Lecture 6 Flashcards
Other vertebrates other than mammals have a much wider distribution of photoreceptor cells in their brains. Explain the difference and similarities of this
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
Where is rhodopsin in the retina on mammals? Why is this important?
It is in the rod cells which is very important in peripheral vision
What are the related family of photoreceptor proteins to rhodopsin? How do these proteins differ to rhodopsin?
Opsins but they are involved in deep brain photoreceptors and have different variants from the proteins in the retina
What is absolute photorefractoriness?
When the sexual reproductive system is inhibited despite day length increasing
Summarise the effects of photoperiod in timing of reproduction
. 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)
Why does the reproductive system have to be switched off every year?
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
Explain the influence of rainfall on the breeding of Rufous-winged sparrow
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)
In unpredictable environments animals must breed opportunistically whenever the environmental conditions are suitable. Give an example of an animal that shows this
Zebra finches in Australia
Explain the breeding of the opportunistic breeder the red crossbill
. 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
What kind of bird are usually opportunistic breeders? Why is this?
Low latitude birds because conditions favouring breeding are often less predictable at lower latitudes and may extend for a longer period
How does reproduction in birds living close to the equator differ to other regions?
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)
What would you use to predict breeding of birds at high latitudes and birds living close to the equator?
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
How does the antbird differ and are similar to other equatorial birds?
. 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
What percentage of oxygen consumption can be predicted by the heart rate in albatross?
91%
How do you use the heart rate technique for predicted oxygen consumption in albatross?
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
What bird has the most efficient form of flight?
Albatross
In birds what is the photoinducible phase?
The period when the reproductive system is most sensitive to light
What is it that tells quails/ birds to develop the reproductive system?
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
Where is photorefractoriness known to originate?
In the brain (but the mechanism is a mystery
Give the example of how the experimenter that photoperiodic regulation underlies seasonal reproduction in opportunistic feeders and results
. 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
Why is the crossbill an unusual opportunistic breeder?
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
What are the adaptions for tropical breeding in the spotted antbird?
. Equatorial forest in Panama 9^oN- low amplitude changes in daylength
. Seasonal nesting may-October
. Breed during rainy season (varies in onset between years)
Give examples of British birds that are laying their eggs earlier
Corn bunting
Chiff-chaff
Magpie
Some populations of birds benefit from breeding earlier and some don’t. What is the reason that some don’t?
Because some of the environmental sectors are becoming desynchronised
