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Animal Ecophys Third Year > Lecture 8 > Flashcards

Lecture 8 Flashcards

1
Q

What are the short term/ acute effects of glucocorticoids (stress hormones in animals?

A

. Suppression of reproductive behaviour without affecting reproductive system
. Altered immune function
. Increased gluconeogenesis (mobilisation of energy stores)
. Increased foraging behaviour
. Promotion of escape (irruption behaviour during day
. Promotion of night restfulness

(Acute effects correspond to emergency life history stage)

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2
Q

What are the long-term effects of glucocorticoids (stress hormones) in animals?

A

. Inhibitstion of the reproductive system
. Immune suppression, impaired disease resistance
. Loss of protein from skeletal muscle
. Accelerated neuronal degeneration
. Suppression of growth

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3
Q

What happens if you administer corticosterone’s?

A

It can temporally stop reproductive behaviour although the reproduction may not change in size so the gonads will still be large but the birds won’t show any reproductive behaviour

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4
Q

By administering corticosterone’s it can temporally stop reproductive behaviour, but what else can it affect?

A

Can affect the immune function e.g. when there is something like a storm and birds have to adjust the way they eat/ get energy so if food is scarce they may need to increase foraging behaviour or it may be beneficial to get out of a particular area so might fly away even is your nest is in that area

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5
Q

How does the ‘capture, handling and restraint’ method to determine stress responsiveness in wild wilds work?

A

. Catch the bird. Take blood sample within 2 min of capture
. Bird subjected to standardised stressor
. Take blood at defined intervals (usually 5, 10, 30, 60 min) and measure the amount of corticosterone in the blood and over the hour you get a gradual increase

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6
Q

Why when using the ‘capture, handling and restraint’ method to determine stress responsiveness in wild birds do you take a blood sample within 2 min of capture?

A

Is a baseline before the bird has experienced the stressor

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7
Q

What is the standardised stressor that is used in the ‘capture, handling and restraint ‘ method to determine stress responsiveness in wild birds?

A

Being placed in a drawstring bag:
Place the bird in the bag for up to an hour. This is a physiological stressor maybe because it can’t move freely and is associated with being caught by a predator. It is not physically injured but it is enough of a stressor to activate the stress hormones

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8
Q

What is good about using the ‘capture, handling and restraint ‘ method to determine stress responsiveness in wild birds?

A

It is a highly reproducible technique applicable across different species, seasons and habitats

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9
Q

How can latitude affect stress response/ lower stress hormones?

A

Stress response can be reduced in high latitude breeding populations

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10
Q

Give an example of a higher latitude that shows reduced stress hormones in more northerly populations

A

Shorebirds that breed Alaska e.g: Semipalmated sandpiper

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11
Q

What is free (not total) corticosterone (stress responsiveness) related to?

A

The length of the breeding season

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12
Q

What are glucocorticoids?

A

Lipid soluble hormones

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13
Q

Since glucocorticoids are not proteins but lipid soluble hormones what is it hard for them to do?

A

To travel in the blood

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14
Q

The lipid soluble hormones, glucocorticoids, are not proteins therefore it is hard for them to travel in the blood. So what do they need to do?

A

So it is difficult for them to travel in the blood unless they are associated with a protein which makes them much more water soluble. So, to get around the body they need to associate themselves with proteins
(So protein circulating in the blood binds to glucocorticoids)

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15
Q

What are the proteins that glucocorticoids associate themselves with to get around the body called? Give an example of one

A

Binding globulins e.g. corticosteroid binding globulin (CBG)

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16
Q

What is the free hormone hypothesis?

A

That the hormone (glucocorticoids) travels associated with that a protein but becomes unbound from the hormone once it gets into cells and when it is exerting it’s biological actions it is in a free form as it is unbound from that binding protein
(So protein (binding globulins circulating in the blood is proposed to modulate access of glucocorticoids to tissues)

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17
Q

What is it that only the free hormone is believed to have?

A

The actual biological effects in the cells and is it is bound to the globulin then it is inactive

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18
Q

What is the standard way of measuring corticosterone?

A

By the process called radioimmunoassay

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19
Q

What does the process of of measuring corticosterone radioimmunoassay do?

A

Splits apart the hormone from its binding protein

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20
Q

Why do researches typically measure the total corticosterone?

A

They are not able to see bound from free glucocorticoids but you can do that but it takes longer but it is possible because if you take some measurements at the same time you can for any given blood sample work out how much binding protein is in there but most people don’t do it

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21
Q

Whether the hormone (glucocorticoids) is going to have biological effects can be regulated by what?

A

Regulated by whether it is bound to the binding protein or not

22
Q

Birds can regulate their response to corticosterone in fine detailed way. Give an example of this

A

For example they can regulate the amount of binding protein that they are producing

23
Q

How does birds regulating their amount of binding protein effect their response to corticosterone?

A

Because by regulating the amount of binding protein that they are producing can effect whether the corticosterone is going to have an effect on the biological effect in the tissues

24
Q

How can you measure corticosterone bound to CBG? Hence what can be estimated?

A

By measuring corticosterone concentrations, CBG binding capacity and affinity.
Hence can estimate ‘free’ corticosterone that exerts hormonal actions in tissues

25
Q

The does birds adjusting CBG concentrations provide the bird with?

A

A mechanism for fine-tuning its response to corticosterone (and therefore stressors)

26
Q

In what year was there extended snow cover, so extreme weather, in Alaska in spring?

A

2013

27
Q

The extended snow cover in Alaska 2013 meant it took birds longer to into their breeding grounds, how much did it delay their arrival by?

