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The stress physiology of
extended duration tonic
immobility in the juvenile
lemon shark, Negaprion
brevirostris (Poey 1868...
Outline
• 1. Introduction
• 2. Methods
• 3. Results
• 4. Discussion
2
1. Introduction
• 1.1 Definitions
• 1.2 Aim of experiment
3
1.1 Definitions
• Negaprion brevirostris (Poey 1868)
4
1.1 Definitions
• In buccal pumping, water circulates through
the gills as a result of the contraction of buccal
muscles.
...
1.1 Definitions
• Tonic immobility is a reversible coma-like
stasis, resulting in absence of motion and mental
stupor.
• I...
1. Introduction
• 1.1 Definitions
• 1.2 Aim of experiment
7
1.2 Aim of experiment
• A limp muscle tone and deep rhythmical
ventilations were observed.
• Tonic immobility is assumed t...
Outline
• 1. Introduction
• 2. Methods
• 3. Results
• 4. Discussion
9
2. Methods
• 2.1 Animal collection
• 2.2 Experimental design
• 2.3 Parameters measured
• 2.4 Data analysis
10
2.1 Animal collection
• 8 juvenile lemon sharks were captured using
conventional hook-and-line angling gear, in the
mangro...
2.1 Animal collection
• During transportation to laboratory, sharks were
put in a 200 L cooler of seawater.
• 50% of the w...
2. Methods
• 2.1 Animal collection
• 2.2 Experimental design
• 2.3 Parameters measured
• 2.4 Data analysis
13
2.2 Experimental design
• In this experiment, and for this species, tonic
immobility (TI) was induced by rapid
dorsoventra...
2.2 Experimental design
• 2 variables were taken into account:
• Presence or absence of a prolonged TI
• Presence or absen...
2.2 Experimental design
• Blood samples of 1 mL were drawn by caudal
venipuncture at 0, 30, 90, and 180 minutes of
each tr...
2. Methods
• 2.1 Animal collection
• 2.2 Experimental design
• 2.3 Parameters measured
• 2.4 Data analysis
17
2.3 Parameters measured
• Blood chemistry:
• Whole blood
• pH
• Carbon dioxide
• Bicarbonate
• Lactate
• Glucose
• Plasma
...
2.3 Parameters measured
• Behavioral observations of respiration:
• Buccal pumping was evaluated by the number of
contract...
2. Methods
• 2.1 Animal collection
• 2.2 Experimental design
• 2.3 Parameters measured
• 2.4 Data analysis
20
2.4 Data analysis
• pH, pCO2 and lactate analysis was done using
the iStat point of care device.
• Glucose analysis was do...
2.4 Data analysis
• Data were analysed using RM-MANOVA,
which stands for repeated measures
multivariate analysis of varian...
Outline
• 1. Introduction
• 2. Methods
• 3. Results
• 4. Discussion
23
3. Results
• 3.1 Blood chemistry
• 3.2 Behavioural observations
24
3.1 Blood chemistry
• Tonic immobility had statistically significant
effects on a number of blood parameters.
• Exhaustive...
3.1 Blood chemistry
• RM-MANOVA results for effects of TI and
exercise on whole blood and plasma chemistry
in the juvenile...
3.1 Blood chemistry
• Variation in carbon dioxide levels
Tonic immobility Exhaustive exercise
27
3.1 Blood chemistry
• Variation in blood pH
Tonic immobility Exhaustive exercise
28
3.1 Blood chemistry
• Variation in lactate levels
Tonic immobility Exhaustive exercise
29
3.1 Blood chemistry
• Variation in glucose levels
Tonic immobility Exhaustive exercise
30
3.1 Blood chemistry
• Plasma electrolytes were significantly disrupted
in sharks maintained in TI compared to those
which ...
3. Results
• 3.1 Blood chemistry
• 3.2 Behavioural observations
32
3.2 Behavioural observations
Buccal pumping rate (contraction/min)
Time (min) Control 0 30 90 180
Exercise 32.5 39.0 39.5 ...
Outline
• 1. Introduction
• 2. Methods
• 3. Results
• 4. Discussion
34
4. Discussion
• The results demonstrate that tonic immobility is
a very stressful experience:
• Inefficient ventilation Bl...
