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BIO3B: Physiology To Behaviour > W5: Vertebrate Physiology (Torpor & Hibernation) [Dr. Matt] > Flashcards

W5: Vertebrate Physiology (Torpor & Hibernation) [Dr. Matt] Flashcards

1
Q

Endothermy attributes? (3)

A
  • Energetically costly.
  • Produces heat via metabolism.
  • Typically homeothermic.
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2
Q

Heterothermic endotherms attributes? (4)

A
  • Some endotherms are heterotherms.
  • Capable of facultative hypothermic responses (heterothermy).
  • Reversible, controlled reductions in body temperature.
  • Lower metabolic rates (conserve energy).
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3
Q

Categories of heterothermic responses/Facultative hypothermic responses? (3)

A
  • Daily torpor.
  • Hibernation.
  • Shallow rest phase hypothermia.
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4
Q

Daily torpor?

A

=

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5
Q

Daily torpor attributes? (3)

A
  • Duration is hours-days.
  • Depth of hypothermia is pronounced.
  • Daily response.
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6
Q

Hibernation?

A

= prolonged hypothermic state.

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7
Q

Hibernation attributes? (3)

A
  • Duration is days-weeks.
  • Depth of hypothermia is pronounced.
  • Seasonal response (normally hibernate in winter).
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8
Q

Why do animals that hibernate normally hibernate in winter?

A

It’s because during winter there is high energetic consumption.

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9
Q

Shallow rest-phase hypothermia?

A

=

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10
Q

Shallow rest-phase hypothermia attributes? (2)

A
  • Duration is hours to a single rest phase.
  • Depth of hypothermia is shallow (<10 degrees celcius).
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11
Q

Torpor?

A

= a collective term that refers to both hibernation & daily torpor.

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12
Q

Eg of Hibernation?

A

Short-beaked echidna.

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13
Q

Eg of Daily torpor?

A

North African elephant shrew.

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14
Q

Eg of Shallow rest-phase hypothermia?

A

Red-headed finches.

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15
Q

Explain North African elephant shrew? (4)

A
  • Lovegrove et al (2001).
  • Entry phase.
  • Maintenance phase.
  • Rewarming/Arousal phase.
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16
Q

Lovegrove et al (2001) in a nutshell? ()

A
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17
Q

Entry phase?

A

= when organism starts to reduce Tb as they enter torpor.

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17
Q

Maintenance phase attributes? (2)

A
  • Regulation of low Tb when in torpor.
  • Where most energy savings are used up.
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18
Q

Rewarming/Arousal phase attributes? (2)

A
  • When they return to normal Tb.
  • Most energetically expensive phase because of spike in MR.
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19
Q

Explain Short-beaked echidna? (5)

A
  • Nicol & Anderson, 2008.
  • Burrow in soil.
  • Multiple torpor bouts in hibernation.
  • Torpor bouts last for weeks.
  • All phases apply: entry, maintenance & rewarming/arousal phase.
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20
Q

Nicol & Anderson et al (2008) in a nutshell?

A
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21
Q

Explain Red-headed finches? (2)

A
  • McKechnie & Lovegrove (2003).
  • When animals were food-restricted they would decrease Tb & go into shallow rest-phase hypothermia.
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22
Q

Pros of Shallow rest phase hypothermia? (2)

A
  • Organisms are not entering a lethargic state as hey are not reducing their Tb too much.
  • Organisms doing this won’t have a costly rewarming phase.
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23
Q

Evolutionary origins of torpor & hibernation? (3)

A
  • Believed to be an ancestral, plesiomorphic trait.
  • Earlier in the evolutionary history of endothermy.
  • As there was the development of high levels of endothermy, it became more difficult abandon.
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24
Q

Why were torpor & hibernation believed to be plesiomorphic traits?

A

It’s because it was more common in phylogenetically older mammals & birds.

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25
Q

What are plesiomorphic traits?

A

= traits that are primitive (organisms share a common ancestor) & have been retained over time.

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26
Q

What happened earlier in the evolutionary history of endothermy?

A

There were full abandonments where some organisms reduced their metabolic rates to ectothermic stages/ectothermic levels (kindly explain this further).

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27
Q

What happened earlier in the evolutionary history of endothermy? [kindly explained further]

A

It could mean that there was:

  • Evolutionary plasticity.
  • Adaptive strategies.
  • Loss of endothermic traits.
  • Phylogenetic complexity.
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28
Q

Explain Evolutionary plasticity?

