Testosterone and energy metabolism in the estuarine mysid Neomysis integer (Crustacea: Mysidacea) following exposure to endocrine disruptors

A diverse set of reference compounds suspected of having an endocrine-disrupting mode of action (i.e., testosterone, flutamide, ethinylestradiol, precocene, nonylphenol, fenoxycarb, and methoprene) were tested for acute toxicity to the estuarine mysid Neomysis integer (Crustacea: Mysidacea). Neomysis integer was very sensitive to all tested compounds, with 96-h median lethal concentrations in a narrow range between 0.32 and 1.95 mg/L. The pesticides methoprene and fenoxycarb, both synthetic insect juvenile hormone analogs, were most toxic to N. integer. In addition, the short-term sublethal effects of methoprene and nonylphenol (an estrogen agonist) on the energy and steroid metabolism of N. integer were evaluated. Both compounds significantly affected energy and testosterone metabolism of N. integer at concentrations below acute toxicity levels. Energy consumption in methoprene- and nonylphenol-exposed mysids was significantly induced at 100 μg/L, resulting in a lower cellular energy allocation in these animals. Testosterone phase I metabolism was affected at 10 μg/L, whereas glycosylation was the most important phase II pathway affected in mysids exposed to 100 μg/L of both compounds. Methoprene exposure resulted in a concentration-dependent increase in the metabolic androgenization ratio. Mysids exposed to nonylphenol at 10 μg/L had a significantly higher metabolic androgenization ratio. The present study indicates that energy and testosterone metabolism of mysids, as endpoints, are able to detect endocrine-disruptive activity of chemicals after short-term exposure to environmentally realistic levels of endocrine disruptors.