Diving Physiology and Behavior

Transcription

1 Diving Physiology and Behavior

2 Fundamental Constraint on Foraging Behavior Return to Surface to Breathe

3 Studies of Dive Behavior Dive depths from entanglements Observations Electronic developments instruments to measure diving

4 0 Sea otter Walrus Marine Mammal Diving Depths Otariids Phocids Odontocetes Mysticetes Dive depth (m) Average Depth Max Depth

5 Diving Physiology I. Pressure effects II. Pressure diseases III. Breath hold diving

6 Pressure Effects Hydrostatic pressure pressure at depth due to weight of water column

7 Hydrostatic Pressure Depth (m) Pressure (Atms) Surface Harbor seals, CA sea lions Elephant seals Sperm whales, beaked whales

8 Pressure Effects Hydrostatic pressure pressure at depth due to weight of water column Boyle's Law How pressure changes as function of depth Lung Collapse

9 Boyle s Law V 1 = P 2 V 2 P 1 P V V 1 P 1 = V 2 P 2

10 Change in Volume with Pressure 1/2 1/3 1/4

11 Lung Collapse Graded process m in all marine mammals

12 How Do Marine Mammals Deal With Lung Collapse? 1) Reinforced terminal airways & trachea - cartilage and muscle reinforcement

13 Lung collapse begins at alveoli and works up

14 Phocid Otariid Odobenid

15 How Do Marine Mammals Deal With Lung Collapse? 1) Reinforced terminal airways & trachea - cartilage and muscle reinforcement 2) Lung surfactants - reduces surface tension - produced in alveoli

16 Diving Physiology I. Pressure effects II. Pressure diseases III. Breath hold diving

17 Pressure Diseases Henry s law: pressure = solubility of gas in blood & tissues 1) N 2 narcosis Narcotic affect on CNS Humans: onset ~30m, loss of consciousness ~ 100m 2) O 2 toxicity - Toxic at high pressures - Causes: nausea, convulsion, death

18 Nitrogen Absorption

19 Field Measurement of Lung Collapse Weddell Seals

20 Dolphins trained to do repetitive dives Sampled blood Build up of N 2 occurred

21 Pressure Diseases 3) Decompression sickness Increase solubility at depth Gases saturated in tissues Form bubbles in tissue/joints on ascent

22 Pressure Diseases 3) Decompression sickness Increase solubility at depth Gasses saturated in tissues Form bubbles in tissue/joints on ascent 4) High pressure nervous syndrome (HPNS) Pressure causes changes in nerve function Cause tremors, seizures, and death

23 Direct Effects of Pressure 1) May change protein structure and function 2) Change enzyme kinetics 3) May influence viscosity of cell membranes

24 Adaptations to Pressure Deep Divers Dive on exhalation(?) Lung collapse Avoid O 2 toxicity N 2 narcosis? HPNS?? N 2 retention Pressure Squeeze Eliminate air spaces Shallow Divers Dive on inhalation Dive repetitively Decompression sickness Possible, Avoidance? Pressure Squeeze Eliminate air space

25 Diving Physiology I. Pressure effects II. Pressure diseases III. Breath hold diving

26

27 Marine Mammal Dive Duration 100 Average Maximum Dive duration (minutes) 10 1 Sea otter Sirenia Walrus Otariids Phocids Odontocetes Mysticetes

28 Breath Hold Diving Storing oxygen on board Lungs Muscle Blood Reduce oxygen usage Aerobic vs. Anaerobic metabolism

29 Early Studies Forced breath-hold experiments

30

31 Dive Response Extreme bradycardia Few beats per min Cardiac Output by up 90% Dramatic peripheral vasoconstriction Flow to heart lung and brain Muscles, GI tract, and other organs reduced Hypometabolism End of dive spike of lactic acid

32 Physiological Changes from Forced Dive

33 Breath Hold Diving Storing oxygen on board Lungs Muscle Blood Reduce oxygen usage Aerobic vs. Anaerobic metabolism

34

35

36 Increased O 2 Stores Lung O 2 stores Reduced in deep divers Important in shallow divers

37 Increased O 2 Stores Lung O 2 stores Reduced in deep divers Important in shallow divers Higher muscle O 2 Myoglobin: oxygen binding protein in muscle, similar to hemoglobin

38 Myoglobin in relation to dive times

39 Myoglobin in relation to dive duration

40 Increased O 2 Stores Lung O 2 stores Reduced in deep divers Important in shallow divers Higher muscle O 2 Myoglobin Higher Blood O 2 Larger blood volume Higher hematocrit Higher blood hemoglobin

41

42 Changes in the Distribution of Blood During Diving

43

44 Spleen contraction Increases circulating red blood cells (hematocrit)

45

46 Breath Hold Diving Storing oxygen on board Lungs Muscle Blood Reduce oxygen usage Aerobic vs. Anaerobic metabolism

47 Decrease Metabolism 1) body size

48 Larger animals use less energy per unit mass :1 ratio 700 Oxygen stores 600 scale to 1.0 Metabolic rate (Watts) Metabolic rate kg 0.75 Oxygen stores kg Oxygen stores (Liters) Mass (kg)

49 Decrease Metabolism 1) body size 2) Swim efficiently, streamlining

50 Decrease Metabolism 1) body size 2) Swim efficiently, streamlining 3) Hypometabolism Vasoconstriction & redistribution of blood 50% of resting metabolism costs due to organs

