Effect of Humidness on Respiration Rate of Porcellio Scaber


Porcellio scaber are small, land dwelling crustaceans more commonly known as slaters or woodlice. They play an important role locally where they live as they feed on decaying matter such as lifeless leaves and rotting bark, allowing essential nutrition to re enter in the food string faster by depositing them in the soil through their faeces.

P. scaber are likely to prosper in a habitat that is damp and dark, and are therefore commonly found under bark, dropped logs and leaf litter, although in domesticated areas e. g. gardens, they can even be found underneath pots and firewood stacks. Apart from their solid exoskeleton, which forms armoured plates on their backs, P. scaber has little in the way of defence against predators. Thus they display photo kinesis, an orientation response where the stimulus, light, causes the slater to get started working in a arbitrary pattern, ceasing only when it offers found a place that is dark. Kinesis is a response where the stimulus determines the pace of movement, but not the way thus the slater will continue making random changes as it runs, to raise the potential for finding a far more appropriate environment. In this manner P. scaber is modified to avoid predators, as when it's in a dark place, including the underside of a log, it can't be seen by parrots or small mammals, which is therefore safer than if it was subjected. Because of its desire for low light levels P. scaber is most lively during the night, when parrots and a great many other predators are inactive, increasing its chances of survival.

P. scaber has also developed a second orientation response, hygro kinesis. With this version P. scaber is better in a position to find an environment with a favourable wetness. This is important as P. scaber, like most slaters, respires through "gills", more accurately called pseudo tracheae, which need a certain level of wetness for respiration to occur; otherwise the individual dangers desiccation, and resultantly death. Slaters tend to lose moisture very quickly through their cuticle and their pseudotrachea, and as such depend even more highly on the moisture of these environment to keep them wet than other varieties better designed to dry environments. Due to the hygro kinesis it is expected that P. scaber will have a higher activity rate in areas with lower % humidness, because they are moving to find more favourable conditions, and therefore the respiration rate of individuals in these drier conditions is higher in comparison to those in damper conditions. This is because mobile respiration is the method whereby energy is produced for functions within the cells, and thus an elevated activity rate will demand more energy and bring about a greater respiration rate, as the average person needs more air for cellular respiration that occurs.

  • Aim: To determine the aftereffect of different % dampness on the respiration rate of Porcellio scaber.
  • Hypothesis: Because of the positive hygro kinesis of Porcellio scaber, the bigger the % humidness, the lower the respiration rate of the individual.
  • Null Hypothesis: The % humidity of the environment will not have an effect on the respiration rate of Porcellio scaber.


Take the boiling pipe and add 1ml of magnesium chloride in the bottom. Ensure no magnesium chloride details the attributes of the boiling tube as this might poison or otherwise have an impact on the Porcellio scaber in the test. The magnesium chloride will create a 33% moisture above its surface, thus when the boiling tube is stoppered a uniform % wetness will be created.

Place enough gauze in underneath of the boiling tube that the magnesium chloride is clogged in the bottom. This also helps prevent the Porcellio scaber in the experiment from being poisoned. It is helpful to leave a tail of gauze up to the mouth of the boiling tube to make it much easier to remove and present the slaters something to climb over and cover beneath.

Take 0. 2g of soda pop lime and cover it in gauze. This ensures the slaters will not come into contact with the soda pop lime, however the wrapping is permeable enough to allow gases to go into the packet. The soda lime will absorb the skin tightening and made by the respiration of the slaters, making certain the change in level of air is representative of the oxygen used in respiration.

Place 4 adult Porcellio scaber in the boiling pipe. These have to be of an identical size so that their respiration rates are similar.

Place the bung with a gap in the centre into the mouth of the boiling tube tightly so that there surely is no chance of water leaking in to the boiling tube and drowning the slaters. Thread a graduated pipette into the opening. This creates an enclosed environment, stopping the slaters from escaping and ensuring the % wetness is retained constant. The pipette is maintained stable by the bung, protecting against fluctuations in the quantity of water in the pipette.

