W5: Vertebrate Physiology (Torpor & Hibernation) [Dr. Matt] Flashcards
Endothermy attributes? (3)
- Energetically costly.
- Produces heat via metabolism.
- Typically homeothermic.
Heterothermic endotherms attributes? (4)
- Some endotherms are heterotherms.
- Capable of facultative hypothermic responses (heterothermy).
- Reversible, controlled reductions in body temperature.
- Lower metabolic rates (conserve energy).
Categories of heterothermic responses/Facultative hypothermic responses? (3)
- Daily torpor.
- Hibernation.
- Shallow rest phase hypothermia.
Daily torpor?
=
Daily torpor attributes? (3)
- Duration is hours-days.
- Depth of hypothermia is pronounced.
- Daily response.
Hibernation?
= prolonged hypothermic state.
Hibernation attributes? (3)
- Duration is days-weeks.
- Depth of hypothermia is pronounced.
- Seasonal response (normally hibernate in winter).
Why do animals that hibernate normally hibernate in winter?
It’s because during winter there is high energetic consumption.
Shallow rest-phase hypothermia?
=
Shallow rest-phase hypothermia attributes? (2)
- Duration is hours to a single rest phase.
- Depth of hypothermia is shallow (<10 degrees celcius).
Torpor?
= a collective term that refers to both hibernation & daily torpor.
Eg of Hibernation?
Short-beaked echidna.
Eg of Daily torpor?
North African elephant shrew.
Eg of Shallow rest-phase hypothermia?
Red-headed finches.
Explain North African elephant shrew? (4)
- Lovegrove et al (2001).
- Entry phase.
- Maintenance phase.
- Rewarming/Arousal phase.
Lovegrove et al (2001) in a nutshell? ()
Entry phase?
= when organism starts to reduce Tb as they enter torpor.
Maintenance phase attributes? (2)
- Regulation of low Tb when in torpor.
- Where most energy savings are used up.
Rewarming/Arousal phase attributes? (2)
- When they return to normal Tb.
- Most energetically expensive phase because of spike in MR.
Explain Short-beaked echidna? (5)
- Nicol & Anderson, 2008.
- Burrow in soil.
- Multiple torpor bouts in hibernation.
- Torpor bouts last for weeks.
- All phases apply: entry, maintenance & rewarming/arousal phase.
Nicol & Anderson et al (2008) in a nutshell?
Explain Red-headed finches? (2)
- McKechnie & Lovegrove (2003).
- When animals were food-restricted they would decrease Tb & go into shallow rest-phase hypothermia.
Pros of Shallow rest phase hypothermia? (2)
- 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.
Evolutionary origins of torpor & hibernation? (3)
- 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.
Why were torpor & hibernation believed to be plesiomorphic traits?
It’s because it was more common in phylogenetically older mammals & birds.
What are plesiomorphic traits?
= traits that are primitive (organisms share a common ancestor) & have been retained over time.
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).
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.
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.
Explain Adaptive strategies?
Organisms had to adapt to environments that favoured ectothermic metabolic rates or body temperatures.
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.
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.
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.
Explain the Lovegrove 2017 paper as it explains the origins of torpor & hibernation?
Recap: Introducing hibernation & torpor? (4)
- Categories of facultative hypothermic responses.
- Phases of torpor bouts.
- Examples of each category.
- Evolutionary origins of hibernation & torpor.
Phases of torpor? (4)
- Preparatory/Pre-hibernation.
- Entry phase.
- Maintenance phase.
- Rewarming phase.
Torpor Phase 1?
= involves phenotypic changes, fattening & diet.
Torpor Phase 2?
= involves the reduction of metabolic rates & body temperature.
Torpor Phase 3?
= involves body temperature setpoints & physiological aspects.