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Correlating impacts on life history aspects. In the context of the Dynamic Energy Budget theory. Bas Kooijman Dept of Theoretical Biology Vrije Universiteit, Amsterdam http://www.bio.vu.nl/thb/deb/. embryo. adult. juvenile. Praha, 2004/04/18. Effects on organisms. - PowerPoint PPT Presentation
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Correlating impacts on life history aspects
Bas KooijmanDept of Theoretical Biology
Vrije Universiteit, Amsterdamhttp://www.bio.vu.nl/thb/deb/
Praha, 2004/04/18
adul
t
embryo
juvenile
In the context of theDynamic Energy Budget
theory
Effects on organisms
• Process-based perspective on disturbances chemicals, temperature, parasites, noise exposure-time explicit methods (response surface)• Primary target: individuals some effects at sub-organismic level can be compensated • Effects on populations derived from individuals energy budget basic to population dynamics• Parameters of budget model individual specific and (partly) under genetic control
Concentration ranges of chemicals
• too little def: decrease in concentration comes with increase in effects• enough def: variations in concentration within this range hardly affect physiological behaviour of individuals• too much def: increase in concentration comes with increase in effects e.g. concentration of water can be too much, even for fish
no basic difference between toxic and non-toxic chemicals“too little” and “enough” can have zero range for some chemicalsImplication: lower & upper NEC for each compound
Do No Effect Concentrations exist?
Essential component: compensation at individual levelEach molecule of any compound has an effect at the molecular levelThese effects do not necessarily translate into measurable effects at the individual levelExample: removal of a kidney in a healthy human body does not result in health effects under conditions that are not extremeNEC is specific for• species and chemical compound• endpoint (survival, reproduction) one process (maintenance, reproduction, ..) is most sensitive• experimental/environmental conditions
Behaviour Energetics
DEB fouraging module: time budgeting
Fouraging: searching, feeding, digestion, food selection feeding surface area (intra-species), volume (inter-species)Sleeping: repair of damage by free radicals respiration respiration scales between surface area & volumeSocial interaction: feeding efficiency (schooling) resource partitioning (territory), parental care mate selection (gene quality energetic parameter values)Migration: traveling speed and distance: body size related spatial pattern in resource dynamics (seasonal effects) environmental constraints on reproduction
Modes of Action of Noise
Effects on reproduction• blocking out fouraging time reduction feeding efficiency• disrupting social behaviour short/long term, partner choice
Effects on survival• problems with orientation (migration)• permanent hearing damage• interaction with large-scale fishing
Effects of parasites
Many parasites increase allocation to som maintenance + growth (chemical manipulation) harvest (all) allocation to develop. + reprod.
Results larger body size higher food intake reduced reproduction
Models for toxic effects
Three model components:
• kinetics external concentration internal concentration example: one-compartment kinetics
• change in target parameter(s) internal concentration value of target parameter(s) example: linear relationship
• physiology value of parameter endpoint (survival, reproduction) example: DEB model
Kinetics
Simplest basis: one compartment kinetics
Correct for changes in • body size (growth)• lipid content (starvation)• concentration (transformation)
Dilution by growth
Note: • elimination rate decreases with length of isomorph exchange is across surface area• small changes in size already affect kinetics considerably
Dilution by growth
ke/rB ke/rB
rati
o in
tern
al/e
xter
nal c
onc
trB trB
10 10
2
1
0.5
0.1
2
1
0.5
0.1
scaled body length of daphnidscaled reproduction rate
ke elimination raterB von Bert. growth rate
Change in lipid content
Note: • biomass should be decomposed into reserve & structure• applies for slowly changing food densities only
Satiating excretion kinetics
Elimination rate satiates as function of internal concentration
Example:Removal of alcohol from blood by liver
Receptor mediated effects
• Compound knocks out functional receptors• Total amount of receptors is constant• Hazard rate linear in non-functional receptors
: no memory
Tasks of physiological module
in the specification of toxic effects of chemicals
• identify potential target parameters for toxic effects (e.g. max feeding rate, specific maintenance and growth costs) • specify interrelationships between the various physiological processes (e.g. feeding, maintenance, maturation, growth, reproduction)• quantify how endpoints depend on values of target parameters (e.g. how does cumulative number of offspring depend on the specific growth costs?)
