dynamic energy budget (deb) theory by elke, svenja and ben
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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
70
80
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