Simultaneous modelling of multiple endpoints in life-cycle toxicity tests
Jager, T., Crommentuijn, T., Gestel, C. A. M. van and Kooijman, S. A. L. M.
2004.
Simultaneous modelling of multiple endpoints in life-cycle toxicity tests.
Environ. Sci. Technol., 38: 2894 - 2900
Abstract
Standard toxicity tests do not allow extrapolations to the population
level, mainly because these tests apply a short, fixed exposure time
and focus on a single end point only. These limitations can be
overcome by (partial) lifecycle toxicity testing, although these test
results are harder to analyze. DEBtox is an existing software tool for
the process-based analysis of standardized bioassays, and this paper
presents two extensions of this method, making it applicable to
life-cycle tests: the simultaneous assessment of end points and the
description of aging (senescence) of the animals. We demonstrate these
adaptations by describing life-cycle tests with the springtail
Folsomia candida, exposed to cadmium and triphenyltin in their
food. The extended model is able to describe the data for all end
points simultaneously over time with few, physiologically relevant
parameters. Furthermore, the analysis reveals these chemicals to have
distinctly different modes of action: cadmium apparently decreases the
assimilation of energy from the food whereas triphenyltin increases
the maintenance costs. The model fit allows calculation of the
intrinsic rate of population increase, integrating effects on survival
and reproduction. As the analysis is process based, population
responses under food limitation can be explored, which depends
critically on the selected mode of action.