A

4-5 daysc

28
Q

What were the consequences of the delayed arrival of birds to their Alaska breeding grounds in 2013?

A

. Difficult to find food

. So faced energetic challenges when they arrived on the breeding grounds

29
Q

How did the extreme weather/ extended snow cover in Alaska 2013 effect longspurs and white crowned sparrows differently?

A

. They had less muscle and reduced fat stores in longspurs

. White-crowned sparrows had reduced muscle and increased fat

30
Q

How did the stress response (Corticosterone) in white-crowned sparrows and longspurs change in the 2013 extreme weather in their Alaska breeding grounds?

A

. The white-crowned sparrows showed no difference in stress response

. The stress response was increased in longspurs

31
Q

Why did longspurs stress response (Corticosterone) increase in the extreme weather in their Alaskan breeding grounds in 2013?

A

May have changed their strategy in response to reduced fat stores and muscle.
Prioritising survival over reproduction

32
Q

In the extreme weather in Alaska, 2013, both male and female longspurs had elevated levels of corticosterone which we would not expect from these birds breeding at higher latitudes. What would we expect? What does this indicate?

A

We would expect that they would switch off their areas response so this indicates that there is a trade off for each individual bird as it prioritises its survival over its reproductive success.

(So when the conditions are sort of ok they seem to prioritise their reproductive success but in these extreme conditions the longspur are choosing to prioritise it’s survival)

33
Q

Summarise what neuroendocrine adaptions to short Arctic summers include

A

. Weakened relationship between testosterone and aggression (so thy are not wasting time with territorial phase and get very quickly into the nesting cycle and to the point at which they are starting to feed young)
. Response to environmental stressors are modulated to allow nesting to proceed in adverse environmental conditions (saves time)
. (Note thee are separate adaptions, beware of confusing testosterone and corticosterone in exam answers)

34
Q

Lipids are lipophilic, what does this mean?

A

That you can store lots of carbon in them so you can store long carbon chains so you can store a lot of energy in a very small amount of space (so good for long distance journeys)

35
Q

Lipids aren’t soluble so what does this mean? Compare this to other fuel stores

A

That they have very little water associated with them compared to alternatives such as glycogen (a carbohydrate) or protein- so to store these you need a lot more water to accompany the energy source so lipids can store a lot of energy in a very small space (so good for long distance journeys)

36
Q

What do the level of premigratory fattening (migratory fat stores) depend on?

A

. How far they have to travel

. Whether they feed or not while they are travelling

37
Q

Explain premigratory fattening (fat stores) of the Gambel’s white crowned sparrow (how much they store, why this much)

A

Up to 30% body mass fast store because these will stop to feed because they are not actually travelling over water so they have the opportunity to stop and feed when they want

38
Q

It is birds that cross ecological barriers that show the most extreme changes. Give an example

A

The garden warbler which has to cross the Sahara desert and the Mediterranean so they can’t stop and feed

39
Q

What is the ‘record holder’ for migratory fat stores as % body mass?

A

Up to 50% in ruby-throated hummingbird- has to cross the Gulf of Mexico

40
Q

What are the other environmental cues other than long days that act to fine-tune migration timing?

A

Supplementary, modifying and synchronising information.
Local cues in the environment so food availability and temp and whether or not it is showing a stress response (these are all applying to migratory physiology just as they are to reproductive physiology)

41
Q

A body mass tracking system in the brain ensures what?

A

That the animal is at an appropriate mass for a given stage in its annual cycle

42
Q

What is basal corticosterone correlated with?

A

Migratory fat deposit so changes in body mass are very closely correlated to the levels of corticosterone

43
Q

What does the correlation between the levels of corticosterone and changes in body mass/ migratory fat deposition show?

A

That corticosterone doesn’t just come into play when animals are given a stressor it also has fundamental functions

44
Q

Because corticosterone doesn’t just come into play when animals are given a stressor but also has fundamental functions that what do the animals need? Why is this?

A

Need a minimum level to be able to feed properly and deposit fat

45
Q

Why is having a minimum level of corticosterone important?

A

Because it has important metabolic functions independent to its role to respond to stressors

46
Q

How did they experiment the effects of a Corticosterone receptor antagonist on migratory feeding? What were the results?

A

If you inject RU486 at the same time as corticosterone then it completely blocks the action of corticosterone in changing fat store. Use the drug in wintering birds and it didn’t have any effect on how much they were eating. They then looked at spring migratory birds and it decreased their weight so suggests corticosterone promotes appetite in the breeding season

47
Q

What happens if you inject RU486 at the same time as corticosterone?

A

It completely blocks the action of corticosterone in changing fat store

48
Q

What are the two effects of corticosterone?

A

. Basal (non-stressed) concentrations regulate food intake and fat deposition
. Stress-induced corticosterone secretion is associated with activating the emergency life history stage

49
Q

White collared sparrows in captivity were exposed to natural photoperiod, what effect did this have the body mass? Why did this happen?

A

That body mass increases in spring around April and some arrive at the breeding grounds around May. This body mass increase is due to body fat storage because they are becoming hungry at that time of year, so part of the brain is regulating appetite so fuel source

50
Q

Give the example of the a natural fasting animal; brooding hen (what makes her do it, how long for etc.)

A

The hen will sit on her eggs for about three weeks and her behaviour and physiology will change so that she can sit on her eggs for as long as she can do the internal tracking system in the brain switches down her appetite

Animal Ecophys Third Year (17 decks)

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