Basic DEB scheme
food faeces
reserves
growth maturationreproduction
maturity maintenancesomatic maintenance
assimilation
1-
Modes of Action of toxicants
food faeces
reserves
growth maturationreproduction
maturity maintenancesomatic maintenance
assimilation
1-
assimilation
maintenance costs
growth costs
reproduction costs
hazard to embryo
Lethal effects: hazard rateMode of action affectstranslation to pop level
Simplest basis: Change internal conc that exceeds internal NEC
or
with
Change in target parameter
Rationale
• effective molecules operate independently
• approximation for small effects
Hazard rate
Definition: instantaneous death rate (dim: time-1)Interpretation of hazard rate times time increment: probability of death, given to be alive
Relationship with survival probability for :
Examples for :
Independent causes of death
If causes of death by events 0 are independent of that by events 1 then hazard rate add and survival probabilities multiply
Example of application: death by background mortality and by toxicant in short bioassays: background mortality is accidental which means that the hazard rate is constant
Effect on survival
Effects of Dieldrin on survival of Poecilia
killing rate 0.038 l g-1 d-1
elimination rate 0.712 d-1
NEC 4.49 g l-1
DEB-based effects on body growth
Indirect effects indicator: effects on ultimate size at constant food• decrease of assimilation rate (food intake, digestion)• increase of specific maintenance costs
Direct effects indicator: no effects on ultimate size at constant food• increase of costs for synthesis of biomass (structural)
Effect on assimilation
CuCl2 mg/kgtime, d
wei
ght1/
3 , m
g1/3
Data from Klok & de Roos 1996NEC = 4.45 mg CuCl2 /kg on Lumbricus rubellus
DEB-based effects on reproduction
Indirect effects indicator: effects on onset of reproduction• decrease of assimilation rate (food intake, digestion)• increase of specific maintenance costs• increase of costs for synthesis of biomass (structural)
Direct effects indicator: no effects on onset of reproduction• increase of costs for the synthesis of offspring• decrease of survival probability at birth
Direct effect on reproduction
time, d
cum
. # y
oung
/fem
ale
0
0.2
0.4
0.812
g Cd/l
Effect on hazardNEC = 0.023 g Cd/l
energetics
growth
maintenance
Free radicals and ageing
RespirationRespiration
Oxidative damageOxidative damage
free radicals (internally generated)
survival
feeding
tumour induction
Tumour inducing compounds
Mode of action: genotoxic compounds: similar to (natural) free radicals enhance aging non-genotoxic compounds: hamper cell-cell communicationTumour growth dynamics similar to growth of body parts -rule for allocation of resources in DEB context growth depends on: physiology via nutrition (feeding conditions) body size (age): fast growth at young age
Leeuwen, I. M. M. van 2003Mathematical models in cancer risk assessmentPhD-thesis, Vrije Universteit Amsterdam
Effect Concentration
ECx(t): Concentration that gives x% effect at exposure time t, compared to the blank
LCx(t) = ECx(t) in the case the endpoint is the survival probability (LC = lethal concentration)
Generally: ECx(t) decreases in time the pattern depends on the properties of the chemical and of the test organism
NEC = EC0()
Effects on populations
At constant food density:
At variable food density: individual-based modelling of populations requires modelling of resources
Population effects can depend on food density
Population growth of rotifer Brachionus rubens at 20˚Cfor different algal concentrations
3,4-dichloroanilinedirect effect on reproduction
potassium metavanadateeffect on maintenance
0
num
ber
of d
aphn
ids
Maintenance first
106 cells.day-1
300
200
100
01206030126
max
num
ber
of d
aphn
ids
30 35
400
300
200
100
8 11 15 18 21 24 28 32 37time, d
30106 cells.day-1
Chlorella-fed batch cultures of Daphnia magna, 20°Cneonates at 0 d: 10winter eggs at 37 d: 0, 0, 1, 3, 1, 38
Kooijman, 1985 Toxicity at population level. In: Cairns, J. (ed) Multispecies toxicity testing. Pergamon Press, New York, pp 143 - 164
Maitenance requirements:6 cells.sec-1.daphnid-1