4/18/2012. Northern Fur Seal Three Foraging Patterns. Thermocline. Diving Physiology and Behavior

Transcription

1 Northern Fur Seal Three Foraging Patterns Thermocline Diving Physiology and Behavior 1

2 Fundamental Constraint on Foraging Behavior Return to Surface to Breathe 2

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

4 Marine Mammal Publications 50 No. of Publications Diving N = 381 Tracking N = Year Why Marine Mammals Dive? 1) To find food 2) To avoid predators 3) Energy efficient 4

5 Figure 1: 0 Sea otter Walrus Marine Mammal Diving Depths Otariids Phocids Odontocetes Mysticetes Dive depth (m) Average Depth Max Depth Figure 1: 0 Sea otter Walrus Marine Mammal Diving Depths Otariids Phocids Odontocetes Mysticetes Dive depth (m) Average Depth Max Depth 5

6 Figure 1: 0 Sea otter Walrus Marine Mammal Diving Depths Otariids Phocids Odontocetes Mysticetes Dive depth (m) Average Depth Max Depth Diving Physiology I. Pressure effects II. Pressure diseases III. Breath hold diving 6

7 Pressure Effects Hydrostatic pressure pressure at depth due to weight of water column Hydrostatic Pressure Depth (m) Pressure (Atms) Surface Harbor seals, CA sea lions Elephant seals Sperm whales, beaked whales 7

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 Boyle s Law P V 8

9 Change in Volume with Pressure 1/2 1/3 1/4 Lung Collapse Graded process m in all marine mammals 9

10 Lung collapse begins at alveoli and works up Trachea Bronchus Bronchioles Alveoli How Do Marine Mammals Deal With Lung Collapse? 1) Reinforced terminal airways & trachea - cartilage and muscle reinforcement 10

11 Phocid Otariid Odobenid 11

12 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 Diving Physiology I. Pressure effects II. Pressure diseases III. Breath hold diving 12

13 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 Gas exchange occurs at alveoli Trachea Bronchus Bronchioles Alveoli 13

14 Nitrogen Absorption 14

15 Dolphins trained to do repetitive dives Sampled blood Build up of N 2 occurred Pressure Diseases 3) Decompression sickness Increase solubility at depth Gasses saturated in tissues Form bubbles in tissue/joints on ascent 15

16 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 Pressure & Temperature 1) Pressure may change protein structure and function 2) Pressure may influence viscosity of cell membranes 3) Temperature may influence enzyme functions 16

17 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 Table 1 Shallow Divers Dive on inhalation Dive repetitively Decompression sickness Possible, Avoidance? Pressure Squeeze Eliminate air space Diving Physiology I. Pressure effects II. Pressure diseases III. Breath hold diving 17

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19 Figure 2: Marine Mammal Dive Duration 100 Average Maximum Dive duration (minutes) 10 1 Sea otter Sirenia Walrus Otariids Phocids Odontocetes Mysticetes Figure 2: Marine Mammal Dive Duration 100 Average Maximum Dive duration (minutes) 10 1 Sea otter Sirenia Walrus Otariids Phocids Odontocetes Mysticetes 19

20 Figure 2: Marine Mammal Dive Duration 100 Average Maximum Dive duration (minutes) 10 1 Sea otter Sirenia Walrus Otariids Phocids Odontocetes Mysticetes 20

21 Breath Hold Diving Storing oxygen on board Lungs Muscle Blood Reduce oxygen usage Aerobic vs. Anaerobic metabolism 21

22 Diving Physiology The Early Years Studies of forced submersion Ducks vs. chickens (1800 s) Early Studies Forced breath-hold experiments 22

23 Dive Response A dramatic set of physiological changes that occur upon submergence Master Switch of life 23

24 Dive Response Extreme bradycardia Few beats per min Cardiac Output by up 90% Dramatic peripheral vasoconstriction Flow to heart and vital organs Muscles, skin, and other organs reduced Hypometabolism (End of dive spike of lactic acid) Physiological Changes from Forced Dive 24

25 Physiological Changes from Forced Dive Is The Dive Response Real? Forced dives No control over duration Maximum response (Fear) Natural dives Animals control duration, effort, oxygen use Graded response 25

26 Breath Hold Diving Storing oxygen on board Lungs Muscle Blood Reduce oxygen usage Aerobic vs. Anaerobic metabolism Humans (20ml O 2 /kg) Lungs: 24% Blood: 57% Muscle: 15% Figure 3 26

27 Odontocetes (35ml O 2 /kg) Lungs: 22% Blood: 30% Muscle: 48% Figure 3 Otariids (40ml O 2 /kg) Lungs: 13% Blood: 54% Muscle: 33% Figure 3 27

28 Phocids (60ml O 2 /kg) Lungs: 7% Blood: 65% Muscle: 28% Figure 3 Increased O 2 Stores Lung O 2 stores Reduced in deep divers Important in shallow divers 28

29 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 Myoglobin in relation to dive times 29

30 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 Otariids Phocids Odontocetes 20 Blood volume (% body mass) Sea otter Walrus N. fur seal Calif. sea lion Australian sea lion N. Z. sea lion Harbor seal Ring seal Ribbon seal N. ele seal Weddell seal Bottlenose dolphin Killer whale P. white sided dolphin Belugha whale Dall's porpoise 30

31 Spleen contraction Increases circulating red blood cells (hematocrit) 31

32 Breath Hold Diving Storing oxygen on board Lungs Muscle Blood Reduce oxygen usage Aerobic vs. Anaerobic metabolism Decrease Metabolism 1) body size 32

33 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) Decrease Metabolism 1) body size 2) Swim efficiently, streamlining 33

34 Decrease Metabolism 1) body size 2) Swim efficiently, streamlining 3) Hypometabolism Vasoconstriction & redistribution of blood 50% of resting metabolism costs due to organs Redistribute Blood Flow 34

35 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 Bradycardia 35

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38 Breath Hold Diving Storing oxygen on board Lungs Muscle Blood Reduce oxygen usage Aerobic vs. Anaerobic metabolism Biochemical Pathway of Metabolism Aerobic - Oxygen present - Produces ATP Anaerobic - No oxygen - Produces only 2 ATP - Lactic acid produced Figure 4 38

39 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 ) Aerobic Dive Limit Phylogenetic differences: O 2 stores Diving Metabolic Rate Dive depths & durations 39

40 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) 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) 40

41 Weddell Seals on Fast Ice Repeated blood, heart-rate, & metabolism measurements 41

42 ADL 90-95% of all dives < 20 min 42

43 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 43

44 Decrease in Lactic Acid with Time at Surface 20 min aerobic dive with 2 minute surface interval

45 20 min aerobic dive with 2 minute surface interval min anaerobic dive with 100 minute surface interval Why Dive Anaerobically? Can reach deeper depths Untapped resources Larger prey More continuous time at depth More time for pursuit Handling time 45