Place the boiling pipe sideways in a bathtub of water, ensuring the tip of the pipette is totally submerged. As the oxygen in the boiling tube is utilized by the slaters for respiration, and the carbon dioxide produced is assimilated by the soda lime, the volume of normal water in the pipette will increase as the volume of air lowers, allowing a big change in size to be determined.

Record the original volume of water in the pipette. This is most easily attained by measuring the amount of water in centimetres, and then switching the measurement into millilitres.

Cover the experiment so that the level of light is 0. 17 lux or less. This ensures that the experience of the slaters that will determine the pace of respiration will be scheduled only to their hygro kinesis, not both hygro and image kinesis mixed.

Leave the test for 7 time to allow plenty of time for the volume of normal water in the pipette to improve because of the respiration of P. scaber.

Record the new level of normal water in the pipette. As the in the pipette is replacing the air, we can conclude that the quantity of normal water is also the quantity of oxygen used in the respiration of P. scaber. Place ends in a stand and calculate the change in size, and so the respiration rate using the next formulas

To find the volume of drinking water: (cm·1. 8)x0. 1

As 1. 8cm is add up to 0. 1mL, in the graduated pipettes used in this test.

To find the respiration rate: (change in volume of test- change in level of control) · 28

As the control can be an experiment without P. scaber in it to provide the value of water moving into the pipette without respiration. Dividing by 7 and 4, for the amount of time and slaters to give the respiration rate in mL each hour for 1 slater.

Repeat steps 1-10 double more with magnesium chloride, and then once more omitting step 4 4, so that we now have 3 experiment established ups with slaters and 1 control without slaters.

Repeat steps 1-11, changing the magnesium chloride for magnesium nitrate (52. 9% moisture), sodium chloride (76% dampness), potassium chloride (85% moisture), and potassium nitrate (93. 5% wetness).

Repeat steps 1-12 at least 3 times to create a fair test environment, meaning the test size is large enough to be always a reasonable representation of the populace included, and enough results can be acquired to provide accurate conclusions.

Conclusion: In the results it can be concluded that as the % humidity raises, the respiration rate of P. scaber decreases. For example the highest humidity, 93. 5% produced the average respiration rate of 0. 003017 mL per hour, while the most affordable wetness, 33%, produced an average respiration rate of 0. 007804mL per hour, which is considerably greater. Thus we can see that the respiration rate of P. scaber is afflicted by the % humidness of its habitat.

Discussion: Porcellio scaber is a kinds that is extremely well adapted to residing in dark and wet environments, where other organisms may battle to survive. Due to these adaptations, its ecological niche market is very specific, and thus slaters are suffering from orientation replies (picture and hygro kinesis) that allow them to identify when the habitat is becoming significantly less than ideal and discover a new environment more suited to them. However as kineses are non directional reactions, the slater will continue to run until it has found a far more favourable environment. It had been this behavior that was the foundation for my experiment.

In pets, energy is produced by cellular respiration, an activity where by ATP (adenosine triphosphate), the widespread energy carrier in skin cells, is "charged" by breaking down chemicals such as proteins, lipids and sugars from food. The is then released by breaking one of the bonds within the ATP molecule, building ADP (adenosine diphosphate), and providing the power required for all functions in the skin cells. For mobile respiration to occur however, a gas exchange system is necessary, as aerobic respiration needs air that occurs and releases carbon dioxide. In Porcellio scaber this respiratory structure takes the proper execution of pseudotrachea, which are "Respiratory framework developed in pleopods of some Isopoda for air- breathing; they contain small ramified tubules inside limb starting outward in slit like apertures and filled up with air"1. Gas exchange occurs when air steps through the pseudotrachea through something of ever before smaller tubules that end either adjacent or near to each cell in the body. The ends of these tubules are filled with fluid. This liquid moistens the semi permeable cell membrane, allowing the diffusion of oxygen in to the cell from the area of high attentiveness in the tubules to the area of low amount in the cells. It also allows the throw away product of respiration, carbon dioxide, to diffuse out of the cell into the tubules and move out of the pseudotrachea. Because slaters are unable to close off their respiratory constructions as they are formed from a hard product called chitin, it is very easy for them to lose drinking water during respiration, and if there is no smooth in the ends of the tubules then the semi permeable membrane will never be moist. Which means that the gaseous oxygen and carbon dioxide cannot dissolve in to a liquid point out, and are thusly unable to diffuse into and from the cell, preventing cellular respiration from occurring. Which means that for slaters to survive in their habitat, there needs to be a fairly high % wetness, to ensure that the slaters don't desiccate and expire.

