The Porcellio scaber is most easily found in spring and autumn. Porcellio scaber Inhabit planted forests, urban areas and gardens. Found under organic material such as decomposing leaf litter and under bark or board in damp humid conditions. The Porcellio scaber are located in these areas due to proneness to desiccation. Porcellio scaber have a low surface area to volume ratio therefore are more likely to loose water rapidly through diffusion than other specie. The Porcellio scaber uses these damp and humid conditions to replace water diffusing rapidly out of their exoskeleton.
Reasons for the Porcellio scaber proneness to water loss is the result of a lack of a waxy, waterproof cuticle, which helps prevent water loss. This means the rate of water diffusion is much faster compared to other Athropods. The Porcellio scaber have adapted and formed techniques and physical features to help reduce water loss to prevent desiccation in the following waysâ€¦
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Clumping: This adaption was formed to reduce the surface
area to volume ratio of the Porcellio scaber this will reduce
water loss in less tolerable conditions.
Absorption: Porcellio scaber are able to reduce water loss by
transpirational losses, as they are able to take up water
through their uropods.
The behaviour of the Porcellio scaber helps to prevent excessive water loss e.g. Porcellio scaber congregate in cracks and crevices for protection from predators and to reduce water loss. This means Porcellio scaber can inhabit successfully in a range of terrestrial habitat.
Nutrition of a Porcellio scaber consists of plant and animal remains, rotting wood, soil, algae and fungi.
Reproduction of the Porcellio scaber occurs over summer months, October-March. "Day length and temperature are thought to be the reason for inducing seasonal reproduction."
The purpose of this investigation is to determine the average change in mass of groups of Porcillio scaber when placed in different water volumes in soil over a 48-hour period of time.
I believe as a result of this investigation I will find that Porcellio scaber in soil with the least amount of water will be the group of Porcellio scaber with the largest decrease in mass compared with Porcellio scaber located in soil with a larger water volume.
50x Porcellio scaber.
9x 10/5 cm containers
9x container lid
Soil (From habitat)
Measuring cylinder (ml)
1) Take 50 Porcellio scaber of the same size (1cm). Collected from their natural habitat, under leaf litter and decaying wood in damp cool humid conditions around 25 degrees.
2) Place Porcellio scaber in a 10/5 cm container consisting of their habitat soil. Make 10 holes in the lid to keep a constant airflow for the Porcellio scaber to keep the conditions and consisting elements as similar as possible to their natural environment.
3) Group Porcellio scaber in groups of five and weigh in their individual groups on a scale to determine the initial mass to use as a comparison further on in the experiment. Reasons for grouping Porcellio scaber in groups of 5 is because Porcellio scaber clump as natural protection. This is an adaptation that reduces surface area to volume ratio and will help reduce water loss. The groups will allow natural processors to take place as they would in the natural environment.
4) Fill one container with 2cm of soil (controlled variable), weigh this to find the initial mass to use as a control and establish the weights that will be used in the investigation. Desiccate this soil via oven then weigh again. Subtract final weight from the initial to find the difference. The difference will be used as the control. Find the three other water volumes by halving the control and adding half of it to the control its self e.g. (62.000 % 2=31.000 then 62.000+31.000=92.000). Repeat this to find the three water volumes that will be used in the investigation. Container 1 will be the control, this will be used to compare and contrast other water volume results. This container has 62.000ml of water.2nd container will be totally desiccated, 3rd will have water volume of 92.000ml. 4th will consist of 124.000ml of water and 5th 155.000ml.
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5) Add desiccated soil to 4 containers removing stick, rock and leaf litter. Compact soil with 5kg weight (Not forced just placed) to 2cm in height from the bottom of the container. Leave one container with soil that has not been manipulated for the Porcellio scaber habitat soil as a control to compare and contrast results against.
6) Add individual water volumes to 3 containers except for the desiccated soil and the control, as this does not require manipulation This will make the investigation more reliable as the amount of water will not be disturbed by water already present in the soil content .The independent variable is the water volume in each container of soil.
7) Place the groups of 5 Porcellio scaber in separate containers consisting of the 5 different water volumes.
8) Leave the Porcellio scaber for a 48-hour period of time in these different water volumes in a room consisting of a temperature around 25 degrees. This temperature is in the Porcellio scaber tolerance range that will not manipulate or alter their behavior as -0 degrees and below will slow enzymes in the Porcellio scaber cells and change their speed of movement or kill the Porcellio scaber as they can not tolerate sub zero conditions, which would alter the outcome of the investigation.
9) Remove all Porcellio scaber groups After the 48 hour period at the same time to keep time limit for each group the same (controlled variable). Which will result in a more accurate investigation.
10) Weigh each group of Porcellio scaber again to find the final mass after being exposed to the certain water volume. (Mass of Porcellio scaber is the dependent variable I am measuring in g).
11) Table results to establish the weight averages within the different water volumes in soil. Repeat investigation 3 times in order to get a reliable representative of the Porcellio scaber population.
