Lecture 6

Question 1

Other vertebrates other than mammals have a much wider distribution of photoreceptor cells in their brains. Explain the difference and similarities of this

Answer 1

In mammals they are just confined to the retina but in other vertebrates they are distributed in cells around the brain which we call the brain photoreceptors.
However, the photopigments they use are very similar to rhodopsin in the retina

Question 2

Where is rhodopsin in the retina on mammals? Why is this important?

Answer 2

It is in the rod cells which is very important in peripheral vision

Question 3

What are the related family of photoreceptor proteins to rhodopsin? How do these proteins differ to rhodopsin?

Answer 3

Opsins but they are involved in deep brain photoreceptors and have different variants from the proteins in the retina

Question 4

What is absolute photorefractoriness?

Answer 4

When the sexual reproductive system is inhibited despite day length increasing

Question 5

Summarise the effects of photoperiod in timing of reproduction

Answer 5

. Increased day length imitates reproductive development in a photosensitive individual that has experienced short days
. Increases daylength sets off an endogenous inhibitory process- photorefractoriness- that eventually terminates reproduction
. The combined effect of photostimulation interacting with the endogenous inhibitory
Process sets up a window of time in which reproduction can occur during the annual cycle
. Fine-tuning of timing can occur within this window under the influence of supplementary cues
. State of photorefractoriness promotes the expression of the next annual cycle events (mould and autumn migration)

Question 6

Why does the reproductive system have to be switched off every year?

Answer 6

Because the reproductive hormones prevent the process of mould which changing their feathers is really in important to birds especially if they migrate but even if they don’t it is important for thermoregulation

Question 7

Explain the influence of rainfall on the breeding of Rufous-winged sparrow

Answer 7

They are photoperiodic but rainfall is required to enter full breeding conditions but the timing of rain is different from year to year.
The birds are able to tune in to when rainfall is highest and adjust their reproductive system so that it is fully active so that the environment is at its optimum for freshness their young.
(Is particularly important for species that are breeding in extreme environments such as deserts)

Question 8

In unpredictable environments animals must breed opportunistically whenever the environmental conditions are suitable. Give an example of an animal that shows this

Answer 8

Zebra finches in Australia

Question 9

Explain the breeding of the opportunistic breeder the red crossbill

Answer 9

. Breed in high northern latitudes (normally predictable)
. Eat coniferous seeds, feed their young on this, is found in autumn and winter
. Unpredictable food supply- patchy and irregular
. Highly nomadic, will range widely to find food
. Show particular cycles with a peak in the reproductive activity and a particular time of year in which moult occurs (late autumn)
. Indicates is a photoperiodic period window that is sensitive to changes in day length. They have a long breeding window (just like that of the quail) and there is less reproductive activity as that is switching off allowing them to moult

Question 10

What kind of bird are usually opportunistic breeders? Why is this?

Answer 10

Low latitude birds because conditions favouring breeding are often less predictable at lower latitudes and may extend for a longer period

Question 11

How does reproduction in birds living close to the equator differ to other regions?

Answer 11

Have very prolonged breeding seasons and produce their clutches over quite an extended period of time.
Whereas in northern latitudes it becomes much more concentrated due to the environmental conditions being unsuitable for breeding over a large part of the year (e.g. shown in starlings)

Question 12

What would you use to predict breeding of birds at high latitudes and birds living close to the equator?

Answer 12

High latitudes: rely more on day length to time their reproduction

Birds living close to the equator: are using local environmental cues for supplementary information

Question 13

How does the antbird differ and are similar to other equatorial birds?

Answer 13

. They are highly sensitive to photoperiod (unexpectedly), only need a change of 1 hour for the reproductive system to be stimulated so goes against expectation.
. Seems that because the change in day length is so small that actually seems to make them more sensitive
. Strong response to supplementary cues- insect food have a stimulatory effect on the reproductive system. So very sensitive to these supplementary local cues
. Tropical species may show relatively greater sensitivity to supplementary cues

Question 14

What percentage of oxygen consumption can be predicted by the heart rate in albatross?