4. Discussion
• Tonic immobility is a respiratory challenge for
the juvenile lemon sharks.
• In response, sharks are able ...
The stress physiology of extended duration tonic immobility in the juvenile lemon shark, Negaprion brevirostris (Poey 1868)
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The stress physiology of extended duration tonic immobility in the juvenile lemon shark, Negaprion brevirostris (Poey 1868)

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This presentation describes the findings of the reference below on the physiological effects of tonic immobility on juvenile lemon sharks.
Publication authors:
Edward J. Brooks et al., Journal of Experimental Marine Biology and Ecology, 2011
Presentation author:
Nour Salam

Published in: Science
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The stress physiology of extended duration tonic immobility in the juvenile lemon shark, Negaprion brevirostris (Poey 1868)

  1. 1. The stress physiology of extended duration tonic immobility in the juvenile lemon shark, Negaprion brevirostris (Poey 1868) Edward J. Brooks et al., Journal of Experimental Marine Biology and Ecology, 2011
  2. 2. Outline • 1. Introduction • 2. Methods • 3. Results • 4. Discussion 2
  3. 3. 1. Introduction • 1.1 Definitions • 1.2 Aim of experiment 3
  4. 4. 1.1 Definitions • Negaprion brevirostris (Poey 1868) 4
  5. 5. 1.1 Definitions • In buccal pumping, water circulates through the gills as a result of the contraction of buccal muscles. • In ram ventilation, water circulates through the gills as a result of swimming. • Lemon sharks rely mainly on ram ventilation, but can supplement it with buccal pumping. 5
  6. 6. 1.1 Definitions • Tonic immobility is a reversible coma-like stasis, resulting in absence of motion and mental stupor. • It can be caused by the presence of a predator, or by the necessity for reproduction. • It is used by scientists to safely handle sharks. • Terrestrial animals will have stiff, rigid muscles. • Sharks will have relaxed, limp muscles. 6
  7. 7. 1. Introduction • 1.1 Definitions • 1.2 Aim of experiment 7
  8. 8. 1.2 Aim of experiment • A limp muscle tone and deep rhythmical ventilations were observed. • Tonic immobility is assumed to be of benign effect on elasmobranchs. • Little research was done on the effects of tonic immobility in elasmobranchs. • Our aim is to investigate the physiological and behavioural effects of prolonged tonic immobility on the juvenile lemon shark. 8
  9. 9. Outline • 1. Introduction • 2. Methods • 3. Results • 4. Discussion 9
  10. 10. 2. Methods • 2.1 Animal collection • 2.2 Experimental design • 2.3 Parameters measured • 2.4 Data analysis 10
  11. 11. 2.1 Animal collection • 8 juvenile lemon sharks were captured using conventional hook-and-line angling gear, in the mangrove forests of The Bahamas. 4 ♂ and 4 ♀ 11
  12. 12. 2.1 Animal collection • During transportation to laboratory, sharks were put in a 200 L cooler of seawater. • 50% of the water was replaced by fresh seawater every 5 minutes. • Sharks were then housed individually in 13,000L circular tanks, and fed daily with tuna or sardines. • Temperature, salinity and dissolved oxygen were monitored during the experiment. 12
  13. 13. 2. Methods • 2.1 Animal collection • 2.2 Experimental design • 2.3 Parameters measured • 2.4 Data analysis 13
  14. 14. 2.2 Experimental design • In this experiment, and for this species, tonic immobility (TI) was induced by rapid dorsoventral inversion. 14
  15. 15. 2.2 Experimental design • 2 variables were taken into account: • Presence or absence of a prolonged TI • Presence or absence of an initial exhaustive exercise • 4 treatments of 3 hours consist of all the combinations: • No initial exercise, prolonged TI • Initial exercise, prolonged TI • No initial exercise, TI only at blood samples • Initial exercise, TI only at blood samples 15
  16. 16. 2.2 Experimental design • Blood samples of 1 mL were drawn by caudal venipuncture at 0, 30, 90, and 180 minutes of each treatment. • Each of the 8 sharks was subjected to all 4 different treatments in a random order. • Tank depth was lowered prior to any treatment. • A resting period of 4 days was set between each treatment. 16