The purpose of this investigation was to find out the average mass change of groups of Porcellio scaber in different water volumes in soil. In conclusion, the results from my investigation show that my hypothesis is correct. I found that the Porcellio scaber mass changed significantly in soil with different water volumes. The group of slaters exposed to the largest water volume 155.000ml in soil had an average of 0.103g which showed that this group of Porcellio scaber had the largest increase in mass compared to the average Porcellio scaber mass in the control soil 0.006g.The Porcellio scaber that were located in the desiccated soil had a decrease in mass 0.057g in comparison with the Porcellio scaber average mass in the control. A trend is apparent in the graph showing that when the Porcellio scaber is placed in greater water volumes in soil the mass of the Porcellio scaber increases.
This investigation was carried out to determine how change in water volume in soil affects the mass of the Porcellio scaber. In my investigation I found that Porcellio scaber in desiccated soil have a great decrease in mass 0.057g in comparison with the Porcellio scaber in the control soil with 62.000ml of water in soil 0.006 g this is a result of the Porcellio scaber being very sensitive and prone to water loss through the exoskeleton as the Porcellio scaber is densely covered in tubercles that release water.
This decrease in weight is used in contrast with the Porcellio scaber that were placed in the soil with the largest water volume in soil 155.000ml where the Porcellio scaber had a substantial increase in mass 0.103gCompared with the Porcellio scaber in the control soil which mass stayed the same throughout the investigation. Through observations I can see a trend where the Porcellio scaber increased in mass when exposed to larger water volumes in soil. This may be a resulting factor of the absence of the waxy, waterproof cuticle which other Athropods have which slows down the rate of diffusion so that water loss and gain is not so rapid and uncontrollable
Due to the Porcellio scaber proneness to desiccation, and this playing a big part in their behavioural activities, their adaptations are a biological success. Clumping and absorption of water through uropods are 2 of many ways the Porcellio scaber have formed abilities that compensate for their lack of a waxy, waterproof cuticle and rapid diffusion that this causes. Porcellio scaber can tolerate ranges of different habitats as these adaptations ensure protection to an extent.
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Through this investigation I have realised that Porcellio scaber exposed to increased and decreased water volumes show variation in mass change due to adaptations taking place to regain order in the Porcellio scaber.
Porcellio scaber are found in their favourable conditions which are damp and humid the Porcellio scaber in the soil with a greater water volume became very disorientated and did not move at same rate that Porcellio scaber in the controlled soil were this may be because the water volume was greater than their optimum tolerance range and they did not respond to over saturation in a positive way. Providing evidence that the Porcellio scaber cannot cope in those conditions for a long period of time.
Soil is a controlled variable, controlled by the amount of soil distributed in each individual container to keep the variable consistent. This is done using soil from the Porcellio scaber habitat, taken at the same time so that weather changes did not manipulate the water volume in the soil to ensure the reliability of the investigation. By removing stick, rock, leaf litter and excess water from the soil via oven, was a way of ensuring the substrate is of a consistent form (particles). This is done so when compacted with a 5 kg weight (placed not pressed) to compact the dirt, measuring from the bottom of the container to a 2cm height. this means the soil has the same density This allows the distribution of water to be consistent throughout the soil and to not be manipulated by other materials. This results in a more reliable investigation, as the soil consistency is an important factor when adding water. Porcellio scaber distribution is another important variable as it relates to the Porcellio scaber natural behaviour in a range of habitats. Porcellio scaber are regularly found in groups as an adaption to reduce water loss and for protection. In this investigation 5 Porcellio scaber have been used so that the clumping behaviour can take place. The reason for this is so the Porcellio scaber can perform similar behavioural activities as if they were in their natural habitat. This ensures a more valid investigation and better representation of the Porcellio scaber Porcellio population.
Volume of water added to each container measured in millilitres. This independent variable controls the results of the dependent variable. The variable is reliable because I have used the volume of water in the control 62.000 which I found out by measuring the original mass of the soil removed from the Porcellio scaber habitat then desiccating it via oven, and measuring again to find the final mass. I then subtracted this from the initial weight to find the difference, which resulted in being 62.000; this mass was then used as a control to establish the 3 other water volumes that were to be used in the investigation. Halving the control and adding the resulting number 31.000 to the control (62.000+31.000=92.000) and repeating this to each soil container needed by increasing the number by 31.000. The reason for halving the control is because I recognised that the Porcellio scaber cannot tolerate over saturation. To avoid harming the Porcellio scaber, I halved the control number and kept it in their tolerance range of damp conditions but slightly increased saturation level to show change. The dependent variable used in this investigation is mass of the Porcellio scaber measured in (g) the change in mass is being measured and the results were dependent on the volume of water that the Porcellio scaber were exposed to.
In the my initial method I was going to use 10 Porcellio scaber in each individual test, but this was changed, as I could not source enough Porcellio scaber for this to be possible. As a result I changed the quantity to 5, which was a good alternative as I found that in the Porcellio scaber natural environment they clump in smaller groups as a result of moist conditions, not having to use the clumping technique so intensely.