51 Redistribution of Blood Flow

52 Decrease Metabolism 1) body size 2) Swim efficiently, streamlining 3) Hypometabolism Vasoconstriction & redistribution of blood 50% of resting metabolism costs due to organs Increased tolerance to hypoxia Bradycardia

53 Comparison of diving bradycardia in several species

54 Is The Dive Response Real? Forced dives No control over duration Maximum response (Fear) Natural dives Animals control duration, effort, oxygen use Graded response

55 Bradycardia

56 Field Studies

57

58

59

60 Breath Hold Diving Storing oxygen on board Lungs Muscle Blood Reduce oxygen usage Aerobic vs. Anaerobic metabolism

61 Biochemical Pathway of Metabolism Aerobic - Oxygen present - Produces ATP Anaerobic - No oxygen - Produces only 2 ATP - Lactic acid produced

62 Aerobic Dive Limit (ADL): Amount of time an animal can hold its breath without an increase in lactic acid cadl (min) = O 2 stores (ml O 2 kg -1 ) Metabolic Rate (ml O 2 kg -1 min -1 )

63 Aerobic Dive Limit Phylogenetic differences: O 2 stores Diving Metabolic Rate Dive depths & durations

64 Aerobic Dive Limit Phylogenetic Differences Phocids Superb O 2 stores (60 ml O 2 kg -1 ) Low diving metabolic rate (1-2 x BMR) Otariids & Dolphins Good O 2 stores (40 ml O 2 kg -1 ) High diving metabolic rate (4-7 x BMR)

65 25 Role of Body Mass on Dive Time Phocids 1.4 x BMR Aerobic dive limit (minutes) Phocids 2 x BMR Otariids 5 x BMR Dolphins 5 x BMR Body mass (kg)

66 Is The Dive Response Real? Forced dives No control over duration Maximum response (Fear) Natural dives Animals control duration, effort, oxygen use Graded response

67 Leptonychotes weddelli- Weddell seal

68 Weddell Seals on Fast Ice

69

70

71 Repeated blood, heart-rate, & metabolism measurements

72

73 McMurdo Sound 1977

74 Catching a Weddell seal

75

76 Dives less than 20 minutes No increase blood lactic acid Dives exceeding 20 min Postdive increase in blood lactate Increased with dive duration Dives less than 20 minutes Aerobic metabolism Within aerobic dive limit (ADL)

77 Comparison of postdive blood lactate concentration after forced submersions and natural dives Long natural dive Forced submersion Natural dives

78 Time-depth recorders (TDRs) were also deployed on freeranging seals in McMurdo Sound to determine the normal dive duration and depth. Kooyman-Billups TDR

79 Free-ranging Weddell seal TDR record

80 Dives from isolated hole Free-ranging dives

81 ADL 90-95% of all dives < 20 min

82

83 Ice Hole Experiments Dive response is graded Estimates of O 2 stores & cadl matched lactate measurements Most animals dive within estimated ADL More efficient diving strategy

84 Decrease in Lactic Acid with Time at Surface

85 20 min aerobic dive with 2 minute surface interval

86 20 min aerobic dive with 2 minute surface interval min anaerobic dive with 100 minute surface interval

87 Why Dive Anaerobically? Can reach deeper depths Untapped resources Larger prey More continuous time at depth More time for pursuit Handling time

88 Understanding Diving Patterns in Nature

89 60 Relationship between O2 stores and dive times CSL 55 O 2 stores (ml O 2 kg -1 ) CSL NZSL ASL AuFS R 2 = AnFS Dive duration (minutes)

90 75 70 GaSL Total oxygen stores (ml O 2 kg -1 ) R 2 =0.463 Ant FS CaSL AusSL CaSL Mex-winter NZ SL CaSLMex_Summer Dive duration (minutes)

91 Most animals dive within their cadl 1.5 Antarctic fur seal Ratio of mean dive duration to cadl r 2 = Mean dive depth (meters)

92 Australian Sea Lion

93 Time (hours) Dive depth (meters) Australian Sea Lion A day in the life

94 7 Australian sea lions continuously exceed cadl 6 5 Dive duration (min) x cadl 1 0 Mean cadl (2.3 min) Dive depth (m)

95 Winter 1988 Time (hours:min) 12:00 12:06 12:12 12:18 12:24 12: Dive depth (meters)

96 Ratio of mean dive duration to cadl Diving & Physiology differs between behaviors Australian sea lion Hookers sea lion Antarctic fur seal Australian fur seal CA sea lion mesoplealgic CA sea lion epipelagic cadl Dive depth (meters)

97 Northern Elephant Seal

98 Tagging Beaked Whales

99 Dive Patterns Long Deep Foraging Dives Zc Ziphius cavirostris Shallow Recovery Dives Surface Time Md Mesoplodon densirostris

100

101 Mean Dive Duration (min) Allometry of Diving Dives >100m 20 Penguins, Pinnipeds, Odontocetes 15 Rorqual Whales 10 Humpback 5 Fin Blu e Body mass (log kg)

102 Number of dives N = 7 whales Blue Whale - Dive Duration 30 N = 7 whales Aerobic Dive Limit Minimum COT Standard MR Dive time (min)

103

104 Physiology Is Not Always Limiting Prey distribution Depth Abundance Energy content Habitat limitations Bathymetry Seasonal productivity