Marine Mammal Respiration & Diving Physiology MARE 390 Dr. Turner

1. Marine Mammal Respiration & Diving Physiology MARE 390 Dr. Turner

2. Diving Most marine mammals spend a significant potion of their time underwater Foraging for food Increase swimming efficiency Reducing metabolic costs Minimizing risk of predation during sleep

3. Diving Capabilities Measured as maximum depth or duration Phocid N. elephant seal 1530(m) 77(min) S. elephant seal 1430(m) 120(min) Otariid Cal. sea lion 482(m) 15(min) Odobenid Walrus 300(m) 13(min)

4. Diving Capabilities Odontocete Sperm whale 3000(m) 138(min) Mysticete Fin whale 500(m) 30(min) Bowhead 352(m) 80(min) Sirenian W.I. manatee 600(m) 6(min) Dugong 400(m) 8(min) Sea otter 100(m)

5. Diving Capabilities

6. Diving Adaptations Cease breathing during diving events apneic conditions – conflicting conditions 1. O2 stores ↓ with ↑ activity (O2 demand) 2. CO2 & lactate ↑ in blood & muscle During hypoxic events, muscle activity is maintained anaerobically results in ↑ accumulation of lactate

7. Low-Impact Aerobics In the past 10-20 yrs – research emphasis on anaerobic dive physiology Recent on aerobic dive limits and how animals stay within these limits Know that aerobic diving is the only way to facilitate multiple sequential dives over a short period of time

8. Under Pressure Tolerate ↑ in water pressure 1 atmosphere (atm) for each 10m Sperm whale – 3000m (300atm) Squeezes air-filled spaces Absorbing gases at high pressure can be toxic – damage from bubbles Effect upon central nervous system

9. Out of Circulation Heart similar to other mammals – few adaptations Retia mirabilia – (wonderful net) tissue masses containing extensive spirals of blood vessels (mainly arteries) “red muscle”

10. Total Body Oxygen Stores Largest O2 stores in diving marine mammals Hemoglobin – O2 binding molecule of red blood cells; can deliver O2 where needed Myoglobin – O2 binding molecule of muscle cells; delivers O2 directly to muscles Hematocrit – packed red blood cell volume; hemoglobin volume – higher in mammals with increased diving capacity

11. Total Body Oxygen Stores Resp – Cardio – Cellular = All Equal Fewer mitochondria Cellular dominant More mitochondria

12. Total Body Oxygen Stores

13. Total Body Oxygen Stores

14. Total Body Oxygen Stores

15. Respiratory System Deep diving marine mammals have flexible chest walls – allow for collapse; lungs airless Trachea supported by cartilaginous rings maintains rigidity while alveoli collapse Lungs not larger than terrestrial mammals but important adaptations

16. Pinniped Lungs Multiple alveolar sacs in deep diving phocids Otariid Odobenid Phocid

17. Cetacean Lungs Cetacean lungs – greater elasticity Volume lower in deeper diving species Inability of respiratory tract to store gas WHY? Risks of embolism; bends Efficient air renewal - > 90% in single breath Sirenians – similar Humans – 10%

18. Total Body Oxygen Stores

19. Cetacean Lungs Oblique position – empties more completely efficient gas exchange Mysticete Odonticete

20. Da Bends! “Mini-Ditka, Tirty-tree, New York Giants, Twenty eight” – Bill Swerski Neither pinnipeds or cetaceans use lung volume to supply O2 during dive Pinnipeds – exhale before dive Cetaceans – inhale before dive Air pushed out of lungs at depth into trachea, bronchi Helps to stave off both bends (gas bubbles in blood) & nitrgogen narcosis (euphoria)

21. Dive Response During dive, available O2 ↓ (hypoxia) and CO2 ↑ (hypercapnia) Together create asphyxia Counteract with several adaptations: Anaerobic diving – no O2; lactic acid & H+ ions accumulate Bradycardia – decline in heart rate Ischemia – preferential distribution of blood to O2 sensitive organs; temperature & metabolic rate

22. Dugongs & Otters & Bears (Oh My!) Sirenians – long, extend posteriorly to kidneys - 2° buoyancy control Otters – 2.5 times terrestrial mammals; buoyancy control Polar Bear – little to no adaptations

23. Aerobic Dive Limit Longest dive that does not lead to an increase in blood lactate concentration If dive within ADL, can dive again immediately without recovery period If dive exceeds ADL and accumulate lactate; surface recovery period is required to “burn-off” (remove) lactic acid from the body

24. Aerobic Dive Limit ADL = Total O2 store (mLO2 ) / (Metabolic rate during dive (mL O2 x min-1) Total O2 store = O2 in blood, muscle, lungs ↑ ADL = longer and / or deeper the dive Foraging capacity related to the balance b/w total O2 store and metabolic rate

25. Aerobic Dive Limit

26. Aerobic Dive Limit

27. My Seal Is Broken! Phocids – correlation between body size & dive behavior (larger – longer) Hawaiian monk – typically shallow; deep diving recently identified (550m) Otariids – not as much time diving few minutes, shallow depths

28. Pinniped Diving Strategy 1. Apnea with exhalation (phocids) or inhalation (otariids) 2. Bradycardia 3. Peripheral vasoconstriction & hypoperfusion 4. Hypometabolism in ischemic tissues 5. Enhance O2 carrying capacity 6. Spleen for regulating hematocrit (large-phocids; typical - otariids)