W5: Vertebrate Physiology (Torpor & Hibernation) [Dr. Matt] Flashcards
(98 cards)
1
Q
Endothermy attributes? (3)
A
- Energetically costly.
- Produces heat via metabolism.
- Typically homeothermic.
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).
3
Q
Categories of heterothermic responses/Facultative hypothermic responses? (3)
A
- Daily torpor.
- Hibernation.
- Shallow rest phase hypothermia.
4
Q
Daily torpor?
A
=
5
Q
Daily torpor attributes? (3)
A
- Duration is hours-days.
- Depth of hypothermia is pronounced.
- Daily response.
6
Q
Hibernation?
A
= prolonged hypothermic state.
7
Q
Hibernation attributes? (3)
A
- Duration is days-weeks.
- Depth of hypothermia is pronounced.
- Seasonal response (normally hibernate in winter).
8
Q
Why do animals that hibernate normally hibernate in winter?
A
It’s because during winter there is high energetic consumption.
9
Q
Shallow rest-phase hypothermia?
A
=
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).
11
Q
Torpor?
A
= a collective term that refers to both hibernation & daily torpor.
12
Q
Eg of Hibernation?
A
Short-beaked echidna.
13
Q
Eg of Daily torpor?
A
North African elephant shrew.
14
Q
Eg of Shallow rest-phase hypothermia?
A
Red-headed finches.
15
Q
Explain North African elephant shrew? (4)
A
- Lovegrove et al (2001).
- Entry phase.
- Maintenance phase.
- Rewarming/Arousal phase.
16
Q
Lovegrove et al (2001) in a nutshell? ()
A
17
Q
Entry phase?
A
= when organism starts to reduce Tb as they enter torpor.
17
Q
Maintenance phase attributes? (2)
A
- Regulation of low Tb when in torpor.
- Where most energy savings are used up.
18
Q
Rewarming/Arousal phase attributes? (2)
A
- When they return to normal Tb.
- Most energetically expensive phase because of spike in MR.
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.
20
Q
Nicol & Anderson et al (2008) in a nutshell?
A
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.
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.
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.
24
Why were torpor & hibernation believed to be plesiomorphic traits?
It's because it was more common in phylogenetically older mammals & birds.
25
What are plesiomorphic traits?
= traits that are primitive (organisms share a common ancestor) & have been retained over time.
26
What happened earlier in the evolutionary history of endothermy?
There were full abandonments where some organisms reduced their metabolic rates to ectothermic stages/ectothermic levels (kindly explain this further).
27
What happened earlier in the evolutionary history of endothermy? [kindly explained further]
It could mean that there was:
- Evolutionary plasticity.
- Adaptive strategies.
- Loss of endothermic traits.
- Phylogenetic complexity.
28
Explain Evolutionary plasticity?
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.
29
Explain Adaptive strategies?
Organisms had to adapt to environments that favoured ectothermic metabolic rates or body temperatures.
30
Explain Loss of endothermic traits?
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.
31
Explain Phylogenetic complexity?
Speaks to how different lineages might have evolved endothermy independently & lost it, causing them to develop different forms/other forms of thermoregulation.
32
Elaborate what happened with the development of higher levels of endothermy? (2)
- Now, you have partial abandonments, so some metabolic heat production.
- Maintain body temperature slightly above environmental temperature.
33
Explain the Lovegrove 2017 paper as it explains the origins of torpor & hibernation?
34
Recap: Introducing hibernation & torpor? (4)
- Categories of facultative hypothermic responses.
- Phases of torpor bouts.
- Examples of each category.
- Evolutionary origins of hibernation & torpor.
35
Phases of torpor? (4)
- Preparatory/Pre-hibernation.
- Entry phase.
- Maintenance phase.
- Rewarming phase.
36
Torpor Phase 1?
= involves phenotypic changes, fattening & diet.
37
Torpor Phase 2?
= involves the reduction of metabolic rates & body temperature.
38
Torpor Phase 3?
