Changes in the physiological performance and energy metabolism of an estuarine mysid (Mysidopsis bahia) exposed in the laboratory through a complete life cycle to the defoliant DEF

Abstract

Measures of physiological performance and energy metabolism were made on an estuarine mysid ( Mysidopsis bahia) exposed throughout a life cycle to the defoliant DEF. Continuous exposure to DEF concentrations ≥ 0.246 μg/l reduced survival through release of the first brood. Young production by individual females was completely arrested in DEF concentrations ≥ 0.606 μg/l. Life-cycle exposure to concentrations ≥ 0.085 μg DEF/l reduced young production by the population. An interaction between mysid age and DEF exposure concentration modified growth rates and energy metabolism. Growth of early juveniles was not altered by DEF exposure. However, concentrations ≥ 0.140 μg/l and ≥ 0,085 μg/l retarded growth rates in older juveniles and young adults, respectively. Exposure to these same DEF concentrations stimulated respiration rates of most juvenile stages and young adults. Following 5-days exposure to DEF concentrations ≥ 0.085 μg/l, mysids excreted less ammonia. O:N ratios of unexposed mysids became lower as juveniles matured, while DEF exposure resulted in higher O:N ratios. Higher O:N ratios during maturation of DEF-exposed mysids suggests greater reliance on energy-rich lipid substrates to support elevated metabolic demands, leaving reduced lipid for reproductive preparations.