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

somatic maintenance

assimilation

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()

Fast kinetics

Effects on survival at instantaneous equilibrium

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

Food intake at carrying capacity

103 c

ells

/dap

hnid

.d10

3 cel

ls/d

aphn

id.d

log mg V/l log mg Br/l log mg DMQ/l

log mg K2Cr2O7/l log mg AA/l log mg Col/l

9-aminoacridine colchicine

2,6-dimethylquinolinesodium bromidemetavanadate

potassium dichromate