A

This could be a result of the ecological niche that these organisms were in that led to some of these organisms reducing their metabolic rates to those of ectotherms.

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29
Q

Explain Adaptive strategies?

A

Organisms had to adapt to environments that favoured ectothermic metabolic rates or body temperatures.

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30
Q

Explain Loss of endothermic traits?

A

This speaks about how some lineages or species might have lost the endothermic traits over time possibly due to their environments which might have made endothermy less beneficial & more costly.

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31
Q

Explain Phylogenetic complexity?

A

Speaks to how different lineages might have evolved endothermy independently & lost it, causing them to develop different forms/other forms of thermoregulation.

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32
Q

Elaborate what happened with the development of higher levels of endothermy? (2)

A
  • Now, you have partial abandonments, so some metabolic heat production.
  • Maintain body temperature slightly above environmental temperature.
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33
Q

Explain the Lovegrove 2017 paper as it explains the origins of torpor & hibernation?

A
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34
Q

Recap: Introducing hibernation & torpor? (4)

A
  • Categories of facultative hypothermic responses.
  • Phases of torpor bouts.
  • Examples of each category.
  • Evolutionary origins of hibernation & torpor.
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35
Q

Phases of torpor? (4)

A
  • Preparatory/Pre-hibernation.
  • Entry phase.
  • Maintenance phase.
  • Rewarming phase.
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36
Q

Torpor Phase 1?

A

= involves phenotypic changes, fattening & diet.

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37
Q

Torpor Phase 2?

A

= involves the reduction of metabolic rates & body temperature.

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38
Q

Torpor Phase 3?

A

= involves body temperature setpoints & physiological aspects.

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39
Q

Torpor Phase 4?

A

= involves high energetic costs of internal heat productions.

40
Q

Egs of how Torpor Phase 1 involves phenotypic changes? (2)

A
  • Arctic ground squirrel.
  • Siberian hamster.
41
Q

Arctic ground squirrel attributes? (4)

A
  • Reflects seasonal up-regulation of specific genes & proteins.
  • Hibernate in cold soils.
  • Only organism to reduce Tb to <0 degrees.
  • Blood doesn’t freeze (form of supercooling).
42
Q

Siberian hamster attributes? (3)

A
  • Reflects seasonal up-regulation of specific genes & proteins.
  • When food is in short supply in winter, they undergo daily torpor.
  • Fur coats change from brown to white while in torpor (lethargic state).
43
Q

Torpor Phase 1: Pre-hibernation fattening attributes? (3)

A
  • Hibernators gain up to 40% body mass.
  • Mediated by various endocrine mechanisms.
  • Dietary intake of polyunsaturated fats/polyunsaturated fatty acids is important.
44
Q

What are the various endocrine mechanisms of pre-hibernation fattening mediated by? (2)

A
  • Leptin regulates fat stores: stimulates satiety centre & suppresses appetite.
  • A metabolic signal inhibited pre-hibernation.
45
Q

How does polyunsaturated fatty acids (PUFAs) influence torpor patterns? (3)

A
  • Maintains cell membrane function in torpor.
  • Low body temperatures decrease lipid membrane fluidity.
  • Increased intake of PUFAs increase membrane fluidity.
  • Geiser & Kenagy, 1987.
46
Q

Explain Geiser & Kenagy, 1987? ()

A
47
Q

Eg of PUFAs intake?

A

Yelow pine chipmunk.

48
Q

Torpor Phase 2 attributes? (3)

A
  • Decrease in MR (<5% of normal).
  • Decrease in Tb.
  • Rate varies with body size.
49
Q

Explain how Rate varies with body size? (2)

A
  • Larger animals have lower SA:V ratios (shrew vs elephant).
  • Thus, larger animals have a higher thermal inertia.
50
Q

Thermal inertia?

A

= time taken for an animal to reach a new setpoint Tb through heat exchange with the environment across thermal gradients.

51
Q

Eg of how rate varies with body size?

A

Combination of edible dormouse, golden mantled ground squirrel & alpine marmot.

