Dynamic Energy Budget (DEB) theory by Elke, Svenja and Ben

Outline  What is DEB? Basic concepts and rules  Example: Food limitation  Toxicants in DEB  Example: increasing costs for reproduction, decreasing ingestion rate  But...  Why do we use DEB?

What is DEB? Quantitative theory; ‘first principles’ time, energy and mass balance Life-cycle of the individual links levels of organisation: molecule  ecosystems Comparison of species body-size scaling relationships; e.g., metabolic rate Fundamental to biology; many practical applications (bio)production, (eco)toxicity, climate change, … Kooijman (2010)

Why is DEB cool?

Effects on reproduction

Focus on energy budgets  Organisms must obey conservation laws for mass and energy  Reduced repro/growth must be reflected in budget  growth and reproduction are linked processes  need to understand how food is used to fuel these processes Currently, approaches based on energy budgets are the only ones to do this!

Basic rules and concepts

Energy budget … growth reproduction feeding maintenance maturation

Entire life cycle … feeding reproduction

DEB allocation rules foodfaeces reserves assimilation structure somatic maintenance  1-  maturity offspring maturity maintenance

Energy budget … growth reproduction feeding maintenance maturation 5% ad libitum

Energy budget … growth reproduction feeding maintenance maturation 50% limiting

Energy flows... foodfaeces reserves structure maturity offspring XP A = X – P S = k M V G = κ C – k M V C J = k J H R = (1 – κ) C – k J H

for embryos … reserves structure somatic maintenance  1-  maturity maturity maintenance

for juveniles … foodfaeces reserves assimilation structure somatic maintenance  1-  maturity maturity maintenance

for adults … foodfaeces reserves assimilation structure somatic maintenance  1-  gametes maturity maintenance reproduction buffer periodic release of eggs

Example: food limitation

Food limitation Jager et al. (2005)

DEB in toxicants

Toxicants in DEB external concentration (in time) toxico- kinetics toxico- kinetics internal concentration in time life-history traits one-compartment model, accounting for changes in body size

Toxicants in DEB external concentration (in time) toxico- kinetics toxico- kinetics internal concentration in time DEB parameters in time life-history traits ingestion rate maintenance rate coeff. egg costs etc. …

Toxicants in DEB external concentration (in time) toxico- kinetics toxico- kinetics internal concentration in time DEB parameters in time DEB model DEB model life-history traits

Toxicants in DEB external concentration (in time) toxico- kinetics toxico- kinetics internal concentration in time DEB parameters in time DEB model DEB model effects in time Affected DEB parameter has specific consequences for life cycle

external concentration (in time) toxico- kinetics toxico- kinetics internal concentration in time mixture toxicity Extrapolation external concentration (in time) toxico- kinetics toxico- kinetics internal concentration in time DEB parameters in time DEB model DEB model effects in time time-varying concentrations temperature food limitation

Modes of action … Standard DEBtox assimilation, maintenance, growth costs, repro costs, hazard to embryo Based on resource allocation contrasts common use (‘narcosis’, ‘uncoupling’) a MoA has a specific effect patterns on various traits effects on traits are linked!  effect on length always accompanied by effect on repro  growth affects toxicokinetics which affects toxicity  in principle, other endpoints can be included (respiration, product formation, …)

Examples

Potential targets time body length time cumulative offspring Pentachlorobenzene Alda Álvarez et al. (2006)

Potential targets foodfaeces reserves structure maturity offspring maturity maintenancesomatic maintenance assimilation  1- 

Potential targets time cumulative offspring time body length Chlorpyrifos Crommentuijn et al. (1997), Jager et al. (2007)

DEB analysis of data Simultaneous fit size and repro data MoA: decrease in ingestion rate time (days) body length time (days) cumulative offspring per female

DEB analysis of data Assume size-dependent feeding limitation (Jager et al, 2005)

What’s different? effects data individuals effects data individuals population consequences population consequences model parameters model parameters extrapolated parameters extrapolated parameters DEB-less DEB

What’s the use of DEB?  In-depth interpretation of effects on individual all endpoints over time in one framework indicates experimental ‘problems’ mechanism of action of compound  DEB is essential for inter- and extrapolation e.g., extrapolation to field conditions ‘repair’ experimental artefacts  Natural link with different population approaches simple (e.g., Euler-Lotka and matrix models) more complex (e.g., IBM’s)

But …  Strong (but explicit) assumptions are made on metabolic organisation on mechanisms of toxicity  Elaborate DEB models require strong data growth, repro and survival over (partial) life cycle e.g., Daphnia repro protocol extended with size  Almost every analysis raises more questions difficult to perform on routine basis Interesting point raised by DEB3 … hatching time and hatchling size can be affected by stress

Why do we use DEB?  Ben  Svenja  Elke

Thanks to Tjalling Jager for his nice slides! Courses International DEB Tele Course 2011 Symposia 2nd International DEB Symposium 2011 in Lisbon More information: