Adaptation of woodlice to temperature change.
ABSTRACT
The ability to acclimatise to different environmental changes varies from organism to organism and thus the need to determine the survival rate of the Metanoponorthus after a shift in temperatures they are accustomed to for their physiological functions. The experimental procedure was done to determine the survival rate of two Metanoponorthus (woodlice) samples pre-exposed to temperatures of 15oC and 25oC for two weeks and acutely exposed to 45oC until they appeared to have died. The 25oC woodlice generally showed a lower mortality rate compared to the 15oC ones at the acclimation period of 1.7min; 3.35min; 9.8min and 15.75min. This may have been attributed to the ability to acclimate to higher temperatures as they had already been exposed to such for the two weeks, giving rise to the warmer-is-better hypothesis. Genetic variation may also have played a role in the high mortality rate at 9.8min interval of the acclimation period of the 25oC woodlice which opposes the proposed hypothesis.
INTRODUCTION
An organisms’ ability to accustom to a changing environment has allowed the survival of species over years and the adaptation of the species to different environments, leading to not only phenotypic but also genetic changes. These have been able to ensure survival of an organism by changes in allele frequencies (Bradshaw, 1965; Pigliucci, 2001) that best suit the environment. Exposure to acute, short term disturbances however, in conditions suitable for survival would foster an organism to acclimatise to the changes in the environment so as to maintain or improve its behavioral as physiological functions and this is termed acclimation (Prosser, 1991; Cooper et al., 2010).
The plasticity (acclimation) can lead to improvements in energy absorption (Yamori et al., 2006), heat resistance or cold resistance, locomotion (Wilson & Franklin, 2000), tolerance of the environment (Dalghaard et al., 1998) as we all as success in mating (Wilson et al., 2007). Due to such benefits, the beneficial acclimation hypothesis was proposed, which predicted acclimation improved an organisms’ performance (Leroi et al., 1994; Huey & Berrigan, 1996) when changes in the environment are introduced, although this was not always the case. This is dependent on the stress an organism is exposed to as some organisms’ performance is enhanced whilst some is impaired and thus no resistance to the change (Karl et al., 2014).
In response to the beneficial acclimation hypothesis, the optimal- developmental temperature hypothesis (Huey & Berrigan, 1996), the warmer is better hypothesis as well as the colder is better hypothesis (Huey et al., 1999) which compared the survival of organisms after exposure to optimal, high as well as low temperatures during some stages of their development. These hypotheses tested the mortality rates of the adults after exposure to certain temperatures and their ability to acclimatise to various temperatures ensuring survival
The aim of this experimental procedure was to determine the survival of the woodlice at a very high temperature after pre-exposure to a low and a fairly high temperature in their developmental stages.
METHODS AND MATERIALS
As per practical schedule.
RESULTS
Results of this Practical lab have been removed. They are available in the original downloadable file. Search for it here.
DISCUSSION
The exposure to high temperatures in comparison to the other woodlice population has allowed the 25oC woodlice population to attain better acclimation to the 45oC temperature due to heat resistance as noted in the lower acclimation period at the start of the experiment. This attributing to a lower mortality rate compared to the 15oC and possibly supporting the Warmer-is-better hypothesis (Huey et al., 1999) hinting that such an exposure during development may have led to adults that outperformed those bred at a lower temperature. The general trend hence shows that as the acclimation period increased, the mortality rate decreased in the 25oC woodlice population (Cossins & Bowler, 1978).
Populations exposed to low temperature may acclimatize to lower temperature areas and may not survive high temperatures thus this may have explained the high mortality rates of the woodlice bred at 15oC
An increase in the mortality rate at 9.8min in the 25 woodlice population, may have been attributed to a variation in the genetic and phenotypic make-up of the woodlice. This was a sample of a population and variation in populations differ (Cooper et al., 2010), thus some may have been accustomed to a higher temperature, whilst some at that temperature would not have acclimatized and thus did not survive.
Generally both samples of the woodlice showed a low mortality as both populations recorded a number of survivors after the experiment, and this can be attributed to the physiology of the woodlice. They generally conserve a lot of water and at high temperatures the evaporation rate from their bodies decreases and thus ensures survival (Edney, 1952).
This concludes that organisms in a population would react differently to changes in the environment, leading to some attaining acclimation methods that enhance their performance in the existing environment whilst some would succumb to the acutely introduced stresses.
REFERENCES
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