= involves body temperature setpoints & physiological aspects.
39
Torpor Phase 4?
= involves high energetic costs of internal heat productions.
40
Egs of how Torpor Phase 1 involves phenotypic changes? (2)
- Arctic ground squirrel.
- Siberian hamster.
41
Arctic ground squirrel attributes? (4)
- 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
Siberian hamster attributes? (3)
- 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
Torpor Phase 1: Pre-hibernation fattening attributes? (3)
- Hibernators gain up to 40% body mass.
- Mediated by various endocrine mechanisms.
- Dietary intake of polyunsaturated fats/polyunsaturated fatty acids is important.
44
What are the various endocrine mechanisms of pre-hibernation fattening mediated by? (2)
- Leptin regulates fat stores: stimulates satiety centre & suppresses appetite.
- A metabolic signal inhibited pre-hibernation.
45
How does polyunsaturated fatty acids (PUFAs) influence torpor patterns? (3)
- Maintains cell membrane function in torpor.
- Low body temperatures decrease lipid membrane fluidity.
- Increased intake of PUFAs increase membrane fluidity.
- Geiser & Kenagy, 1987.
46
Explain Geiser & Kenagy, 1987? ()
47
Eg of PUFAs intake?
Yelow pine chipmunk.
48
Torpor Phase 2 attributes? (3)
- Decrease in MR (<5% of normal).
- Decrease in Tb.
- Rate varies with body size.
49
Explain how Rate varies with body size? (2)
- Larger animals have lower SA:V ratios (shrew vs elephant).
- Thus, larger animals have a higher thermal inertia.
50
Thermal inertia?
= time taken for an animal to reach a new setpoint Tb through heat exchange with the environment across thermal gradients.
51
Eg of how rate varies with body size?
Combination of edible dormouse, golden mantled ground squirrel & alpine marmot.
52
Explain Combination of edible dormouse, golden mantled ground squirrel & alpine marmot? (3)
- 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
Torpor Phase 3 attributes? (4)
- 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
Physiological aspects of torpor? (6)
- 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
Attributes of the brain during torpor? (4)
- Overall reduced brain activity.
- Have exceptions in hypothalamus & brain stem pathways.
- Endogenous circadian/circannual clock.
- Yang et al, 2023.
56
Explain exceptions in hypothalamus & brain stem pathways? (3)
- Regulation of body & brain temperature.
- Regulation of cardio-respiratory function.
- Spontaneous & alarm signal driven arousals.
57
Explain Yang et al, 2023?
58
Torpor Phase 4?
= increasing metabolic heat production to reach normal Tb.
59
Torpor Phase 4 attributes? (4)
- 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
Eg of rewarming occurring through metabolic heat production?
Brazilian hummingbirds (Bech et al, 2006).
61
Summarise Bech et al, 2006 in relation to the rewarming phase?
- Use shivering to generate metabolic heat.
*Kindly add more points.
62
Eg of rewarming occurring through behavioural responses?
Fat-tailed False Antechinus (Geiser et al, 2002).
63
Summarise Geiser et al, 2002 in relation to the rewarming phase?
- Bask in the sun to decrease the need for metabolic heat production & saves energy.
*Kindly add more points.
64
Recap: Phases of torpor? (4)
- Preparatory/Pre-hibernation.
- Entry phase.
- Maintenance phase.
- Rewarming phase.
65
Ecology of the facultative hypothermic responses (heterothermic responses) in mammals? (3)
- Daily torpor = widespread.
- Hibernation = Widespread.
- Shallow rest phase hypothermia = Unknown.
66
Ecology of facultative hypothermic responses (heterothermic responses) in birds? (3)
- Daily torpor = Widespread.
- Hibernation = Very rare (1 known species).
- Shallow rest phase hypothermia = Widespread.
67
Ecological correlates of heterothermy? (3)
- Seasonal environments.
- Unpredictable environments.
- Unpredictable/seasonal food resources.
68
Egs of Seasonal environments? (2)
- Polar regions.
- Temperate regions.
