Evaluation of the Efficacy of Extrapolation Population Modeling to Predict the Dynamics of Americamysis Bahia Populations in the Laboratory

Abstract

An age-classified projection matrix model has been developed to extrapolate the chronic (28-35 d) demographic responses of Americamysis bahia (formerly Mysidopsis bahia) to population-level response. This study was conducted to evaluate the efficacy of this model for predicting the population behavior of A. bahia held (for more than three generations) under controlled laboratory exposure conditions. The research involved the performance of a standard life-cycle test and a multigenerational (greater than three mysid generations, 55 d) assay using A. bahia to experimentally evaluate model predictions regarding population-level risks of chemical exposure. The organic compound para-nonylphenol was chosen as the chemical stressor in assays. This compound is a ubiquitous contaminant and suspected endocrine disruptor. Utilizing data obtained during the standard life-cycle test, aggregate estimates of population growth rate (lambda) and measured p-nonylphenol concentration were used to develop an exposure-response model of population-level effects. These estimates provided the basis of predictions for the long-term dynamics of mysid populations exposed to p-nonylphenol. The veracity of the mysid population model was evaluated through quantitative comparisons of model predictions based on the life-cycle test with dynamics of the experimental populations (multigenerational assay results). The results indicate that the population model was able to project within a few micrograms per liter the concentration where population-level effects would begin to occur (projected 16 micrograms/L from the model vs measured 19 micrograms/L from the multigenerational assay).

Mysid crustaceans as standard models for the screening and testing of endocrine-disrupting chemicals

“…These results have also been observed in later mysid population studies by Raimondo and McKenney (2006). Kuhn et al (2001) confirmed that mysid models generated from laboratoryderived survival and reproduction could predict population projections of mysids in laboratory conditions. The mysid models described here are useful tools for linking the organism-level responses to population viability, yet future research that may provide information to incorporate density dependence and environmental stochasticity into mysid models will improve probabilistic risk assessment of mysid populations.…”

“…In this analysis, reduced reproduction was the primary contributor to reduced population growth rate for most concentrations, emphasizing the importance of altered reproduction in mysid population-level risk assessment (Raimondo and McKenney, 2006). Previous population modeling efforts by Kuhn et al (2000Kuhn et al ( , 2001 were aimed at evaluating the ecological relevance of mysid bioassays and population models. Kuhn et al (2000) found high correlations of 96h-LC50 values and toxicant concentrations where populations would begin to decline.…”

“…Mysid models have been developed to link impairments of vital rates, such as survival and reproduction, to long-term mysid population viability (Kuhn et al, 2000(Kuhn et al, , 2001Raimondo and McKenney, 2005a. McKenney (2005a, 2005b) developed matrix population models from survival and reproduction measured in life table response experiments for population-level risk assessments of methoprene and thiobencarb exposure on A. bahia.…”

“…Marine (10-20‰), >20°C yes Domingues et al, 1999;Reitsema and Neff, 1980 Holmesimysis costata (= Acanthomysis sculpta) Gorokhova, 2002;De Lisle and Roberts, 1994;Cuzin-Roudy and Saleuddin, 1989;Fockedey et al, 2006;Ghekiere et al, 2006a Energy metabolism; O:N ratio, C:N ratio Respiration, Biochemical composition, Crustacean hyperglycemic hormone McKenney 1998McKenney , 1999Roast et al, 1999b;Verslycke et al, 2003cVerslycke et al, , 2004dOECD, 2006;Chang, 2005 Embryonic development Greenwood et al, 1989;Wortham and Price, 2002;Fockedey et al, 2006;Ghekiere et al, 2006a Sexual maturatity, Time to first brood release, Egg development time ASTM, 1999;OECD, 2006 Sex ratio and intersexuality ASTM, 1999;OECD, 2006 Fecundity (brood size) ASTM, 1999;USEPA, 1995aUSEPA, , 1995bOECD, 2006Vitellogenesis Tuberty et al, 2002Ghekiere et al, 2004Ghekiere et al, , 2005Ghekiere et al, , 2006c Population dynamics Kuhn et al, 2000Kuhn et al, , 2001Raimondo and McKenney, 2005a Ecdysteroid metabolism, Ecdysteroid receptor interaction Cuzin-Roudy and Saleuddin, 1989;Yokota et al, 2005;Verslycke et al (unpublished data) Steroid metabolism Verslycke et al, 2002Verslycke et al, , 2003aVersl...…”

Mysid population responses to resource limitation differ from those predicted by cohort studies

“…Similarly, Gentile et al (1982) used Euler-Lotka formulations to estimate population growth rate from A. bahia cohort data. Although demographic model projections were tested by Kuhn et al (2001) using observations of total population size, estimation of specific vital rates within these intact populations was not possible. Markert et al (2010) used scalar density-dependent models to separate genetic diversity and resource effects on A. bahia population size.…”