52
Q

Explain Combination of edible dormouse, golden mantled ground squirrel & alpine marmot? (3)

A
  • Edible dormouse (90.2g), golden mantled ground squirrel (280g) & alpine marmot (3800g).
  • Differ in how long they take to enter the entry phase & drop Tb.
  • Larger animals will take longer to enter torpor & longer to rewarm (that’s why it’s mostly evident in smaller animals, as it is less beneficial to larger animals).
53
Q

Torpor Phase 3 attributes? (4)

A
  • Normothermy occurs.
  • During torpor set-point Tb & MR are reduced.
  • Set-point Tb is either above/at air temperature.
  • Won’t allow Tb to drop too below as it’s dangerous & they may destroy their bodily organ processes.
54
Q

Physiological aspects of torpor? (6)

A
  • Reduced Tb & MR.
  • Reduced heart rate.
  • Apneic breathing.
  • Some muscle atrophy.
  • Non-REM sleep (oleamide increases in brain).
  • Metabolic switch from carbohydrate to lipid catabolism.
55
Q

Attributes of the brain during torpor? (4)

A
  • Overall reduced brain activity.
  • Have exceptions in hypothalamus & brain stem pathways.
  • Endogenous circadian/circannual clock.
  • Yang et al, 2023.
56
Q

Explain exceptions in hypothalamus & brain stem pathways? (3)

A
  • Regulation of body & brain temperature.
  • Regulation of cardio-respiratory function.
  • Spontaneous & alarm signal driven arousals.
57
Q

Explain Yang et al, 2023?

A
58
Q

Torpor Phase 4?

A

= increasing metabolic heat production to reach normal Tb.

59
Q

Torpor Phase 4 attributes? (4)

A
  • Occurs through metabolic heat production or behavioural responses.
  • Organisms use different endogenous heat sources.
  • Mammals use shivering & non-shivering (BAT) thermogenesis.
  • Birds use shivering thermogenesis (primarily) & non-shivering thermogenesis (some).
60
Q

Eg of rewarming occurring through metabolic heat production?

A

Brazilian hummingbirds (Bech et al, 2006).

61
Q

Summarise Bech et al, 2006 in relation to the rewarming phase?

A
  • Use shivering to generate metabolic heat.

*Kindly add more points.

62
Q

Eg of rewarming occurring through behavioural responses?

A

Fat-tailed False Antechinus (Geiser et al, 2002).

63
Q

Summarise Geiser et al, 2002 in relation to the rewarming phase?

A
  • Bask in the sun to decrease the need for metabolic heat production & saves energy.

*Kindly add more points.

64
Q

Recap: Phases of torpor? (4)

A
  • Preparatory/Pre-hibernation.
  • Entry phase.
  • Maintenance phase.
  • Rewarming phase.
65
Q

Ecology of the facultative hypothermic responses (heterothermic responses) in mammals? (3)

A
  • Daily torpor = widespread.
  • Hibernation = Widespread.
  • Shallow rest phase hypothermia = Unknown.
66
Q

Ecology of facultative hypothermic responses (heterothermic responses) in birds? (3)

A
  • Daily torpor = Widespread.
  • Hibernation = Very rare (1 known species).
  • Shallow rest phase hypothermia = Widespread.
67
Q

Ecological correlates of heterothermy? (3)

A
  • Seasonal environments.
  • Unpredictable environments.
  • Unpredictable/seasonal food resources.
68
Q

Egs of Seasonal environments? (2)

A
  • Polar regions.
  • Temperate regions.
69
Q

Egs of Unpredictable environments? (2)

A
  • El Nino zones.
  • Deserts.
70
Q

Egs of Unpredictable/seasonal food sources? (3)

A
  • Nectar.
  • Aerial insects.
  • Fruit.
71
Q

Ecological correlates?

A

= environmental factors that are associated with certain biological traits, behaviour, or patterns observed in animals.

72
Q

Egs of ecological correlates in terms of Daily torpor? (2)

A
  • North African elephant shrew.
  • Freckled Nightjars.
73
Q

Egs of ecological correlates in terms of Hibernation? (2)

A
  • Arctic ground squirrel.
  • Fat-tailed dwarf lemur.
74
Q

Explain Ecological correlates: Daily torpor 1 - North African elephant shrew? ()

A
  • Lovegrove et al. (2001).

