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

Effects on reproduction

Effects on reproduction

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

repro

du

ction

DEB allocation rules

food faeces

reserves

assimilation

structure

somatic maintenance

1-

maturityoffspring

maturity maintenance

Energy budget …

growth

reproduction

feeding

maintenance

maturation5%

ad libitum

Energy budget …

growth

reproduction

feeding

maintenance

maturation50%

limiting

Energy flows...

food faeces

reserves

structure maturityoffspring

X P

A = X – P

S = kM V

G = κ C – kM V

C J = kJ H

R = (1 – κ) C – kJ H

for embryos …

reserves

structure

somatic maintenance

1-

maturity

maturity maintenance

for juveniles …

food faeces

reserves

assimilation

structure

somatic maintenance

1-

maturity

maturity maintenance

for adults …

food faeces

reserves

assimilation

structure

somatic maintenance

1-

gametes

maturity maintenance

reproductionbuffer

periodic release of eggs

Example: food limitation

Food limitation

Jager et al. (2005)

0 2 4 6 8 10 1220

30

40

50

60

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90

100

time (d)

bo

dy

len

gth

(µ

m)

0 2 4 6 8 10 1220

30

40

50

60

70

80

90

100

time (d)

bo

dy

len

gth

(µ

m)

H

M

L

0 2 4 6 8 10 120

20

40

60

80

100

120

140

160

time (d)

cum

ula

tive

nu

mb

er o

f eg

gs

0 2 4 6 8 10 120

20

40

60

80

100

120

140

160

time (d)

cum

ula

tive

nu

mb

er o

f eg

gs

H

M

L

DEB in toxicants

Toxicants in DEB

externalconcentration

(in time)

toxico-kinetics

toxico-kinetics internal

concentrationin time

life-historytraits

one-compartment model, accounting for changes in body size

Toxicants in DEB

externalconcentration

(in time)

toxico-kinetics

toxico-kinetics internal

concentrationin time DEB

parametersin time

life-historytraits

ingestion ratemaintenance rate coeff.egg costsetc. …

Toxicants in DEB

externalconcentration

(in time)

toxico-kinetics

toxico-kinetics internal

concentrationin time DEB

parametersin time

DEBmodel

DEBmodel

life-historytraits

Toxicants in DEB

externalconcentration

(in time)

toxico-kinetics

toxico-kinetics internal

concentrationin time DEB

parametersin time

DEBmodel

DEBmodel effects

in time

Affected DEB parameter has specific consequences for life cycle

externalconcentration

(in time)

toxico-kinetics

toxico-kinetics internal

concentrationin time

mixture toxicity

Extrapolation

externalconcentration

(in time)

toxico-kinetics

toxico-kinetics internal

concentrationin time DEB

parametersin time

DEBmodel

DEBmodel 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

bo

dy len

gth

time

cum

ulative o

ffsprin

g

Pentachlorobenzene

Alda Álvarez et al. (2006)

Potential targets

food faeces

reserves

structure maturityoffspring

maturity maintenancesomatic maintenance

assimilation

1-

Potential targets

time

cum

ulative o

ffsprin

g

time

bo

dy len

gth

Chlorpyrifos

Crommentuijn et al. (1997), Jager et al. (2007)

DEB analysis of data

Simultaneous fit size and repro data

MoA: decrease in ingestion rate

0 50 100 1501

2

3

4

5

6

7

8

9

time (days)

body leng

th

80120160200

0 50 100 1500

5

10

15

20

25

30

35

40

time (days)

cumulative o

ffspring per female

80120160200

DEB analysis of data

Assume size-dependent feeding limitation (Jager et al, 2005)

0 50 100 1501

2

3

4

5

6

7

8

9

time (days)

body leng

th

0 50 100 150

0

5

10

15

20

25

30

35

40

time (days)

cumulative o

ffspring per female

80120160200

80120160200

What’s different?

effectsdata individuals

effectsdata individuals

populationconsequences

populationconsequences

modelparameters

modelparameters

extrapolatedparameters

extrapolatedparameters

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: http://www.bio.vu.nl/thb