A Parameter for Detecting Estrogenic Exposure in the Copepod Acartia tonsa

Literature on the basic endocrinology of crustaceans, such as crab, lobster and shrimp, suggest that estrogens, e.g., 17β-estradiol, are stimulating hormones in female sexual maturation and egg production in crustaceans. The copepod Acartia tonsa, has continuous egg production. A profile of the egg production per time unit through the maturation of this species may be used as an expression of the degree of maturation of the female internal reproductive organs. Comparison of control profiles with profiles of estrogen-exposed copepods may thus demonstrate that estrogen exposure results in a steeper maturation profile. The proposed endpoint was identified by exposing copepods to the natural estrogen 17β-estradiol and the antropogenic estrogen bisphenol A. Both compounds produced significant effects at 23 and 20 μg/L, respectively. Since bisphenol A is traditionally believed to be less estrogenic than 17β-estradiol, the nonestrogen 2,3-dichlorophenole was tested at 13.6 μg/L (molar concentration equal to 23 μg/L 17β-estradiol) to test if the response is a general nonestrogenic toxic stress effect. The 2,3-dichlorophenole produced no effect.