Sublethal effects of the herbicide diuron on the freshwater snail Physella acuta

Diuron is an herbicide present in European rivers at concentrations of environmental concern. Its effects on pulmonate gastropods are not well studied. A 16-day bioassay at five concentrations, including realistic ones, was performed with the freshwater snail Physa acuta to determine the effects of this herbicide on reproductive and metabolic traits as well as tissues and organs. The responses measured were survival, biomass, reproduction, motility, carbon (C) and nitrogen (N) contents and histology. Diuron at concentrations similar to those found in freshwater environments (9.5 µg/L) causes sublethal effects in the freshwater snail.  Results showed an increase in the C:N molar ratio at 9.5, 46.5 and 1172.5 mg/L and in the volume of secretory cells in the tegument at the same concentrations. The number of egg clutches increased slightly from a concentration of 46.5 mg/L, but this was not statistically significant. No effects on locomotor ability, biomass or survival, even at the highest concentration (1172.5 mg/L), were detected.