Methods for Conducting Snail (Aplexa hypnorum) Embryo through Adult Exposures: Effects of Cadmium and Reduced pH Levels

摘要

Two separate embryo through adult exposures were conducted with cadmium and with reduced pH levels to validate various test methodologies and to determine the feasibility of testing and ease of handling the freshwater snail (Aplexa hypnorum) in a test system designed for fish bioassays. Exposure of snails, from embryos through adult reproductive maturity to cadmium chloride produced delayed hatch, reductions in percentage hatch and survival, and reduced growth when compared to a control. Based on these effects, the maximum acceptable toxicant concentration in Lake Superior water was between 4.41 and 7.63 micrograms cadmium/l in one test and between 2.50 and 4.79 micrograms cadmium/l in another test. Adult snails were exposed to determine a 96-hr LC50 of 93 micrograms cadmium/l. Exposure of embryonic, larval and adult snails to a pH range of 5.00-5.75 caused delayed hatching, reduced combined hatchability and survival, reduced 26-day growth, and a reduction in the number of egg masses per adult snail.