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BOMM > L14 - Sensory Systems of Marine Mammals > Flashcards

L14 - Sensory Systems of Marine Mammals Flashcards

1
Q

basics on sensory systems (3)

A
  1. comprised of sensory receptors, neural pathways, and parts of the brain
  2. receive and process information
  3. act as highly selective filters
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2
Q

umwelt

A

an organism’s self-centered world, or subjective universe

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3
Q

senses are essential to survival (7)

A
  1. orientation/navigation
  2. communication
  3. finding food
  4. detecting predators
  5. reproduction
  6. basis of decision-making: how to respond
  7. ultimately increases individual fitness
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4
Q

3 themes to consider

A
  1. terrestrial to aquatic or amphibious function
  2. relationship between the medium and the message
  3. science of sensory ecology
    - what info is obtains (the message)
    - how is it obtained (the mechanism)
    - why the information is useful (the function)
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5
Q

how to study sensory systems (7)

A
  1. observation and measurement
  2. field experiments/playbacks
  3. anatomical studies
  4. neurophysiological studies
  5. psychophysical studies - psychological perception of physical stimuli
  6. detection, discrimination, recognition
  7. senses studies individually but used in concert
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6
Q

marine mammal sensory systems (5)

A
  1. vision
  2. audition - passive hearing, biodolar
  3. mechanoreception - touch, hydrodynamic reception
  4. chemoreception - taste, smell?
  5. others?
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7
Q

vision: environmental constraints (5)

A
  1. rapid attenuation with depth
    - 65% of visible light absorbed ~1m
    - 99% of visible light absorbed by 100m
  2. blue light penetrates the deepest
  3. limited range due to particles and turbidity
  4. refractive properties different in water (focusing and acuity)
  5. very small amounts of biological light in deep water
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8
Q

visual adaptaions: light gathering (7)

A
  1. large eyes
  2. increased photoreceptor density
  3. increased % of rods, decreased % of cones
  4. increased pigments for blue light detection
  5. large dynamic pupillary range
  6. rapid dark-adaptaion rates
  7. well-developed tapetum lucidum
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9
Q

visual adaptations: pinnipeds

A

stenopaic (single slit) pupil

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10
Q

visual adaptations: odontocetes

A

double slit pupil, double fovea

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11
Q

visual adaptations: field of view (2)

A
  1. pinnipeds, otter, polar bears:
    - binocular vision
    - field decrease, depth perception increase
  2. cetaceans, sirenians
    - monocular vision
    - field increase, depth perception decrease
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12
Q

visual adaptations: acuity (5)

A
  1. spherical lenses in marine mammals to compensate for lack of refractive power in water
    - no bending of light at cornea in water
  2. special (accommodative) mechanisms in pinnipeds for vision in air
    - strong ciliary muscles to stretch lens
    - flattened cornea
    - “pinhole camera” effect in air
  3. sea otters can dramatically change the curvature of the lends by moving fluid to create pressure differentials
  4. rounded lens bends light in water but not in air
  5. thus, see otters have good acuity in both media
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13
Q

visual adaptations: adaptations to turbidity (2)

A
  1. reduces, poorly developed eyes

2. walrus, river dolphin, dugong

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14
Q

audition - passive hearing: environmental constraints (4)

A
  1. water denser than air - less attenuation, travels further
  2. speed of sound much faster in water than air (1500 m/s vs. 340 m/s)
  3. wavelengths of sound longer in water
  4. energy lost at fluid/air barriers - impedence mismatch
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15
Q

challenges of hearing in water (3)

A
  1. sound conduction
  2. sound localization
  3. hearing at depth (pressure)
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16
Q

challenges of hearing in water: in air (2)

A
  1. high impedence (density) mismatch

2. bone and tissue conduction is minimal

17
Q

challenges of hearing in water: underwater (2)

A
  1. low impedence mismatch

2. bone and tissue conduction is increased

18
Q

auditory anatomy (6)

A
  1. external ear reduced or absent
  2. ear closure mechanisms for some species
  3. very dense bones
  4. different sound conducting paths
  5. different structural morphology - frequency sensitivity, vascularized tissue, etc
  6. ear semi- or mostly-isolated from skull - to improve localization
19
Q

sound pathways for underwater hearing (3)

A
  1. more complicated, increased efficiency
  2. bone, tissue, and fat conduction involved
    - odontocetes: mandibular fat channels
    - sirenians: zygomatic fat channels
    - pinnipeds: multiple paths likely through the body
  3. sound waves travel to inner ear
    - energy conversion to neural impulses
    - role of basilar membrane
20
Q

ex: harbor seal (6)

A
  1. absent or reduced pinnae
  2. muscular control of external ear
  3. thickened, collapsible canal
  4. cavernous tissue
  5. dense auditory bulla
  6. enlarged middle ear ossicles
21
Q

basilar membrane morphology (2)

A
  1. in the cochlea of the inner ear

2. where sound energy is translated to neural impulses

22
Q

mechanireception (4)

A
  1. cetaceans: mainly the skin
    - whales: ~100 thin sensory hairs around jaws
    - solphins: 2-10 follicles around jaws
    - river dolphins: immobile thin bristles around jaws
  2. otters: sensitive front paws, vibrissae
  3. manatees: sensory hairs
    - all over body, high specialized around mouth
  4. pinnipeds: specialized vibrissae
23
Q

vibrissae (5)

A
  • different from terrestrial mammals
    1. enlarged
    2. stiffer
    3. greater blood flow
    4. denser innervation
24
Q

seal vibrissae (4)

A
  1. > 1000 nerves/follicle (humans 100 nerve/follicle)
  2. sensitive to size, shape, surface structure of objects
  3. detection of hydrodynamic motion
  4. largest portion of brain devoted to this sense
25
sirenians (5)
1. sensory hairs over body 2. facial sinus hairs 3. perorial "bristles" 4. highly movable 5. "prehensile" - can evert and grasp
26
chemoreceotion: olfaction | generally poorly studied) (4
1. cetaceans: nonfunctional? - odontocetes: olfactory bulb absent - mysticetes: olfactory bulb reduced or absent 2. manatees: poorly developed, rudimentary 3. pinnipeds: good function in air - more reduced in phocids than otariids or odobenids 4. otters and polar bears: well developed
27
harbor seals (3)
1. detect minute levels of DMS 2. DMs emitted by blooms 3. used to find fish?
28
chemoreception: gustation | generally not well developed anatomically, but poorly studied) (3
1. dissolved substances detected by taste buds 2. all marine mammals have taste buds - dolphins: sour, sweet, bitter, salty - sea lions: sour, bitter, salty (not sweet) - usually worse than humans 3. psychophysical and physiological methods
29
magnetoreception? (5)
1. response to geomagnetic field of the earth - magnetic fields same in air and water - magnetite found in cetacean skulls - limited correlational evidence - receptors, neural pathways unknown or nonexistent?

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