Fig 1.
The temperature treatments depicted as temperature as a function of time over 24h.
Five constant temperatures (8, 12, 16, 18 and 20°C, solid lines), three temperature ranges with an amplitude of ± 4° around average temperatures of 12°C (black circles, black line), 16°C (grey circle, grey line) and 20°C (white circle, broken line) and one with an amplitude of ± 8°C from the average (black triangles, dotted line) were used. Temperatures were shifted with 4°C per hour. All treatments were run with the minimum and maximum temperature around 12 a.m. and 12 p.m., respectively.
Table 1.
Equations for the basic DEBkiss model.
Table 2.
Parameters of the DEBkiss model as used in this study.
The fixed parameters were retrieved from Jager et al (2014) and were the same for all parameter fits. The fitted parameters are given for the three scenarios: 1) All constant temperature data (minus 8°C) are described jointly using the Arrhenius temperature and 20°C as a reference, 2) The constant 16°C and the variable 16±8°C treatments are described together applying a stress factor (s) on the somatic maintenance rate and 3) The 16°C treatment is described in the presence of the three highest Cu concentrations applying a Cu-related stress factor (sCu, Table 1) on maximum assimilation rate (JaAm) and length at puberty (Lp). Parameter estimates are given ± s.d.
Fig 2.
Temperature effect on five different endpoints: final brood size (A), Final body length (B), time to first egg (C), lifespan (D) and Population Growth Rate (PGR) (E).
All data are given as a function of the mean temperature of the treatment. Data are given as mean ± s.e.m., apart from PGR which is given with 95% Confidence Intervals (CI) obtained by bootstrapping. Significantly different treatments (ANOVA followed by a Tukey post hoc test) are denoted by different letters. Constant temperature treatments are given in black symbols, treatments varying ± 4°C are given in grey symbols and treatments varying ± 8°C are given in open symbols.
Fig 3.
Temperature effects on traits fitted using the DEBkiss model.
The development of body length (A) and offspring production (B) as a function of time for the five constant temperature treatments are described by the DEBkiss model including a temperature function (R2 = 0.87). Fig C and D shows bodylength and offspring production as a function of time for the constant 16°C treatment and the variable 16 ± 8°C treatment described by the DEBkiss model including an 8% increase in mainainance cost for the variable treatment (R2 = 0.87). Data are given as mean ± s.e.m. Model parameters are shown in Table 2.
Fig 4.
The effects of Cu exposure on traits responses in C. elegans in treatments with an average temperature of 16°C.
The five different endpoints: Final brood size (A), final body length (A), time to first egg (B), lifespan (D) and Population Growth Rate (PGR) (E) for the constant 16°C treatment (filled symbols), the 16 ± 4°C (grey symbols) and the 16 ± 8°C (open symbols) as a function of Cu concentrations in the agar. Data are given as mean ± s.e.m. and are described with a three parameter log-logistic concentration response model, except for TFE. The parameters are given in Table 3, together with the concentration-response parameters of the other temperature treatments.
Table 3.
Dose-response parameters (Eq 1) for the measured endpoints: Length increase (Maximum length minus length at hatching), lifespan, brood size and population growth rate (PGR) for the different temperature treatments.
The curves for the three treatments with an average temperature of 16°C are shown in Fig 3. Data for the 12°C and 24°C average temperature treatments are presented in S2 and S3 Figs. The parameters are given ±SE.
Fig 5.
Copper exposure effects on traits fitted using the DEBkiss model.
The development of body length (A) and offspring production (B) as a function of time for the 16°C constant treatment combined with 0, 8, 20 and 40 mg Cu L-1 described by the DEBkiss model. Fits include a Cu-related stress factor (sCu, Table 1) on maximum assimilation rate (JaAm) and length at puberty (Lp) (R2 = 0.97). A mixed stressor prediction including the 8% increase in somatic maintainance obtained when fitting the constant and variable control treatments together, and the Cu-related stress factor ontained from the constant temperature treatment (A, B) is shown together with the body length (C) and offspring production (D) data from the 16 ± 8°C treatment combined with 0, 8, 20 and 40 mg Cu L-1. Jointly the mixed stressor prediction describes 75% of the variation in the data. The 1 and 3 mg Cu L-1 data are omitted from the fit, as they increased offspring production, which the DEBkiss model is not parameterised to deal with. Data are presented as mean ± s.e.m.