W11: Invertebrate Physiology (Insects & Thermal Physiology) [Dr. Blair]

Question 1

Insect attributes in terms of body temperature? (2)

Answer 1

• Ectotherms (“cold-blooded”).
• Poikilotherms.

Question 2

Poikilotherm?

Answer 2

= low physiological control of their heat balance.

Question 3

Temperature in this context?

Answer 3

= dictates insects’ survival, growth, digestion/metabolism, reproduction & distributions.

Question 4

Thermal basics for insects attributes? (5)

Answer 4

• Tolerance range.
• Development range.
• Optimal range (To).
• Critical thermal minimum (CTmin).
• Critical thermal maximum (CTmax).

Question 5

Tolerance range?

Answer 5

= temperature range within which an insect is able to survive.

Question 6

Tolerance range attributes? (2)

Answer 6

• Metabolic activity stops beyond this range.
• Insect becomes inactive beyond this range.

Question 7

Development range?

Answer 7

= temperature within which an insect’s physiological processes like development & growth can occur.

Question 8

Beyond the Development range?

Answer 8

Metabolic activity stops or slows down, halting development.

Question 9

Optimal range (To)?

Answer 9

= temperature range within which an insect’s physiological functions (metabolism, growth, reproduction and overall performance) are maximised.

Question 10

Optimal range (To) attributes? (2)

Answer 10

• Within this range, insects experience ideal conditions for survival & reproduction.
• Outside this range, physiological stress, reduced growth & survival risks can occur.

Question 11

CTmin?

Answer 11

= lowest temperature at which insects can survive before experiencing cold stress.

Question 12

CTmin attributes? (5)

Answer 12

• Metabolic activity stops.
• Loss of locomotion.
• Cold stress (chill coma).
• Hypothermia.
• No enzyme activity.

Question 13

If humans experience “cold stress” at ~20C, how long can insects go (CTmin)?

Answer 13

As low as -30C, which is seen in the Antarctic midge (the only insect in Antarctica).

Question 14

How is it possible for Antarctic midges to survive such low temperatures?

Answer 14

It is possible through supercooling.

Question 15

Supercooling?

Answer 15

= 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.

Question 16

CTmax?

Answer 16

= highest temperature at which insects can survive before experiencing heat stress.

Question 17

CTmax attributes? (5)

Answer 17

• Metabolic activity stops.
• Loss of locomotion.
• Heat stress (heat coma).
• Hyperthermia.
• Protein denaturation.

Question 18

Thing to note about mammals & CTmin?

Answer 18

Mammals don’t have a CTmin as they are endothermic.

Question 19

Name the critical thermal limits in insects. (2)

Answer 19

• CTmin.
• CTmax.

Question 20

Why do insects have critical thermal limits?

Answer 20

It’s because they are ectothermic.

Question 21

If humans experience “heat stress” at ~40C, how high can insects go (CTmax)?

Answer 21

As high as ~55C, as seen in Desert ants

Question 22

How are Desert ants able to survive under such high temperatures?

Answer 22

Heat shock proteins.

Question 23

Insects & Temperature: What does it encompass? (2)

Answer 23

• Cold stress (CTmin).
• Heat stress (CTmax).

Question 24

Insect physiological responses to cold stresses? (2)

Answer 24

• Cold hardening.
• Supercooling.

Question 25

Cold hardening attributes? (3)

Answer 25

- Releases cold shock proteins (CSPs) as you move into winter. - Bind onto protein to stabilise & prevent them from unraveling & breaking. - Depends on species & locality.

Question 26

What does cold hardening depend on as a tactic? (2)

Answer 26

- Species. - Locality.

Question 27

Is cold hardening enough when an insect is faced with freezing temperatures (<0C)?

Answer 27

No.

Question 28

What then if an insect is faced with freezing temperatures?

Answer 28

Supercooling.

Question 29

Supercooling attributes? (2)

Answer 29

- Uses cryoprotectants (sugars) that act as "antifreeze". - Prevents ice crystal formation in organs (no cell lysis).

Question 30

Insect physiological responses to heat stress/Heat waves/Summer?

Answer 30

Heat shock response.

Question 31

Heat shock response attributes? (3)

Answer 31

- Release heat shock proteins (HSPs) as you move into the summer. - Binds onto proteins to stabilise & protect the proteins. - Depends on species & locality.

Question 32

What do Heat shock responses depend on? (2)

Answer 32

- Species. - Locality.

Question 33

How do we discover the CTmin & CTmax of insects?

Answer 33

Through mimicking environmental conditions such as cold stress & heat stress by altering the water temperatures in water baths.

Question 34

CTmin, CTmax & Life stages?

Answer 34

Pupae & adult stages are the most resilient as they need to adapt to better reproduce & function through acclimating.

Question 35

Insects, Temperature & Climate Change attributes? (4)

Answer 35

- 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.

Question 36

Temperature implication: What is it most likely to affect? (3)

Answer 36

- Survival. - Reproduction. - Distributions.

Question 37

Categories/Types of insects? (3)

Answer 37

- Aquatic insects. - Terrestrial insects. - Fossorial insects.

Question 38

Which category of insects are buffered/protected/unaffected from elevated temperatures? (2)

Answer 38

- Aquatic insects. - Fossorial insects.

Question 39

Which category of insects is not buffered from elevated temperatures?

Answer 39

Terrestrial insects.

Question 40

Why are terrestrial insects impacted by elevated temperatures?

Answer 40

It's because they are thermally sensistive species.

Question 41

Impact of elevated temperature?

Answer 41

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.

Question 42

Eg of pest being problematic?

Answer 42

Cotton bollworm.

Question 43

Cotton bollworm?

Answer 43

= major generalist plant pest that causes significant damage to cotton & other crops.

Question 44

Why are Cotton bollworms problematic? (3)

Answer 44

- Crop damage. - Pesticide resistance. - Rapid reproduction & adaptability.

Question 45

Types of insects in terms of their distribution/range? (3)

Answer 45

- Winners. - Movers. - Losers.

Question 46

Winners attributes? (3)

Answer 46

- Generalists. - High thermal range. - Range expansion.

Question 47

Egs of Winners? (2)

Answer 47

- Invasive fruit flies. - Comma butterflies.

Question 48

Invasive fruit flies? (2)

Answer 48

- Benefit through being tropical species. - Loss of agriculture & biodiveristy.

Question 49

Comma butterflies? (2)

Answer 49

- Native to southern Europe. - Now throughout Europe due to milder winters.

Question 50

Movers/Shifters attributes? (3)

Answer 50

- Variety of generalists & specialists. - Variable thermal range (move with temperature). - Range shifts.

Question 51

Eg of Movers?

Answer 51

Mosquitoes.

Question 52

Mosquitoes? (2)

Answer 52

- Range increases or decreases depending on temperature. - Malaria vector.

Question 53

Losers attributes? (4)

Answer 53

- Specialists. - Low thermal range. - Range contraction. - Indirect effects.

Question 54

Egs of Losers? (2)

Answer 54

- Bumblebees. - Alpine insects.

Question 55

Bumblebees? (4)

Answer 55

- Increasing temperatures. - Overheating (Heat stress). - Heat waves in Europe. - Loss of pollination.

Question 56

Alpine insects? (3)

Answer 56

- Susceptible. - Solitary bee species. - Loss of pollination.

Question 57

What do the varying impacts of changing temperatures depend on? (3)

Answer 57

- Species. - Locality. - Ecological context.

Question 58

Super summary? (3)

Answer 58

- 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).