-

75
Q

Explain Ecological correlates: Daily torpor 2 - Freckled Nightjars? (6)

A
  • Smit et al. (2011).
  • Nocturnal.
  • Insectivores.
  • Activity related to luinar cycles.
  • During moon high = high Tb (suggests their hunting).
  • After moon high = decrease Tb & go into torpor.
76
Q

Explain Ecological correlates: Hibernation 1 - Arctic ground squirrel? (3)

A
  • Barnes 1989.
  • Hibernation to preserve energy in extreme cold.
  • Limited to cold regions.
77
Q

Explain Ecological correlates: Hibernation 2 - Fat-tailed dwarf lemur? (5)

A
  • Dausmann et al. (2005).
  • Not limited to cold environments.
  • Conserve energy when food supply is low.
  • Only occurs when food supply is low.
  • Don’t need to arise from torpor if Tb rises above 30C (if not, they will have to arise from torpor).
78
Q

Functions of torpor/hibernation? (7)

A
  • To avoid energy mismatches in supply & demand.
  • Fattening for migration.
  • Optimising reproduction & development.
  • Reducing parasite & disease load.
  • Prolonging lifespan.
  • Temporal partitioning of species.
  • Water conservation (drought survival?).
79
Q

Main function of torpor/hiberantion?

A

To avoid energy mismatches in supply & demand.

80
Q

Alternative functions of torpor/hibernation? (6)

A
  • Fattening for migration.
  • Optimising reproduction & development.
  • Reducing parasite & disease load.
  • Prolonging lifespan.
  • Temporal partitioning of species.
  • Water conservation (drought survival).
81
Q

Eg of Fattenibg for migration as a function of torpor/hibernation?

A

Rufous hummingbirds.

82
Q

Eg of Optimising reproduction & development as a function of torpor/hibernation?

A

Bats.

= Female bats store male sperms in winter & preserve them for a period when the environment has the most resources.

83
Q

Aestivation in ectotherms attributes? (2)

A
  • Dormant state (similar to hibernation in endotherms).
  • Used for protection from environmental stressors (usually in summer).
84
Q

Explain further on the dormant state observed in aestivation in ectotherms? (2)

A
  • Inactive & lower MR.
  • Tb depends on the Te.
85
Q

What kinds of environmental stressors would cause ectotherms to go into aestivation? (2)

A
  • Hot & dry conditions (droughts).
  • Food shortages.
86
Q

Aestivation?

A

= a state of dormancy that ectotherms enter into during very hot, dry or unfavourable conditions, especially during summer.

87
Q

Egs of Aestivation? (2)

A
  • African lung fish.
  • Spade-foot frogs.
88
Q

Explain African lung fish as an eg of Aestivation? (3)

A
  • Inhabit shallow waters that dry up during dry season.
  • Burrow into mud & form a mucous cocoon (4-6 months).
  • Reduce MR & breathe through lungs.
89
Q

Explain Spade-foot frogs as an eg of Aestivation? (3)

A
  • Arid & semi-arid regions (extreme heat & droughts).
  • Dig deep burrows to reach cooler, moister soil.
  • Secretes mucous layer & reduces MR.
90
Q

Recap: Ecological correlates of torpor? (5)

A
  • Occurrence in mammals & birds.
  • Examples of ecological drivers.
  • Primary function: to avoid energy mismatches.
  • Alternative functions of torpor.
  • Aestivation in ectotherms.
91
Q

Case studies on heterothermy? (2)

A
  • Do African green-pigeons use torpor?
  • Is torpor a water conservation strategy in Siberian hamsters?
92
Q

Aim: Do Africa green-pigeons use torpor?

A

To investigate heterothermic responses of the African green pigeon in response to air temperature & food restriction.

93
Q

Summary/Conclusion: Do Africa green-pigeons use torpor? (3)

A
  • African green pigeons use shallow rest phase hypothermia at low air temperature & when food restricted (similar to other columbids like Rock pigeons).
  • Cloven-feather doves use torpor under well-fed at <15C air temperature conditions.
  • No evidence of torpor in African green pigeons despite restricted feeding & exposure to 5C air temperature.
94
Q

Summary/Conclusion: Is torpor a water conservation strategy in Siberian hamsters? (3)

A
  • Under acute food & food-and-water deprivation?
  • Under acute water deprivation?
  • Can water shortages induce torpor?
95
Q

Under acute food & food-and-water deprivation?

A

Short day hamsters exhibited more frequent, shorter & shallower bouts, while long day hamsters exhibited no torpor.

96
Q

Under acute water deprivation?

A

Short day hamsters exhibited more frequent, longer torpor bouts, while long day hamsters exhibited no torpor.

97
Q

Can water shortages induce torpor?

A

Water shortages can regulate torpor patterns but food shortage is a stringer driver.

BIO3B: Physiology To Behaviour (15 decks)

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