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

<jats:title>Abstract</jats:title><jats:p>Life‐cycle effects of a reference ecdysteroid, 20‐hydroxyecdysone (20‐HEC) and the model xenoestrogen, diethylstil‐bestrol (DES) in<jats:italic>Tisbe battagliai</jats:italic>(Crustacea, Copepoda, Harpacticoida) have been evaluated.<jats:italic>T. battagliai</jats:italic>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 (&lt;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 (<jats:italic>p</jats:italic>&lt; 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<jats:italic>T. battagliai</jats:italic>holds much promise as an in vivo test for developmental and reproductive effects in aquatic Crustacea.</jats:p>