A statistical approach

Rainfall (mmH2O). 20. 40. 60. 80. 100. 120. A S O N D J F M A M J J A S. 10. 15. 20. 25 ... saving. Resting metabolism. MADAGASCAR. Tropique du Capricorne.
9MB taille 0 téléchargements 433 vues
A statistical approach Chronic food restriction and seasonal modulations of daily heterothermia and locomotor activity in a Malagasy primate: Microcebus murinus Giroud S., Blanc S., Aujard F., Bertrand F., Gilbert C., Perret M. 2007

Abiotic factors Input or energy contribution

Output or energy expenditure

Adaptive strategies

Maintenance of energy balance Survival of the individual Energy imbalance

Species survival

Madagascar: contrasted climate and habitats Habitat of rain forests Rainfall ~ 2000/4000 mm/yr Temperature ~ 24-28°c

MADAGASCAR

Habitat of dry deciduous forests Rainfall ~ 700/1200 mm/yr Temperature ~ 24-27°c

Habitat of spiny desert forests Rainfall ~ 500 mm/yr Temperature ~ 18-25°c

Tropique du Capricorne

Predictable seasonal environment

Trophic resource variability

MADAGASCAR

Rainfall (mmH2O) Minimal T °C

Resources

35

120

100

30

Cold and dry season

80

25 20

60 15 40

10

20

Tropique du Capricorne

A S

O

N D

J

F

M

A M J

J

A S

Unpredictable environment El Niño phenomenon

Rainfall (mmH2O) Resources

Minimal T °C

120

35

100

30 25

80

20 60 15 40

10

20

A S

O

N D

J

F

M

A M J

Species survival

J

Severe food shortage during several months in summer

A S

Unusual pressure during reproductive season

MADAGASCAR

Grey mouse lemur - Microcebus murinus Heterothermic primate Seasonal fattening Body mass Resting metabolism

% of variations

140 120

Energy saving

100 80 60

Tropique du Capricorne

Distribution area of Microcebus murinus

Ecological constraints

Sexual rest

Season of reproduction

Dry season

Seasonal variations of several biological parameters in percentage of the annual average

Adaptive mechanisms

Face to a chronic food shortage, what are seasonal thermo-modulation and behavioural energy-saving responses of M. murinus ?

Experimental protocol - Recording of body temperature and activity level - 12 summer-adapted male individuals Long Photoperiod (LP) Logger

- 12 winter-adapted male individuals Short Photoperiod (SP) Telemetry

Control period

Calorie restriction (CR)

2 weeks

5 weeks

Stable energy balance

40% or 80%

Daily body temperature and activity parameters Initiation time Active period

38

Hypothermia

Average Tb

100

Duration

37 60 36

Average Tb

LA

40

Minimal Tb

35

Occurrence time

20

LA 0

34

12

14

16

18

20

Dark phase

22

24 2 Hours of day

4

6

8

Light phase

10

12

Locomotor activity (a.u.)

Body temperature (°c)

80

Daily temperature and activity parameters Initiation time Active period

38

Hypothermia phase

100

37 60 36 40

Minimal Tb

35

20

0

34

12

14

16

18

20

Dark phase

22

24 2 Hours of day

4

6

8

Light phase

10

12

Locomotor activity (a.u.)

Body temperature (°c)

80

Initiation time of the hypothermia 0

- Data with large variability

Duration (min)

-60

→ Weighted moving average to highlight the general trend of the evolution

-120

-180

- Distribution not normal

-240

→ parametric tests were not applicable

-300

Body temperature (°c)

Minimal body temperature

- Non-linear evolutions

36

→ ANOVA not suitable (parametric test, linear trend) → Non-Linear General Model (NLGM) used

34 32 30 28 26 0

5

10

15

20

Time (days)

25

30

LP40 SP40 LP80 SP80

Body temperature (°c)

NLGM on Statistica

36 34 32

Effect

30

DF

Wald Stat

PP

1

1795

0.000000

CRi

1

4

0.038918

CRd

30

352

0.000000

PP*CRi

1

11

0.000812

PP*CRd

30

137

0.000000

CRi*CRd

30

11

0.999297

7

0.999998

28 26 0

5

10

15

20

25

Time (days)

LP40 SP40 LP80 SP80

General evolution in a whole model

30

Minimal Tb - test all the effects Distribution: GAMMA

PP*CRi*CRd 30

p

PP = Photoperiod (SP, LP) CRi = Calorie Restriction intensity (40%, 80%) CRd = Calorie Restriction duration (30 days)

Minimal body temperature 36

LP40

SP40

LP80

SP80

Body temperature (°c)

34

Part 1 Part 2

32

Time of rupture 30

28

26 0

5

10

12

15

20

24 25

30

Time (days)

SigmaPlot Statistical adjustment of the 2-part linear evolution

Minimal body temperature

- Significability of each slope was tested by non-parametric ANOVA of Friedman (*)

Body temperature (°c)

36 34 32

- Times of rupture and slopes were compared by nonparametric ANOVA between groups and by Mann-Whitney U-test between 2 groups in particular

30 28 26 0

5

1012 15

20

Time (days)

25

24

30

Slope 1 (°C/day)

Time of rupture (day)

Slope 2 (°C/day)

LP40

-0.13 ± 0.01*

8±2

NS → stable value 34.7 ± 0.4 °C

LP80

-0.13 ± 0.01*

24 ± 1

NS → stable value 32.9 ± 0.6 °C

SP40

-0.67 ± 0.13*

13 ± 2

NS → stable value 27.6 ± 0.8 °C

SP80

-0.74 ± 0.08*

12 ± 2

NS → stable value 27.8 ± 0.6 °C

Summary… - Biological data need statistical tools - Advanced statistical tools (NLGM) are required to explain the complexity of the biological responses

Acknowledgements - All the volunteers in this experiment… - Martine Perret and Stéphane Blanc, my PhD supervisors - The staff of Brunoy’s lab - Myriam and Frédéric Bertrand for their help in statistic analysis

Thank you for your attention !