Answer 14

91%

Question 15

How do you use the heart rate technique for predicted oxygen consumption in albatross?

Answer 15

Procedure: calibrations- have to check them over a lot of individuals in order to get some accuracy from your estimates, check them through validations and then monitor the heart rate while they are at sea. The implant can be implanted into the animal which is better for the animal compared to if it was outside it or it can be on the outside. Then measure for a long period of time- about a month

Question 16

What bird has the most efficient form of flight?

Answer 16

Albatross

Question 17

In birds what is the photoinducible phase?

Answer 17

The period when the reproductive system is most sensitive to light

Question 18

What is it that tells quails/ birds to develop the reproductive system?

Answer 18

It is the long lengths in spring that tell them to develop the reproductive system it is a proximate factor start and stops breeding season

Question 19

Where is photorefractoriness known to originate?

Answer 19

In the brain (but the mechanism is a mystery

Question 20

Give the example of how the experimenter that photoperiodic regulation underlies seasonal reproduction in opportunistic feeders and results

Answer 20

. Crossbills exposed to natural photoperiod in aviary
. Free access to food
. Underwent annual phase of gonadal regression and moult
. Photoperiodic control is more important than first thought
. Few records of clutches in wild populations during refractory period in autumn
. Relies more on supplementary cues than most other high latitude birds
. Supplementary cues remain to be identified

Question 21

Why is the crossbill an unusual opportunistic breeder?

Answer 21

Actually has a pattern more similar to what you would expect to see at the equator even though it is living in a highly predictable environment that has very cold winters

Question 22

What are the adaptions for tropical breeding in the spotted antbird?

Answer 22

. Equatorial forest in Panama 9^oN- low amplitude changes in daylength
. Seasonal nesting may-October
. Breed during rainy season (varies in onset between years)

Question 23

Give examples of British birds that are laying their eggs earlier

Answer 23

Corn bunting
Chiff-chaff
Magpie

Question 24

Some populations of birds benefit from breeding earlier and some don’t. What is the reason that some don’t?

Answer 24

Because some of the environmental sectors are becoming desynchronised

Question 25

Give an example of where climate change has caused desynchronisation

Answer 25

Dutch great tits:
. They still breed at the same time of year because when they breed is controlled by the daylength
. However, the insect larvae that they organise their breeding season around which is the time of year they can find the most caterpillars to feed their young on.
. Now the larvae/ caterpillar large numbers are occurring about two weeks earlier so they are now feeding their young at a sub optimal time

(Non-migrating species)

Question 26

What were the results of the experiment that was don’t with birds in semi-natural conditions where they were kept at 5 or 20 degrees and a control? (the experiment was ok starlings)

Answer 26

The birds that were kept at 5 degrees are identical to the birds at the natural temperature.
The ones at 20 degrees: at the start of the year it had no effect but the process of reproductive inhibition kicked in earlier, so they were doing the progression of moult earlier than the natural and 5 degrees group because of reproduction inhibition being earlier.
So the birds at warmer temps are a smaller window to breed

Question 27

When studying hormones in natural populations how do you do it using small blood samples; hormones measured by radioimmunoassay?

Answer 27

You raise an antibody to bind to a particular hormone that you want to measure and you’ve got a radioactive tag. Competes with unlabelled antibodies in the blood and they are competing for access to binding sites on an antibody and then look at the proportion that is labelled vs the proportion that isn’t and that can help you determine the concentration of a hormone in a tiny volume of blood extremely sensitively and can do it under field conditions without affecting their reproductive success

Question 28

What are the changes in emperor penguins during fasting?

Answer 28

. Behavioural index and display song 
. Corticosterone level 
. Uric acid level 
. Body mass loss 
. Plasma ‘beta sign’-OHB level

Question 29

How do the levels of the components that change during fasting in emperor penguins change?

Answer 29

. Corticosterone hormone starts going up
. Plasma beta-OHB, fat metabolism begins to decline
. The behavioural index and display song tends to go up towards the end (this is when the male is expecting the female to return)