ABSTRACT
Phenotypic flexibility in basal metabolic rate (BMR) in response to short-term thermal
acclimation was assessed in the Laughing Dove (Streptopelia senegalensis), a common
resident bird species distributed throughout most of southern Africa. I hypothesised that
S. senegalensis would display flexibility in BMR over short time scales and that this
flexibility would be reversible. Additionally, I hypothesised BMR to be repeatable, and
that changes in BMR would be correlated with changes in organ mass. I tested these
hypotheses by measuring BMR in three groups of 10 birds before and after a short-term
(21 day) thermal acclimation period to one of three air temperatures (10o, 22o & 35oC).
After acclimation the three temperature groups were randomly divided and reverseacclimated
for another 21 days to one of the two thermal environments not yet
experienced. After this reverse-acclimation period BMR was measured again. The dry
masses of the stomach, kidney, heart, intestines, liver and pectoral muscles of acclimated
birds were used to determine possible mechanistic correlates of BMR adjustments.
Additionally, by monitoring BMR every 4-6 days during cold (10oC) and heat (35oC)
acclimation I was able to assess the temporal dynamics of adjustments in BMR in
response to short-term thermal acclimation.
BMR was both flexible and reversible in S. senegalensis as a consistent
relationship between BMR and acclimation air temperature was observed after
acclimation and reverse-acclimation. BMR increased with decreasing acclimation
temperature. Furthermore, a significant proportion (25%) of the observed variation in
BMR was repeatable in the 22oC group in spite of the change in BMR induced by thermal
acclimation. The mechanistic correlate of BMR adjustment in S. senegalensis appears to
be metabolic intensity and not organ size, as the only organ to show a significant increase
in size was the intestine of the acclimated 10oC group, which was significantly heavier
than the intestine of the 22oC group. BMR also decreases in response to the reduction of
flight and/or exercise. Since this reduction was not accompanied by a correlated change
in organ mass or body mass, the reduction in BMR as a response to captivity appears to
be linked to metabolic intensity of the organs and skeletal muscles.
In S. senegalensis adjustments in BMR occur during the first 30 days of captivity
and thermal acclimation. The response in BMR to acclimation temperature is clearly
evident as BMR of the heat-acclimated group was significantly lower than the coldacclimated
group after 21 days. During the response period, which lasts approximately
30 days, BMR adjusts as a mechanism to offset the costs of thermoregulation and
habituation to captivity while other metabolic parameters such as body mass, body
temperature, and minimum wet thermal conductance adjust to captivity and the thermal
environment. After 30 days BMR of the cold and heat-acclimated groups converge on
0.68W, indicating that once the associated metabolic parameters adjust and stabilize in
response to the thermal environment, BMR continues to adjust to captivity.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/4573 |
| Date | 07 March 2008 |
| Creators | Chetty, Kinesh |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | 42813 bytes, 397357 bytes, application/pdf, application/pdf, application/pdf, application/pdf |
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