, differences between thewaters were seen in the expressions of cyp3, gpx and yf. The expression of cyp3 was lower in theGAC group compared to the other groups. There was a difference in the expression of gpxbetween GAC and OZ but not compared to regular effluent water, UT or the tap water, KV. Theexpression of yf was higher in KV, but not different between the other groups. In summary, the yfgene expression in L. stagnalis is altered by PCB. There were also measurable effects of theexpression of cyp3 and gpx in snails exposed to effluent water treated with GAC. Conclusions ofthe results are difficult to draw but the changes in gene expressions indicates that L. stagnalis is apromising candidate as a model organism to gene expressions as biomarkers. Further studies arehowever needed to refine the method.