Marine Mammal Respiration & Diving Physiology MARE 390 Dr. Turner

Marine Mammal Respiration & Diving

Physiology

MARE 390Dr. Turner

Diving

Most marine mammals spend a significant potion of their time underwater

Foraging for foodIncrease swimming efficiencyReducing metabolic costsMinimizing risk of predation during sleep

Diving Capabilities

Measured as maximum depth or durationPhocid 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)

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)

Diving Capabilities

Diving Capabilities

Diving Capabilities

Diving Adaptations

Cease breathing during diving events apneic conditions – conflicting conditions1. 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

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

Under Pressure

Tolerate ↑ in water pressure

1 atmosphere (atm) for each 10mSperm whale – 3000m (300atm)

Squeezes air-filled spaces

Absorbing gases at high pressure can be toxic – damage from bubbles

Effect upon central nervous system

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”

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

Total Body Oxygen StoresResp – Cardio – Cellular = All EqualFewer mitochondria

Cellular dominantMore mitochondria

Total Body Oxygen Stores

Total Body Oxygen Stores

Total Body Oxygen Stores

Total (L, M, B)

Respiratory System

Deep diving marine mammals have flexible chest walls – allow for collapse; lungs airless

Trachea supported by cartilaginous ringsmaintains rigidity while alveoli collapse

Lungs not larger than terrestrial mammals but important adaptations

Pinniped Lungs

Multiple alveolar sacs in deep diving phocids

Phocid Otariid Odobenid

Cetacean Lungs

Cetacean lungs – greater elasticity

Volume lower in deeper diving species

Inability of respiratory tract to store gasWHY?Risks of embolism; bends

Efficient air renewal - > 90% in single breathSirenians – similarHumans – 10%

Total Body Oxygen Stores

Cetacean Lungs

Oblique position – empties more completelyefficient gas exchange

MysticeteOdonticete

Da Bends!

Neither pinnipeds or cetaceans use lung volume to supply O2 during dive

Pinnipeds – exhale before dive

Cetaceans – inhale before diveAir pushed out of lungs at depth into

trachea, bronchi

Helps to stave off both bends (gas bubbles in blood) & nitrgogen narcosis (euphoria)

“Mini-Ditka, Tirty-tree, New York Giants, Twenty eight” – Bill Swerski

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

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

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

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 accumulateBradycardia – decline in heart rateIschemia – preferential distribution of blood to O2 sensitive organs;

temperature & metabolic rate

BradycardiaDecreased heart rate - modest (sirenians), moderate (cetaceans) extreme (phocids)

Measured in diving mammals, birds, and reptiles

Ringed Seal

IschemiaA decrease in the blood supply to a bodily organ, tissue, or part caused by constriction of blood vessels

Preferentially to “core” organs – Brain, heart

Away from skin, muscles, lungs

Aerobic Dive Limit

BrainAbdomenDorsal muscle

Declining metabolism during dive

Aerobic Dive LimitDuring a dive, lactic acid accumulates as a waste product in the muscles; depletes O2 stores from myoglobin due to ↓ pH

Aerobic Dive Limit

O2Lactate

Heart

Aerobic Dive LimitInformation from archival tag recorders greatly expanded information regarding ADL and dive routine

Aerobic Dive Limit

Aerobic Dive Limit

Aerobic Dive Limit

Aerobic Dive Limit

Aerobic Dive Limit

Aerobic Dive Limit

Aerobic Dive Limit

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 divingfew minutes,shallow depths

Pinniped Diving Strategy

1. Apnea with exhalation (phocids) or inhalation (otariids)2. Bradycardia3. Peripheral vasoconstriction & hypoperfusion4. Hypometabolism in ischemic tissues5. Enhance O2 carrying capacity6. Spleen for regulating hematocrit (large-phocids; typical - otariids)