Hill Ch 26 online: Diving Mammals Overview

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Questions and Answers

Dives by Weddell seals are mostly

  • long and shallow
  • short and shallow (correct)
  • short and deep
  • long and deep

Which animal is the deepest diver?

  • Fur seal
  • Weddell seal
  • Crabeater seal
  • Elephant seal (correct)

An animal's maximum possible blood store of O2 is calculated by

  • dividing the oxygen-carrying capacity of the blood by blood volume.
  • multiplying the oxygen-carrying capacity of the blood by blood volume and multiplying that product by animal mass
  • multiplying the oxygen-carrying capacity of the blood by blood volume. (correct)
  • multiplying the oxygen-carrying capacity of the blood by blood volume and then dividing by oxygen solubility

One of the most consistent features of diving species of mammals is that, relative to terrestrial species, they have

<p>very high myoglobin concentration in their skeletal muscle (A)</p> Signup and view all the answers

In diving mammals, the thorax

<p>is freely compressible during dives (D)</p> Signup and view all the answers

Which oxygen store (per kg) is significantly larger in true (phocid) seals, such as the Weddell seal, compared to a human?

<p>O2 bound to myoglobin and O2 bound to hemoglobin (A)</p> Signup and view all the answers

Which oxygen storage compartment tends to be the largest in diving mammals?

<p>Blood (B)</p> Signup and view all the answers

The predicted dive time of a Weddell seal based on calculations of its oxygen stores is likely to be

<p>shorter than (B)</p> Signup and view all the answers

Which statement regarding circulation and diving is false?

<p>During an episode of regional vasoconstriction, flow to parts of the brain is cut off or severely restricted. (A)</p> Signup and view all the answers

Because of a regional vasoconstriction during a prolonged dive, the heart responds with a reduction in

<p>cardiac output and heart rate (D)</p> Signup and view all the answers

In freely diving marine mammals, heart rate

<p>decreases in a graded manner with dive duration. (A)</p> Signup and view all the answers

Fish removed from water are likely to exhibit

<p>profound bradycardia (C)</p> Signup and view all the answers

During forced submergence, harbor seals deplete Oâ‚‚ in their ______ while Oâ‚‚ levels in their ______ remain high.

<p>muscles; blood (B)</p> Signup and view all the answers

Metabolic limits on dive duration are determined by all of the following except

<p>lactic acid clearance (D)</p> Signup and view all the answers

During a voluntary dive, a Weddell seal's metabolic rate is ______ that of a resting seal on land.

<p>lower than (A)</p> Signup and view all the answers

During a dive, blood pH tends to ______ due to an increase in ______ .

<p>decrease; COâ‚‚ and lactic acid (B)</p> Signup and view all the answers

The longest dive that can be undertaken without a net accumulation of lactic acid above resting level is called the

<p>aerobic dive limit (B)</p> Signup and view all the answers

What is the primary cause of decompression sickness?

<p>Formation of N2 bubbles in the blood (D)</p> Signup and view all the answers

The deepest dives of Weddell seals are at a depth of about _______ m.

<p>600 (B)</p> Signup and view all the answers

Following a 45-minute dive by a Weddell seal, circulating levels of lactic acid would likely fall to pre-dive levels after about ______.

<p>70 minutes (C)</p> Signup and view all the answers

Flashcards

Decompression sickness

A condition caused by nitrogen bubbles forming in the blood, often occurring when surfacing from a deep dive too quickly.

Weddell seal dives

Characterized by being mostly short and shallow.

Deepest Weddell seal dives

About 600 meters deep.

Elephant seal

The deepest diving mammal.

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Maximum blood oxygen stores

Calculated by multiplying blood oxygen capacity and blood volume.

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Diving mammal skeletal muscle

Has a very high concentration of myoglobin.

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Diving mammal thorax

Freely compressible during dives in some species.

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Sequestering O2 in lungs (diving)

Can prevent decompression sickness by slowing/stopping nitrogen diffusion, and provides a source of O2 during ascent.

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Aerobic dive limit

The longest dive possible without lactic acid buildup.

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Diving mammal circulation

Involves regional vasoconstriction to conserve oxygen during dives.

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Diving mammal heart rate

Decreases during prolonged dives..

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Fish removed from water

Will exhibit profound bradycardia (decrease in heart rate).

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Dive metabolism

During dives, blood O2 levels in muscles remain high as lungs deplete O2.

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Lactic acid recovery

After a 45-minute dive, circulating lactic acid levels take about 70 minutes to return to pre-dive levels.

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Metabolic dive limit

Depends on O2 stores, oxygen use rate, and lactic acid production.

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Dive-related blood pH

Blood pH decreases during a dive due to increased carbon dioxide and lactic acid.

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Study Notes

Diving Mammals and Conditions

  • Diving mammals avoid "the bends" by alveolar collapse, a crucial area for research.
  • Sequestering oxygen in lungs during deep dives has both advantages and disadvantages.
  • A disadvantage is oxygen not being available for the dive, however, the possibility of preventing decompression sickness due to slowing/stopping nitrogen during diffusion is a positive outcome. During ascent, alveoli opening allows resumption of diffusion for continued oxygen use.

Weddell Seal Diving

  • Weddell seals primarily conduct short, shallow dives.
  • Their deepest dives are approximately 600 m deep.

Deepest Diver

  • Weddell seals are the deepest divers among the listed animals (fur, elephant, crabeater seals).

Blood Oxygen Storage for Divers

  • Maximum blood oxygen storage is calculated by multiplying the oxygen-carrying capacity of the blood by blood volume.

Consistent Diving Mammal Feature

  • Diving mammals have high myoglobin concentrations in their skeletal muscle, contrasted with terrestrial species.

Diving Mammal Thorax

  • Diving mammals have a freely compressible thorax, which is in contrast to rigid thoraxes in other species and depths.
  • This is used in varying degrees dependent on the species.

Oxygen Stores in Diving Mammals

  • In true seals, O2 bound to myoglobin and hemoglobin is a larger oxygen store (per kilogram) compared to humans.

Largest Oxygen Storage Compartment

  • Lungs are typically the largest oxygen storage compartment in diving mammals.

Predicted Dive Times and Weddell Seals

  • Predicted dive times for Weddell seals using oxygen storage calculations tend to be shorter than actual maximal dives found in the wild.

Regional Vasoconstriction and Diving

  • Regional vasoconstriction during a prolonged dive reduces cardiac output and heart rate.
  • This is a critical part when considering circulatory adjustments during dives.

Freely Diving Marine Mammals

  • In freely diving marine mammals, the heart rate decreases in a graded manner with dive duration.

Fish Removed from Water

  • Fish removed from water typically exhibit profound bradycardia.

Harbor Seals During Forced Submergence

  • During forced submergence, harbor seals deplete oxygen in their muscles while blood oxygen levels remain high.

Weddell Seal Lactate Levels Post-Dive

  • Circulating lactate levels in Weddell seals fall to pre-dive levels approximately 70 minutes after a 45-minute dive.

Dive Duration Limits

  • Dive durations are restricted by oxygen stores, oxygen usage rates and lactic acid production.

Weddell Seal Metabolic Rate during Dive

  • Weddell seal's metabolic rate during voluntary dives is lower than a resting seal on land.

Blood pH During Dives

  • During dives, blood pH decreases due to increased carbon dioxide and lactic acid.

Aerobic Dive Limit

  • The longest dive without a net accumulation of lactic acid above resting level is the aerobic dive limit.

Primary Cause of Decompression Sickness

  • The primary cause of decompression sickness is the formation of nitrogen bubbles in the blood.

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