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Chemical (and other) stress in DEB 5: extrapolations. Tjalling Jager Dept. Theoretical Biology. TexPoint fonts used in EMF. Read the TexPoint manual before you delete this box.: A A A A A A A. Contents. Extrapolations Why extrapolation? Examples of extrapolation. Why extrapolation.

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chemical and other stress in deb 5 extrapolations

Chemical (and other) stress in DEB5: extrapolations

Tjalling Jager

Dept. Theoretical Biology

TexPoint fonts used in EMF.

Read the TexPoint manual before you delete this box.: AAAAAAA

contents
Contents

Extrapolations

  • Why extrapolation?
  • Examples of extrapolation
why extrapolation
Why extrapolation

“Protection goal”

Available data

??

  • different exposure time
  • different temperature
  • different species
  • time-varying exposure
  • species interactions
  • populations
  • other stresses
  • mixture toxicity
contents1
Contents

Example life-cycle dataset

  • Bindesbøl et al (2007), re-analysed in Jager and Klok (2010)
  • copper in Dendrobaena octaedra
  • size, survival, cocoons over 20 weeks
  • here, only [Cu] > 80 mg/kg
deb analysis of data
40

9

35

8

30

7

25

6

cumulative offspring per female

20

5

body length

15

4

10

3

5

2

0

0

50

100

150

1

time (days)

0

50

100

150

time (days)

DEB analysis of data

Assumption

  • copper leads to a decrease in ingestion rate

80

80

120

120

160

160

200

200

Jager and Klok, 2010

parameter estimates
internal

concentration

in time

DEB

parameters

in time

external

concentration

(in time)

Parameter estimates

TK pars

tox pars

DEB pars

toxico-

kinetics

DEB

model

life-history

traits

to population model …

population effects
Population effects
  • Type of information that risk assessors should be most interested in ...
  • Popular endpoints
    • intrinsic rate of increase
    • toxicant concentration where this rate is zero
    • (or multiplication factor lambda, and where it is one)
  • Popular (simple) approaches
    • matrix models
    • Euler-Lotka equation
    • ...
matrix models
Matrix models
  • In combination with DEB(tox)
    • Klok & De Roos (1996), Lopes et al (2005), Klanjscek et al (2006), Smit et al (2006), Liao et al (2006)
  • Discrete time and discrete stages ...
    • one state variable (size or age) for the organism …
    • DEB generally requires more ...

1

2

3

4

euler lotka equation
Euler-Lotka equation
  • In combination with DEB(tox)
    • Kooijman & Metz (1984), Jager et al (2004), Alda Álvarez et al (2005, 2006) ...
  • Continuous time and continuous states ...
    • straightforward for DEB animals
    • only for constant environment ...
  • In constant environment, populations grow exponentially
individual based models
Individual-based models
  • Follow all individuals seperately …
  • Full flexibility for dynamic environments
    • but calculation intensive …
    • see Martin et al (subm.)

Kooijman (2000)

population effects1
no-effectsPopulation effects

But, this is extinction at:

  • abundant food
  • no predation
  • no disease
  • optimal temperature
  • low competition

0.025

0.02

0.015

population growth rate (d-1)

0.01

0.005

0

60

80

100

120

140

160

180

200

concentration (mg/kg soil)

Jager and Klok, 2010

extrapolation food
internal

concentration

in time

DEB

parameters

in time

external

concentration

(in time)

Extrapolation: food

TK pars

tox pars

DEB pars

toxico-

kinetics

DEB

model

life-history

traits

less food in environment

energy budget
feeding

5%

reproduction

maturation

maintenance

Energy budget …

ad libitum

growth

energy budget1
reproduction

50%

maintenance

Energy budget …

feeding

limiting

maturation

growth

food limitation 90
Food limitation (90%)

40

9

35

8

30

7

25

6

cumulative offspring per female

20

5

body length

15

4

10

3

5

2

0

0

50

100

150

1

time (days)

0

50

100

150

time (days)

80

80

120

120

160

160

200

200

food limitation
Food limitation

0.025

0.02

food 100%

0.015

population growth rate (d-1)

0.01

food 90%

0.005

0

60

80

100

120

140

160

180

200

concentration (mg/kg soil)

Jager and Klok, 2010

extrapolation chemicals
internal

concentration

in time

DEB

parameters

in time

external

concentration

(in time)

Extrapolation: chemicals

TK pars

tox pars

DEB pars

toxico-

kinetics

DEB

model

life-history

traits

other compounds (related)

process based qsar
Process-based QSAR

Jager and Kooijman, 2009

extrapolation mixtures
internal

concentration

in time

internal

concentration

in time

DEB

parameters

in time

external

concentration

(in time)

external

concentration

(in time)

toxico-

kinetics

Extrapolation: mixtures

TK pars

tox pars

DEB pars

toxico-

kinetics

DEB

model

life-history

traits

other compounds (mixtures)

mixtures
internal

concentration

A in time

internal

concentration

B in time

DEB

parameters

in time

external

concentration

B (in time)

external

concentration

A (in time)

