Life-cycle studies with marine copepods (Tisbe battagliai) exposed to 20-hydroxyecdysone and diethylstilbestrol

Life-cycle effects of a reference ecdysteroid, 20-hydroxyecdysone (20-HEC) and the model xenoestrogen, diethylstil-bestrol (DES) in Tisbe battagliai (Crustacea, Copepoda, Harpacticoida) have been evaluated. T. battagliai is a sexually reproducing species that is representative of an ecologically diverse group of aquatic Crustacea and is highly amenable to laboratory life-cycle studies. Newly released (<24-h old) Copepod nauplii were exposed to 20-HEC or DES and effects monitored in terms of survival, development, and sex ratio after 10 d at 20 ± 1°C. A mortality of ≈40% occurred after 9-d exposure to 20-HEC at 269 μg/L, whereas significant (17.5%) mortality (p < 0.05) occurred after 4-d exposure to DES at 100 μg/L. Adult males and females were paired after day 10, and exposures continued to investigate effects on reproductive output (21-d total exposure). In summary, the 21-d LC50 values (with 95% confidence intervals) for 20-HEC and DES were 53.4 μg/L (36.5–78.7) and 31.6 μg/L (10–100), respectively. For 20-HEC, the 21-d no observed effect concentration (NOEC) for survival was 26.9 μg/L, whereas reproduction was a more sensitive endpoint (NOEC = 8.7 μg/L). For DES, survival and reproduction were equally sensitive, and both gave an NOEC value of 10 μg/L (all based on nominal concentrations). These results suggest that the 21-d life-cycle protocol using T. battagliai holds much promise as an in vivo test for developmental and reproductive effects in aquatic Crustacea.