W11: Invertebrate Physiology (Insects & Thermal Physiology) [Dr. Blair] Flashcards
Insect attributes in terms of body temperature? (2)
- Ectotherms (“cold-blooded”).
- Poikilotherms.
Poikilotherm?
= low physiological control of their heat balance.
Temperature in this context?
= dictates insects’ survival, growth, digestion/metabolism, reproduction & distributions.
Thermal basics for insects attributes? (5)
- Tolerance range.
- Development range.
- Optimal range (To).
- Critical thermal minimum (CTmin).
- Critical thermal maximum (CTmax).
Tolerance range?
= temperature range within which an insect is able to survive.
Tolerance range attributes? (2)
- Metabolic activity stops beyond this range.
- Insect becomes inactive beyond this range.
Development range?
= temperature within which an insect’s physiological processes like development & growth can occur.
Beyond the Development range?
Metabolic activity stops or slows down, halting development.
Optimal range (To)?
= temperature range within which an insect’s physiological functions (metabolism, growth, reproduction and overall performance) are maximised.
Optimal range (To) attributes? (2)
- Within this range, insects experience ideal conditions for survival & reproduction.
- Outside this range, physiological stress, reduced growth & survival risks can occur.
CTmin?
= lowest temperature at which insects can survive before experiencing cold stress.
CTmin attributes? (5)
- Metabolic activity stops.
- Loss of locomotion.
- Cold stress (chill coma).
- Hypothermia.
- No enzyme activity.
If humans experience “cold stress” at ~20C, how long can insects go (CTmin)?
As low as -30C, which is seen in the Antarctic midge (the only insect in Antarctica).
How is it possible for Antarctic midges to survive such low temperatures?
It is possible through supercooling.
Supercooling?
= a physiological adaptation that allows insects to survive freezing temperatures by using cryoprotectants (“antifreeze”), which prevent the formation of ice crystals within their cells & tissues.
CTmax?
= highest temperature at which insects can survive before experiencing heat stress.
CTmax attributes? (5)
- Metabolic activity stops.
- Loss of locomotion.
- Heat stress (heat coma).
- Hyperthermia.
- Protein denaturation.
Thing to note about mammals & CTmin?
Mammals don’t have a CTmin as they are endothermic.
Name the critical thermal limits in insects. (2)
- CTmin.
- CTmax.
Why do insects have critical thermal limits?
It’s because they are ectothermic.
If humans experience “heat stress” at ~40C, how high can insects go (CTmax)?
As high as ~55C, as seen in Desert ants
How are Desert ants able to survive under such high temperatures?
Heat shock proteins.
Insects & Temperature: What does it encompass? (2)
- Cold stress (CTmin).
- Heat stress (CTmax).
Insect physiological responses to cold stresses? (2)
- Cold hardening.
- Supercooling.
Cold hardening attributes? (3)
- Releases cold shock proteins (CSPs) as you move into winter.
- Bind onto protein to stabilise & prevent them from unraveling & breaking.
- Depends on species & locality.
What does cold hardening depend on as a tactic? (2)
- Species.
- Locality.
Is cold hardening enough when an insect is faced with freezing temperatures (<0C)?
No.
What then if an insect is faced with freezing temperatures?
Supercooling.
Supercooling attributes? (2)
- Uses cryoprotectants (sugars) that act as “antifreeze”.
- Prevents ice crystal formation in organs (no cell lysis).
Insect physiological responses to heat stress/Heat waves/Summer?
Heat shock response.
Heat shock response attributes? (3)
- Release heat shock proteins (HSPs) as you move into the summer.
- Binds onto proteins to stabilise & protect the proteins.
- Depends on species & locality.
What do Heat shock responses depend on? (2)
- Species.
- Locality.
How do we discover the CTmin & CTmax of insects?
Through mimicking environmental conditions such as cold stress & heat stress by altering the water temperatures in water baths.
CTmin, CTmax & Life stages?
Pupae & adult stages are the most resilient as they need to adapt to better reproduce & function through acclimating.
Insects, Temperature & Climate Change attributes? (4)
- Temperature increases by 1-1.5C.
- Temperature increases unevenly globally (more at the equator).
- Bigger temperature increase as you move away from the Equator.
- Temperature fluctuations further from the Equator.
Temperature implication: What is it most likely to affect? (3)
- Survival.
- Reproduction.
- Distributions.
Categories/Types of insects? (3)
- Aquatic insects.
- Terrestrial insects.
- Fossorial insects.
Which category of insects are buffered/protected/unaffected from elevated temperatures? (2)
- Aquatic insects.
- Fossorial insects.
Which category of insects is not buffered from elevated temperatures?
Terrestrial insects.
Why are terrestrial insects impacted by elevated temperatures?
It’s because they are thermally sensistive species.
Impact of elevated temperature?
Elevated temperatures cause periods of drought, increased development, and increases in insect populations, which may make them problematic, as locust swarms are problematic to agriculture.
Eg of pest being problematic?
Cotton bollworm.
Cotton bollworm?
= major generalist plant pest that causes significant damage to cotton & other crops.
Why are Cotton bollworms problematic? (3)
- Crop damage.
- Pesticide resistance.
- Rapid reproduction & adaptability.
Types of insects in terms of their distribution/range? (3)
- Winners.
- Movers.
- Losers.
Winners attributes? (3)
- Generalists.
- High thermal range.
- Range expansion.
Egs of Winners? (2)
- Invasive fruit flies.
- Comma butterflies.
Invasive fruit flies? (2)
- Benefit through being tropical species.
- Loss of agriculture & biodiveristy.
Comma butterflies? (2)
- Native to southern Europe.
- Now throughout Europe due to milder winters.
Movers/Shifters attributes? (3)
- Variety of generalists & specialists.
- Variable thermal range (move with temperature).
- Range shifts.
Eg of Movers?
Mosquitoes.
Mosquitoes? (2)
- Range increases or decreases depending on temperature.
- Malaria vector.
Losers attributes? (4)
- Specialists.
- Low thermal range.
- Range contraction.
- Indirect effects.
Egs of Losers? (2)
- Bumblebees.
- Alpine insects.
Bumblebees? (4)
- Increasing temperatures.
- Overheating (Heat stress).
- Heat waves in Europe.
- Loss of pollination.
Alpine insects? (3)
- Susceptible.
- Solitary bee species.
- Loss of pollination.
What do the varying impacts of changing temperatures depend on? (3)
- Species.
- Locality.
- Ecological context.
Super summary? (3)
- The basics (poikilothermic, physiology linked to the ambient temperature).
- Thermal aspects (survival range, CTmin, CTmax, To, cold/heat stress proteins).
- Climate change (increasing/fluctuating temperatures, survival of groups/reproduction, distributions: winners, movers & losers).