Mixtures

toxico-

kinetics

growth

DEB

model

toxico-

kinetics

life-history

traits

theory implies interactions …

mixtures1
internal

concentration

A in time

internal

concentration

B in time

DEB

parameters

in time

external

concentration

A (in time)

external

concentration

B (in time)

Mixtures

??

toxico-

kinetics

DEB

model

toxico-

kinetics

life-history

traits

simple mixture rules
compound

‘target’

metabolic process

assimilation

maintenance

Simple mixture rules

toxicity parameters linked (compare CA)

simple mixture rules1
Simple mixture rules

compound

‘target’

metabolic process

assimilation

maintenance

simple mixture rules2
Simple mixture rules

compound

‘target’

metabolic process

assimilation

maintenance

toxicity parameters independent (compare IA)

visual representation
Visual representation
  • For binary mixture, model represents surface that changes in time …

Baas et al (2007)

pahs in daphnia
fluoranthene

pyrene

PAHs in Daphnia
  • Based on standard 21-day OECD test
    • 10 animals per treatment
    • length, reproduction and survival every 2 days
    • no body residues (TK inferred from effects)

Jager et al (2010)

slide27
same target

costs reproduction

(and costs growth)

iso effect lines
Iso-effect lines

for body length <50% effect

extrapolation species
internal

concentration

in time

DEB

parameters

in time

external

concentration

(in time)

Extrapolation: species

?

TK pars

tox pars

DEB pars

toxico-

kinetics

DEB

model

life-history

traits

other (related) species

experiments nematodes
Experiments nematodes

Species

  • Caenorhabditis elegans and Acrobeloides nanus

Chemicals

  • cadmium, pentachlorobenzene and carbendazim

Exposure

  • in agar

Endpoints

  • survival, body size, reproduction over full life cycle
  • analysed with extended DEBtox

Studies published as: Alda Álvarez et al.,

2005 (Func. Ecol.), 2006 (ES&T), 2006 (ET&C)

pecb in a nanus
A. nanusPeCB in A. nanus

Effects on assimilation

pecb in c elegans
C. elegansPeCB in C. elegans

Costs for growth and reproduction

species differences
toxicant

target site

toxicant

target site

maintenance

maintenance

reproduction

reproduction

Species differences?

Species A

Species B

species differences1
Species differences?

toxicant

target site

maintenance

reproduction

extrapolation exposure
internal

concentration

in time

metabolic

processes

in time

external

concentration

(in time)

Extrapolation: exposure

TK pars

tox pars

DEB pars

toxico-

kinetics

DEB

model

life-history

traits

time-varying concentrations

time varying exposure
Time-varying exposure

Specifically relevant for risk assessment

  • Such as:
    • accidental spills
    • plant-protection products
    • industrial chemicals; batch production
  • Impractical and costly to test each scenario experimentally
time varying exposure2
environ. conc.

time

time

Time-varying exposure

Assumption

  • toxicokinetics follows first-order, one-comp. model

internal conc.

time varying exposure3
environ. conc.

NEC

time

time

Time-varying exposure

Assumption

  • effects on energetic processes are reversible

blank value

assimilation eff.

internal conc.

experimental validation
Experimental validation

Daphnia magna and fenvalerate

  • modified 21-day reproduction test
  • pulse exposure for 24 hours
  • two (more or less) constant food levels

Pieters et al (2006)

pulse exposure
Body length

Cumulative offspring

Fraction surviving

High food

Low food

Pulse exposure

mode of action: ‘assimilation’

  • Insights
  • tox. parameters independent of food
  • chemical effects fully reversible
  • reproduction rate slows down …
summary
Summary
  • Extrapolation is crucial for environmental management
    • extrapolation requires mechanistic theory
    • DEB provides a framework for extrapolation
  • But, hypotheses for toxicant effects must be ‘correct’
  • More work is needed, e.g.,
    • starvation responses and interaction with toxicants
    • patterns in DEB parameter values between species
    • patterns in toxicity parameters (species and chemicals)
    • reversibility of toxic effects
    • interactions between chemicals in a mixture
    • etc. etc. ...
outlook
biochemistry

DEB theory

species specific

Outlook
  • number of chemicals and species is very large …
  • but number of target sites and DEB parameters is limited!

toxicant

target site

DEB

parameters

DEB

model

?

effect on

life cycle

slide50
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Vacancies

  • PhD position at SCK-CEN in Mol (Belgium): radiation effects on duckweed (Lemna minor) with DEB

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

And:http://www.bio.vu.nl/thb/users/tjalling/debtox_papers.htm

Also, check out: http://cream-itn.eu/

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