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) inTisbe battagliai(Crustacea, Copepoda, Harpacticoida) have been evaluated.T. battagliaiis 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 usingT. battagliaiholds much promise as an in vivo test for developmental and reproductive effects in aquatic Crustacea.