Acclimation to Constant Temperature
39
by the second batch of experimental animals was raised to 24 DC. Thus, animals acclimated for 3 days to constant temperature experienced a sudden
temperature rise or reduction of 13 DC. Relevant results are graphed in
Fig. 3.9. During the three first 3 days of the experiment, the respiratory behaviour of oribatids is similar to that recorded in the diplopod G. balcanica and
the collembolan o. meridiatus. Respiratory depression by the end of the
second day was about 30% and a further 10% respiratory decline was
recorded after 72 h.
All three oribatid species acclimated for 3 days to 11 DC responded rapidly
to rising temperatures (by 400% in the case of A. oudemansi). The effect of
falling temperature was not as pronounced as that of rising temperature, and
respiratory decline ranged from 30 to 60%. It is also worth noting that the
overall mean respiration metabolism in animals transferred from 11 to 24 DC
was higher than the one recorded in specimens acclimated for 3 days to this
temperature. Lowering temperature (from 24 to 11 DC) does not have an analogous effect.
From the above results it can readily be inferred that the response to
increasing temperature is a winter adaptation in most animals. At low winter
temperatures, arthropods exploit even the slightest temperature increases
and are able to accomplish energy-consuming activities such as egg synthesis
and deposition. In contrast, the broad optimal temperature range is an adaptation to hot weather. At the high temperatures that occur from late spring to
early autumn (when arthropods metamorphose into later developmental
stadia and deposit their eggs), metabolic activity is moderate (low QIO value)
and, as a result of energy compensation, remains more or less constant over
a broad temperature range. Thus, animals can avoid excessive increases in
their maintenance cost during the unfavourable period of drought.
To deal with temperature extremes, Mediterranean arthropods have developed respiratory strategies involving low metabolic rates, low QlOvalues and
broad temperature plateaux. Like scorpions from arid regions (Riddle 1978),
Mediterranean arthropods conserve metabolic reserves in response to variable temperature conditions. This results in minimising respiratory energy
loss. Furthermore, low respiratory QIO values result in metabolic homeostasis
following short-term temperature changes. Finally, broader temperature plateaux enable animals to optimise respiratory activity over larger temperature
ranges.
The respiratory physiology of Mediterranean arthropods may predictably
be modified by thermal acclimation. Hence, it is possible to simulate the
respiratory activity of animals under field conditions in order to elucidate
various aspects of their life history strategies in strongly fluctuating habitats.
Mediterranean arthropods respond rapidly to changing temperatures, irrespective of the conditions of acclimation, and have low maintenance costs at
low temperatures, while energy expenditure is comparatively low at higher
temperatures. Moreover, the capacity for energy transformation is distrib-
39
by the second batch of experimental animals was raised to 24 DC. Thus, animals acclimated for 3 days to constant temperature experienced a sudden
temperature rise or reduction of 13 DC. Relevant results are graphed in
Fig. 3.9. During the three first 3 days of the experiment, the respiratory behaviour of oribatids is similar to that recorded in the diplopod G. balcanica and
the collembolan o. meridiatus. Respiratory depression by the end of the
second day was about 30% and a further 10% respiratory decline was
recorded after 72 h.
All three oribatid species acclimated for 3 days to 11 DC responded rapidly
to rising temperatures (by 400% in the case of A. oudemansi). The effect of
falling temperature was not as pronounced as that of rising temperature, and
respiratory decline ranged from 30 to 60%. It is also worth noting that the
overall mean respiration metabolism in animals transferred from 11 to 24 DC
was higher than the one recorded in specimens acclimated for 3 days to this
temperature. Lowering temperature (from 24 to 11 DC) does not have an analogous effect.
From the above results it can readily be inferred that the response to
increasing temperature is a winter adaptation in most animals. At low winter
temperatures, arthropods exploit even the slightest temperature increases
and are able to accomplish energy-consuming activities such as egg synthesis
and deposition. In contrast, the broad optimal temperature range is an adaptation to hot weather. At the high temperatures that occur from late spring to
early autumn (when arthropods metamorphose into later developmental
stadia and deposit their eggs), metabolic activity is moderate (low QIO value)
and, as a result of energy compensation, remains more or less constant over
a broad temperature range. Thus, animals can avoid excessive increases in
their maintenance cost during the unfavourable period of drought.
To deal with temperature extremes, Mediterranean arthropods have developed respiratory strategies involving low metabolic rates, low QlOvalues and
broad temperature plateaux. Like scorpions from arid regions (Riddle 1978),
Mediterranean arthropods conserve metabolic reserves in response to variable temperature conditions. This results in minimising respiratory energy
loss. Furthermore, low respiratory QIO values result in metabolic homeostasis
following short-term temperature changes. Finally, broader temperature plateaux enable animals to optimise respiratory activity over larger temperature
ranges.
The respiratory physiology of Mediterranean arthropods may predictably
be modified by thermal acclimation. Hence, it is possible to simulate the
respiratory activity of animals under field conditions in order to elucidate
various aspects of their life history strategies in strongly fluctuating habitats.
Mediterranean arthropods respond rapidly to changing temperatures, irrespective of the conditions of acclimation, and have low maintenance costs at
low temperatures, while energy expenditure is comparatively low at higher
temperatures. Moreover, the capacity for energy transformation is distrib-