Section III - Diving and More

How deep do sea otters typically dive?

180 feet

How deep do elephant seals typically dive?

1,300 feet

How deep do baleen whales typically dive?

300 feet

How deep do dolphins typically dive?

990 feet

How deep do Cuvier's beaked whales typically dive?

3,000 feet

What is a consequence of breath-holding when diving?

Asphyxia

What is asphyxia?

decrease in available oxygen and increase in carbon dioxide

What special adaptations do marine mammals have for diving?

1) Suspension of gas uptake

2) Increased oxygen carry capacity

3) Reduced active metabolism in non-vital functions

4) Low specific metabolic rate

What are two ways that marine mammals suspend gas uptake?

1) Alveolar collapse

2) Exhalation before diving

What do pre-dive exhalation and alveolar collapse prevent?

1) The bends

2) Nitrogen narcosis

3) Oxygen toxicity

How are marine mammals able to carry more oxygen?

1) Increase in blood volume

2) High levels of myoglobin

How do marine mammals reduce their active metabolism while diving?

1) Diving bradycardia

2) Selective ischemia

3) Hypometabolism

What are two examples of diving bradycardia?

1) Tursiops truncatus reduces heart rate from 100 bpm to 12 bpm

2) Phocid seals reduce heart rate from 100 bpm to 5 bpm

What is selective ischemia?

Reduction of blood to non-vital organs, skin, and muscles

What is an example of selective ischemia?

Weddell seals stop circulation through the kidneys

What is hypometabolism?

Reduction in overall metabolic rate

Why do marine mammals have low metabolic rates?

Large size; animals have lower specific oxygen consumption

How do marine mammals navigate long-term migration?

1) Magnetoreception

2) Celestial cues

3) Infrasound

What is magnetoreception?

Detection of magnetic field to perceive direction, altitude, and location

What is infrasound?

Low frequency sound waves going through the earth

What do marine mammals use for short-range migrations?

1) Echolocation

2) Leads or cracks in ice as a map

3) Imprinting

4) Internal compass

How do marine mammals use imprinting for navigation?

Remember where holes are and calculate when half of their oxygen is used up

What is osmolality?

Salt content

What makes marine mammal environment more challenging than terrestrial environment for salt balance?

Hyperosmotic (high salt) environment

How do marine mammals regulate salt balance?

1) Conserve freshwater

2) Avoid dehydration

How do marine mammals consume water?

1) Extraction from seawater

2) Preformed dietary sources

3) Metabolic oxidation of food

How does metabolic oxidation consume freshwater?

Carbohydrate breakdown produces H2O as a byproduct

How can marine mammals maintain salt balance?

1) Limit salt intake

2) Excrete salt direction

How do marine mammals excrete salt directly?

Nephron in kidneys filter blood and reabsorb salt and water

What is characteristic of urine in the loop of Henle?

Highly concentrated at a greater osmolarity than sea water

What is a reniculate kidney?

Multi-lobed organ found in Pinnipeds and Cetaceans due to their large body size and diving

How do marine mammals lose a significant amount of H2O?

Evaporation across respiratory surfaces

How does water content in warm air compare to cold air?

Cold (23°C) air holds about half as much water as warm (38°C) air

How can animals conserve water that would be lost to respiration?

Nasal cavity acts as a temporal counter-current heat exchanger that extracts heat on inhale so that a colder exhale carries less water out of the body

What is a cause of water loss that is unique to females?

Nursing requires large quantities of water for milk production

What is the benefit of having a high fat, low water content of milk in marine mammals?

Promotes rapid growth of young

How does milk content of marine mammals compare to terrestrial mammals?

1) Lower water content

2) High fat content

3) High protein content

4) No carbohydrates

What is the function of sensory systems?

1) Allow animals to receive and process information

How do marine mammal sensory systems compare to terrestrial mammals?

Act as highly sensitive filters

What do marine mammal sensory systems form?

Umwelt

What is Umwelt?

an animal's perceptually limited construct of the world around them

What part of the nervous system are sensory systems?

Peripheral senses (not part of central system)

What are the four essential elements of a sensory system?

1) Sensor

2) Filter

3) Transducer

4) Central processor

What is the function of a sensor in sensory systems?

Captures environmental signal (receptor)

What is the function of a filter in sensory systems?

Removes junk and passes signal

What is the function of a transducer in sensory systems?

Converts signals to electrical impulses (nerves)

What is the function of a central processor in sensory systems?

Receives signal and interprets it

What is the central processor for marine mammals?

Brain

What is audition?