The respiration rate of your organism is directly related to its activity rate. If a person is more active, then it requires a greater amount of energy, and so the respiration rate rises. Due to the hygro kinesis of P. scaber, an orientation response in reaction to humidity, the activity of the slaters increased in lower % moisture, as they attemptedto move into a more suitable wetness. Thus the lowest % wetness, 33%, produced the average respiration rate of 0. 007804 ml of air per hour, the best respiration rate in the results. Then emerged 52. 9% moisture, producing 0. 0071 ml each hour, 76% moisture, producing 0. 006507 ml each hour, and 85% dampness, producing 0. 00543 ml each hour. Finally 93. 5 % dampness, the highest test, produced the lowest average respiration rate of the test, 0. 003017 ml per hour. When these results are graphed it becomes obvious that the effect of % wetness on the respiration rate of the slaters forms a non-linear regression development, showing a direct cause and impact relationship between the two variables, wetness being the reason, while respiration rate shows the effect. Thus we can easily see that the lower humidities produce respiration rates that are similar in proportions, which then get progressively smaller and less similar as the humidity increases. From this we can see that the change in respiration rate is not regular, but instead increases quickly as the dampness diminishes, before slowing and evening out. I think that an even lower humidity than 33% would show you that the pace of respiration eventually reaches a point where it stays the at the same level despite the continued decrease in % dampness, as the slater would reach its maximum respiration rate and therefore struggle to perform a larger amount of gas exchange than it already is. Thus the quantity of energy created from cellular respiration would stay at the same rate therefore would the activity rate of the average person.

Therefore it can be proven that the speed of respiration of P. scaber decreases as the % humidness of its environment boosts.

1. Moore R. C. and McCormick L. , 1969, Standard Top features of Crustacea, as cited in Explanations- Pseudotrachea, http://crustacea. nhm. org/glossary/define. html?term=Pseudotrachea