  17. 17. 2. Methods • 2.1 Animal collection • 2.2 Experimental design • 2.3 Parameters measured • 2.4 Data analysis 17
  18. 18. 2.3 Parameters measured • Blood chemistry: • Whole blood • pH • Carbon dioxide • Bicarbonate • Lactate • Glucose • Plasma • Magnesium • Sodium • Potassium • Calcium • Chloride • Urea 18
  19. 19. 2.3 Parameters measured • Behavioral observations of respiration: • Buccal pumping was evaluated by the number of contraction of buccal chamber per minute. Treatments with prolonged TI • Ram ventilation was evaluated by the number of tail beat cycles per minute. Treatments with TI only at blood samples • Control values were taken during the rest periods between treatments. 19
  20. 20. 2. Methods • 2.1 Animal collection • 2.2 Experimental design • 2.3 Parameters measured • 2.4 Data analysis 20
  21. 21. 2.4 Data analysis • pH, pCO2 and lactate analysis was done using the iStat point of care device. • Glucose analysis was done using Accu-Check glucose meter. • Plasma sodium and potassium were quantified using a flame photometer. • Plasma urea, chloride, magnesium and calcium were quantified using BioAssay kits. 21
  22. 22. 2.4 Data analysis • Data were analysed using RM-MANOVA, which stands for repeated measures multivariate analysis of variance. • The level of significance α for all test was 5%. 22
  23. 23. Outline • 1. Introduction • 2. Methods • 3. Results • 4. Discussion 23
  24. 24. 3. Results • 3.1 Blood chemistry • 3.2 Behavioural observations 24
  25. 25. 3.1 Blood chemistry • Tonic immobility had statistically significant effects on a number of blood parameters. • Exhaustive exercise had statistically significant effects on a number of blood parameters. • However, there was no combined effect of TI and exercise. • Lemon sharks presented considerable individual variation in blood parameters. 25
  26. 26. 3.1 Blood chemistry • RM-MANOVA results for effects of TI and exercise on whole blood and plasma chemistry in the juvenile lemon shark. 26
  27. 27. 3.1 Blood chemistry • Variation in carbon dioxide levels Tonic immobility Exhaustive exercise 27
  28. 28. 3.1 Blood chemistry • Variation in blood pH Tonic immobility Exhaustive exercise 28
  29. 29. 3.1 Blood chemistry • Variation in lactate levels Tonic immobility Exhaustive exercise 29
  30. 30. 3.1 Blood chemistry • Variation in glucose levels Tonic immobility Exhaustive exercise 30
  31. 31. 3.1 Blood chemistry • Plasma electrolytes were significantly disrupted in sharks maintained in TI compared to those which were not. Plasma Mg, Na, Ca were elevated. Plasma K was depressed. Plasma Cl and urea were not affected. • Exhaustive exercise did not have any significant effect on plasma electrolytes. 31
  32. 32. 3. Results • 3.1 Blood chemistry • 3.2 Behavioural observations 32
  33. 33. 3.2 Behavioural observations Buccal pumping rate (contraction/min) Time (min) Control 0 30 90 180 Exercise 32.5 39.0 39.5 40.5 41.3 No exercise 32.5 38.2 38.0 39.5 41.0 Ram ventilation rate (tail beat cycle/min) Time (min) Control 0 30 90 180 Exercise 63 83 64 69 72 No exercise 63 78 74 72 66 33
  34. 34. Outline • 1. Introduction • 2. Methods • 3. Results • 4. Discussion 34
  35. 35. 4. Discussion • The results demonstrate that tonic immobility is a very stressful experience: • Inefficient ventilation Blood acidosis • Corticosteroids cascade Electrolyte balance disruption • Glucocorticoid hormone Hyperglycemic response • Compensatory mechanisms Increase in ventilation rate 35
  36. 36. 4. Discussion • Tonic immobility is a respiratory challenge for the juvenile lemon sharks. • In response, sharks are able to implement compensatory mechanisms: central neural processing is intact. • This technique should be used with care and with supplemental ventilation. • Research on shark repellents should take this into consideration. 36

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