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, diethylstilbestrol (DES) in Tisbe batragliai (C rustacea, Copepoda, Harpacticoida) have been evaluated. T, battagliai is a sexually reproducing species that is representative of an ecologically dive rse group of aquatic Crustacea and is highly amenable to laboratory life-cy cle 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 degrees C. A mortality of approximate to 40% occurred after 9-d exposure to 20-HEC at 269 mu g/L, whereas significant (1 7.5%) mortality (p < 0.05) occurred after 4-d exposure to DES at 100 mu g/L . Adult males and females were paired after day 10, and exposures continued to investigate effects on reproductive output (21-d total exposure). In su mmary, the 21-d LC50 values (with 95% confidence intervals) for 20-HEC and DES were 53.4 mu g/L (36.5-78.7) and 31.6 mu g/L (10-100), respectively. Fo r 20-HEC, the 21-d no observed effect concentration (NOEC) for survival was 26.9 mu g/L, whereas reproduction was a more sensitive endpoint (NOEC = 8. 7 mu g/L). For DES, survival and reproduction were equally sensitive, and b oth gave an NOEC value of 10 mu g/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 e ffects in aquatic Crustacea.