69
Egs of Unpredictable environments? (2)
- El Nino zones.
- Deserts.
70
Egs of Unpredictable/seasonal food sources? (3)
- Nectar.
- Aerial insects.
- Fruit.
71
Ecological correlates?
= environmental factors that are associated with certain biological traits, behaviour, or patterns observed in animals.
72
Egs of ecological correlates in terms of Daily torpor? (2)
- North African elephant shrew.
- Freckled Nightjars.
73
Egs of ecological correlates in terms of Hibernation? (2)
- Arctic ground squirrel.
- Fat-tailed dwarf lemur.
74
Explain Ecological correlates: Daily torpor 1 - North African elephant shrew? ()
- Lovegrove et al. (2001).
-
75
Explain Ecological correlates: Daily torpor 2 - Freckled Nightjars? (6)
- 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
Explain Ecological correlates: Hibernation 1 - Arctic ground squirrel? (3)
- Barnes 1989.
- Hibernation to preserve energy in extreme cold.
- Limited to cold regions.
77
Explain Ecological correlates: Hibernation 2 - Fat-tailed dwarf lemur? (5)
- 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
Functions of torpor/hibernation? (7)
- 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
Main function of torpor/hiberantion?
To avoid energy mismatches in supply & demand.
80
Alternative functions of torpor/hibernation? (6)
- Fattening for migration.
- Optimising reproduction & development.
- Reducing parasite & disease load.
- Prolonging lifespan.
- Temporal partitioning of species.
- Water conservation (drought survival).
81
Eg of Fattenibg for migration as a function of torpor/hibernation?
Rufous hummingbirds.
82
Eg of Optimising reproduction & development as a function of torpor/hibernation?
Bats.
= Female bats store male sperms in winter & preserve them for a period when the environment has the most resources.
83
Aestivation in ectotherms attributes? (2)
- Dormant state (similar to hibernation in endotherms).
- Used for protection from environmental stressors (usually in summer).
84
Explain further on the dormant state observed in aestivation in ectotherms? (2)
- Inactive & lower MR.
- Tb depends on the Te.
85
What kinds of environmental stressors would cause ectotherms to go into aestivation? (2)
- Hot & dry conditions (droughts).
- Food shortages.
86
Aestivation?
= a state of dormancy that ectotherms enter into during very hot, dry or unfavourable conditions, especially during summer.
87
Egs of Aestivation? (2)
- African lung fish.
- Spade-foot frogs.
88
Explain African lung fish as an eg of Aestivation? (3)
- 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
Explain Spade-foot frogs as an eg of Aestivation? (3)
- Arid & semi-arid regions (extreme heat & droughts).
- Dig deep burrows to reach cooler, moister soil.
- Secretes mucous layer & reduces MR.
90
Recap: Ecological correlates of torpor? (5)
- Occurrence in mammals & birds.
- Examples of ecological drivers.
- Primary function: to avoid energy mismatches.
- Alternative functions of torpor.
- Aestivation in ectotherms.
91
Case studies on heterothermy? (2)
- Do African green-pigeons use torpor?
- Is torpor a water conservation strategy in Siberian hamsters?
92
Aim: Do Africa green-pigeons use torpor?
To investigate heterothermic responses of the African green pigeon in response to air temperature & food restriction.
93
Summary/Conclusion: Do Africa green-pigeons use torpor? (3)
- 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
Summary/Conclusion: Is torpor a water conservation strategy in Siberian hamsters? (3)
- Under acute food & food-and-water deprivation?
- Under acute water deprivation?
- Can water shortages induce torpor?
95
Under acute food & food-and-water deprivation?
Short day hamsters exhibited more frequent, shorter & shallower bouts, while long day hamsters exhibited no torpor.
96
Under acute water deprivation?
Short day hamsters exhibited more frequent, longer torpor bouts, while long day hamsters exhibited no torpor.
97
Can water shortages induce torpor?
Water shortages can regulate torpor patterns but food shortage is a stringer driver.