Detection of propagation of mechanical disturbance through a medium

How is sound formed?

Acoustic waves in water and air, which are elastic mediums

What is hearing?

Conversion of sound energy by biomechanical transducers (middle and inner ear) into electrical signals (neural impulses) that provide acoustic data to the central processor (brain)

What is functional hearing?

Range of frequencies that a species can hear

What are the forms of functional hearing?

1) Sonic

2) Infrasonic

3) Ultrasonic

What does it mean for sound to be sonic?

Within the human range of hearing

What does it mean for sound to be infrasonic?

Low frequency (<20 Hz)

What does it mean for sound to be ultrasonic?

High frequency (>20 Hz)

What is the most important sense for marine mammals?

Hearing

How does sound compare in air vs. water?

1) Water travels much faster in water (4.5x)

2)

How is frequency calculated?

f = speed of sound / wavelength

What factors affect speed of sound?

1) Salinity (increase in salinity = increase in speed)

2) Temperature (decrease in temperature = decrease in speed)

3) Pressure (increase in depth = increase in speed)

Write separate flashcards for the relationship between each factor that affects speed of sound in water and the actual speed

What are the parts of the ear?

1) Outer ear

2) Middle ear

3) Inner ear

What are the parts of the outer ear?

1) Ear flange

2) Ear canal

What is the function of an ear flange?

Sound diffraction and sound localization

What is the function of an ear canal?

Conveys sound to the middle ear

What is the structure of the middle ear?

Air-filled, bony lever and membrane

What is the function of the middle ear?

1) Amplify and tune signal

2) Transforms acoustic sound to mechanical components

(T/F) The middle ear varies among species in terms of volume, stiffness, and mass

True

How does odontocetes compare to mysticetes? (Complete card later)

1) Odontocetes are ultrasonic species

2) Mysticetes are infrasonic species

What is the function of the inner ear?

Converts sound into electrical impulses

What are the parts of the inner ear?

1) Cochlea

2) Vestibular system

What is the function of the cochlea?

Hearing receptor

What are the parts of the cochlea?

1) Basilar membrane

2) Organ of Corti

What is the function of the vestibular system organs?

Orientation and balance

What are two types of special adaptations for marine mammal ears?

1) External ear adaptations

2) Middle ear adaptations

What are the external ear adaptations of marine mammal ears?

1) Closure

2) Wall thickening

3) Wax plugs

What are the middle ear adaptations of marine mammal ears?

1) Thick mucosa

2) Broad Eustachian tubes

What is important to know about marine mammal species and their ear adaptations?

Each group has its own adaptations for hearing capabilities and the level of adaptation to water (often based on how long each species spends on land vs. water)

What happens to light in water?

1) Absorbed

2) Refracted

3) Scattered

What factors determine what happens to light in water?

1) Wavelength of light

2) Concentration of chlorophyll

3) Concentration and type of DOM

Light intensity ________ (increases/decreases) exponentially as it passes through the water column

Decreases

Which color of light travels the furthest in water?

Blue

What does it mean to be crepuscular?

Active during dawn and dusk

What are the parts of marine mammal eyes?

1) Cornea

2) Lens

What is the function of the cornea?

Focusing power

How does being underwater affect corneal function?

Loss of focusing power because light does not refract under water

How does the marine mammal lens compare to ours?

Lens is much stronger but causes myopia when out of water

What is unique about the cetacean lens?

1) Spherical shape

2) No ciliary muscles

3) Pupillary contractions with horizontal slit

What is the benefit of cetaceans having a horizontal slit in their pupil?

Infinite depth of field

What is unique about the pinniped lens?

1) Intermediate shape

2) Ciliary muscles to distory a thick lens

What is unique about the polar bear lens?

1) See like terrestrial mammals

2) Little adaptation to see underwater

What is unique about the sea otter lens?

Change the radius of lens curvature to see well in both air and water

What is unique about the sirenian lens?

Poor vision

What is the function of a pigmented retina in marine mammal eyes?

1) Absorbs light

2) Helps adapt to dark and light

3) Photoreceptors

What are the two types of photoreceptors?

1) Rods

2) Cones

What is the function of rods?

Specialized for low light level (sensitivity detector)

What is the function of cones?

Specialized for high light (color) (contrast detector)

High density of receptors ________ (increases, decreases) sensitivity

Increases

1 multiple choice option

Why is chemoreception much more difficult in water than air?

Diffusion of chemicals is less efficient (1000 times slower) in water

What senses are affected by chemoreception efficiency?

Smell and taste