Evaluation: There were several controlled variables used in this test to ensure that the results obtained were valid and could be both analysed and talked about. Firstly, in conditions of equipment, all the tests were done using the same sized boiling tubes, bungs and graduated pipettes. This guaranteed that one sample of slaters didn't have a larger volume of air in their set up than another sample, and so all slaters possessed the same amount of oxygen available to them to execute respiration. In addition, it designed that no discrepancies in measuring the change in quantity occurred due to some pipettes using a different volume to others, as all pipettes got a ratio of 1 1. 8cm to 0. 1ml. The pipettes were fixed tightly in to the bungs in order that they were held steady, avoiding the pipette from moving which could have triggered fluctuations in the amount of drinking water in the pipette, which would have afflicted the validity of the results. All set ups were also remaining for the same amount of time before calculating the change in level, thus when the change in volume level in the test was assessed the variant in results was credited and then the respiration of the slaters and not to some tests being left working much longer than others. The amount of all saturated alternatives (magnesium chloride, magnesium nitrate, sodium chloride, potassium chloride, potassium nitrate) used in the tests was 1ml. This means that there have been enough of the solutions to produce the desired % humidity, however, not enough that there is surplus chemicals in the boiling tube to poison or elsewhere adversely impact the slaters in the test. It also means that no set up got more of the chemical than another, thus all experienced the same environment through the experiment except for the dissimilarities in % moisture. Ready ups also acquired the same type and amount of gauze. This recommended that the wrapping throughout the soda lime was the same thickness for ready ups, and so the same amount of carbon dioxide can undertake the gauze to be soaked up by the soda lime in all experiments, so that all experiments change in amount was not affected by less carbon dioxide being consumed by the soda lime than in other collection ups. While using same amount of gauze also means that the saturated solution's % humidness is able to filter to the rest of the boiling tube, as too much gauze would form a hurdle that would keep the air in the area including slaters at some other humidity from what was required for the experiment, and too little would allow the chemicals to drip through and damage the slaters. Thus having all experiments with the same amount of gauze means that the experiment is constant across all % humidities. The quantity of soda pop lime in each setup was 0. 2g. The consistent level of soda pop lime means that the amount was not large enough in any of the boiling pipes to soak up enough moisture from the environment to change the % wetness thus ensuring that the % wetness was steady across all set ups. The slaters which were used in the experiment were selected arbitrarily to ensure that the samples were an accurate representation of the population. These were all men and women, and of a similar size, because juveniles are much smaller than people and as such would require less oxygen for respiration, thus to help make the results valid I ensured that slaters found in the experiment were near one another in terms of size, and therefore age, so that their respiration rates would be similar. This shower that the experiment setup was put in was always at room temperatures. This is because colder drinking water would cause mid-air molecules to lose energy and the air to become denser, thus the quantity of water in the pipette would increase, diminishing the validity of the results by which makes it appear like more oxygen have been used for respiration than actually was. The opposite effect would take place in warmer drinking water, as mid-air would expand, giving a reading that was significantly less than it should have been, thus keeping the water at room temperatures helps to ensure the validity of the results. In each experiment there are 3 establish ups, enabling an average found. The experiment is repeated three times after that to provide your final average for everyone % humidities. This creates a fair test environment and a large enough sample range of slaters to be considered representational of the populace.

Before doing the test I assessed the % moisture and lux degrees of the slaters ecological market. This intended that I was able to firstly determine at what degree of light the slaters did not respond with image kinesis. This turned out to be 0. 17 lux, and I was therefore able to combine this into my method by within the test. Thus I made certain that the activity that would lead to an increase in respiration rate was credited only to the slater hygro kinesis, without picture kinesis being truly a factor. I found that the % humidness in their natural habitat was typically 87. 3%, and so whenever choosing my range of values for % humidity in my test I chosen 33%, 52. 9%, 76%, 85%, and 93. 5%. I didn't use a saturated solution of lithium chloride, as I determined the % moisture it triggered, 12. 5 %, was too low for long term contact with slaters as the difference from other habitat was large enough that it could almost certainly circumstance desiccation and death.

When I did so statistical research of my results I first put the final averages into a scatter graph when i was endeavoring to determine if there was a romance between % humidness and the respiration rates. Then i did the regression test, starting with the addition of a trend range. However a linear pattern lines produced an R2 value of 0. 6349, that was suprisingly low. However after looking within my tips again I attempted a non-linear regression. This fixed my points far better, offering an R2 value of 0. 9162. The R2 value can be an indication of how well the pints on the graph fit the brand, regarding my second graph, as shown earlier in the statement; the details fit the lines quite well, as the collection makes up about 91. 62% of the spread of the data. Non-linear regression means that the change in the independent variable (% wetness) causes a change in the dependant varying (respiration rate). Nevertheless the size of the changes aren't corresponding, in cases like this: in the bigger humidities the dissimilarities between respiration rates was greater than in the lower % humidities. Thus the statistical research shows that my results were not apt to be credited to chance, and therefore demonstrates the respiration rate of Porcellio scaber is influenced by the % humidity of the environment.

Thus my method and results were both valid, anticipated to my controlled variables, investigation in to the ecological topic and adaptations of the slaters, the number of repeats of the test done and the statistical research if the results.


Natural Record Museum of Los Angeles County, Explanations- Pseudotrachea, 11/4/10, found at http://crustacea. nhm. org/glossary/define. html?term=Pseudotrachea

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