title: Chronic toxicity of tributyltin to development and reproduction of the European freshwater snail Lymnaea stagnalis (L.).
abstract: Chronic toxicity, growth and reproduction were measured in the freshwater gastropod Lymnaea stagnalis exposed to waterborne bis(tri-n-butyltin) oxide (TBTO) over a range of four nominal concentrations (0-10microg TBTl(-1)). Egg development was completely inhibited at 10microg TBTl(-1), whilst abnormal embryonic development was observed at 1microg TBTl(-1). For the solvent control and the 0.01microg TBTl(-1)treatment group, normal development of L. stagnalis was observed. Survivorship of hatchlings was significantly reduced by TBT at 1microgl(-1) while inhibition of shell growth of L. stagnalis was also observed at this concentration. The data were used to determine intrinsic growth rates (r) using two theoretical approaches (the Euler-Lotka equation and a Leslie Matrix). Both approaches showed that survival, fecundity and population growth rate were reduced at 1microg TBTl(-1). Interestingly, at 0.01microg TBTl(-1) snails showed a higher fecundity and growth rate than in the solvent control. The TBT concentration at which the r would equal zero (ECr(0)) and the population NOEC (No Observed Effect Concentration) were estimated. The population NOEC was defined as either the lower 95% confidence or lower 95% pointwise percentile limit of the ECr(0). Values obtained using the two different approaches were similar and thus a geometric mean was calculated to obtain a final representative population NOEC value for L. stagnalis of 2745ng TBTl(-1). The present data together with chronic toxicity TBT data for freshwater organisms, obtained from peer-reviewed literature, were used to construct a species sensitivity distribution (SSD). A predicted no effect concentration was then derived from the SSD (hazardous concentration at 5%, i.e., HC5 or 95% protection level). This SSD was compared with the SSD derived from saltwater species datasets. The HC5 value for saltwater species (3.55ng TBTl(-1); lower confidence limit: 1.93ng TBTl(-1)) was significantly lower than that for freshwater species (30.13ng TBTl(-1); lower confidence limit: 9.23ng TBTl(-1)), indicating that saltwater species are probably more susceptible to TBT than their freshwater counterparts.
authors.affiliation: The Swire Institute of Marine Science, Department of Ecology and Biodiversity, The University of Hong Kong, Pokfulam, Hong Kong. kmyleung@hkucc.hku.hk
authors.forename: Kenneth M Y
authors.initials: KM
authors.lastname: Leung
authors.forename: Eric P M
authors.initials: EP
authors.lastname: Grist
authors.forename: Neil J
authors.initials: NJ
authors.lastname: Morley
authors.forename: David
authors.initials: D
authors.lastname: Morritt
authors.forename: Mark
authors.initials: M
authors.lastname: Crane
mesh_terms: D000818:Animals; D005060:Europe; D005618:Fresh Water / Q000737:chemistry*; D008195:Lymnaea / Q000187:drug effects / Q000254:growth & development; D012098:Reproduction / Q000187:drug effects; D013997:Time Factors; D036401:Toxicity Tests, Chronic; D014220:Trialkyltin Compounds / Q000633:toxicity*; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D014220:Trialkyltin Compounds; D014874:Water Pollutants, Chemical; C011559:tributyltin