PARENT SESSION
PT2 - Endocrine Disruption
Tuesday, 19 November 2002
8:00 AM to 6:30 PM
Exhibit Hall

(P564) Effects of 17-estradiol,atrazine,and nonylphenol on the sex ratios of the Atlantic silverside, Menidia menida.

Champlin, Denise^*,1, Nacci, Diane¹, Serbst, Jonathan¹, Jayaraman, Saro¹, Pelletier, Marguerite¹, Chandlee, Mary², Specker, Jennifer², ¹ US Environmental Protection Agency, Atlantic Ecology Division, Narragansett, RI, US² University of Rhode Island, Graduate School of Oceanography, Narragansett, RI, US

ABSTRACT- The gender of the common estuarine fish, Atlantic silverside (Menidia menidia), is determined by temperature during early larval development. Under laboratory conditions, the ratio of males to females was determined to be 80:20 at 25°C and 20:80 at 15°C. This study used this model system to evaluate the effects of three estrogenic chemicals on the gender of this atherinid fish reared at male-producing temperature. Newly hatched Menidia were exposed to a range of concentrations of 17-estradiol (E2), atrazine, and nonylphenol for 35 days. The fish were then transferred into clean seawater, grown to total lengths of 35mm-67mm, and necropsied to determine gender or preserved for future histological analysis. While histological analyses may provide additional information about sexual development in exposed fish, gender analysis indicated that larval exposure to estrogenic compounds can alter sex ratios. Specifically, gender analysis indicated that the ratio of males to females declined in a concentration-responsive manner to 0:100 at .05 g/l, following exposures to average measured concentrations of E2 ranging from 0.008 g/l to 0.17 g/l. Average measured concentrations of atrazine ranging from 20 g/l to 240 g/l produced small and variable reductions in the proportion of males, reaching a low of 50:50 at 57 g/l. Average measured concentrations of nonylphenol ranging from 1.5 g/l to 53 g/l also produced variable reductions in the proportion of males, reaching a low of at 53 g/l. These findings suggest that this model system may be useful to investigate the effects of chemicals that affect sexual development and have the potential to alter sex ratios and reproductive capacity of wild fish populations.

Key words: endocrine disruptor, estradiol, atrazine, nonylphenol