Development of copepod nauplii to copepodites - A parameter for chronic toxicity including endocrine disruption

Test compounds including natural hormones, endocrine disrupters, environmen tally occurring compounds, and reference compounds were tested for acute to xicity and inhibitory effect on larval development in the copepod Acartia t onsa. Three compounds, 17 alpha -ethinylestradiol, p-octylphenol, and tamox ifen, known for their differing effects on the vertebrate estrogen system, were potent inhibitors of naupliar development. Other estrogens, 17 beta -e stradiol, estrone, and bisphenol A, had little potency. Testosterone and pr ogesterone did not inhibit development, but the antiandrogen flutamide had inhibitory effect. Juvenile hormone III was a potent inhibitor, as was expe cted based on the literature, whereas 20-hydroxyecdysone had no effect. 3,4 -Dichloroaniline was inhibitory on development, whereas other control compo unds, potassium dichromate and 3,5-dichlorophenol, did not inhibit developm ent. Six of the 17 test compounds had 50% lethal concentration to 50% effec tive concentration (EC50) ratios higher than 10. The results suggest that n aupliar development, as a parameter, is able to detect hormonal disrupters in addition to other chemicals that have other specific modes of action.