Development of a Sperm Cell Toxicity Test for Marine Waters

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Abstract
Preliminary methods for conducting a quick and sensitive sperm cell toxicity test for marine waters have been developed. This paper presents a simple static test in which sea urchin or sand dollar sperm cells are exposed to test or control solutions for short periods of time (typically 15 to 60 min). Eggs are added to the test containers after the sperm exposure period has ended, and a standard time is allowed for fertilization to take place before the eggs are fixed with formalin. Samples are then tabulated for fertilization success by noting the presence or absence of the fertilization membrane. The results are analyzed by standard statistical methods to yield a time-dependent median effective concentration (EC50) (that is, the concentration of the test material that is effective in reducing fertilization success by 50 percent) after a specified period of exposure.Sperm cell toxicity tests with two reference toxicants (silver nitrate and the pesticide endosulfan) showed that toxic responses were directly related to sperm exposure time. The 60-min EC50s and 95 percent fiducial limits for green sea urchin (Strongylocentrotus droebachiensis) sperm were 76 (57 to 103) and 168 (99 to 285) µg/litre for silver and endosulfan, respectively. The 60-min EC50s for sand dollar (Dendraster excentricus) sperm were 45 (34 to 61) and 147 (123 to 175) µg/litre for silver and endosulfan, respectively. Matrix bioassays using temperature, salinity, and toxicant concentration as variables showed that the toxic response to both silver and endosulfan generally increased with increasing temperature and decreasing salinity. One test series of silver and endosulfan in combination showed that toxicity was additive. Comparative sea urchin and sand dollar embryo tests (72 to 96 h) showed embryo sensitivity to be similar to sperm sensitivities with levels of effect (retardation of development) of 50 and 25 µg/litre, respectively, for silver and 253 and 158 µg/litre for endosulfan.Additional development and refinement of this sperm cell toxicity test should yield a rapid and sensitive procedure for screening large numbers of toxicants in marine waters, aid in the prediction of ecological effects, and provide an additional tool for the biomonitoring of receiving water quality.

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