Method
The choice chamber were set up by placing water at 20oC in two of the compartments, wetting the muslin deliberately in one of the compartments, and about 10 grams of CaCl2 in another compartment. This choice chamber was left for about 3 minutes to settle into the condition. 10 woodlice were placed in the choice chamber. A digital stop clock was started as soon as the woodlice have all been placed in the choice chamber. A photo of the choice chamber was taken from top after 5 minutes. The number of woodlouse in each compartment was recorded once the photos were developed. This procedure was repeated with a choice chamber set up with water at 0oC, 20oC, 40oC and 80oC, and then it was also repeated by covering the choice chamber with the specifically prepared OHP and shining with the 100 watts table lamp from above in order to give different lighting condition to each compartment. The table-lamp and the OHP were removed immediately prior to taking the photo.
Figures
Figure 1. Humidity. In this experiment the woodlouse were exposed to a gradient of humidity, from an extremely dry to a waterlogged surrounding. Most woodlice preferred a damp surrounding, but a few others liked the waterlogged surrounding. Only one was present in the dry part of the chamber.
Figure 2. Temperature of water. In this experiment the woodlouse were exposed to a gradient of water temperature immediately below, starting from 0oC to ~80oC. However, there seemed to be a fairly even distribution of woodlouse in all chambers except the 20oC one.
Figure 3. Luminosity. In this experiment the woodlouse were exposed to a selection of lighting conditions, from almost complete darkness to the brightness of a 100 watt table lamp 20 cm above. The woodlice have preferred a surrounding of dim lighting, covered with 80 gsm copier paper. (The luminosity under 80 gsm papers is approximately equal to drawing the curtains up on a dull/rainy day.)
Criticisms and Discussion (Possible Errors/Comments)
It was impossible to use the photographic technology since all practical work must be ceased by the end of an 80 minutes double period, and I did not possess a Polaroid, therefore a technique of drawing diagram was adopted instead. It was found that the woodlouse would actually settle down to a suitable surrounding unless it is irritated by external means, so this made the counting much easier as well.
In experiment 1, a woodlouse settled down in the dry part of the chamber, but it was quite near to the moist part. I think this is because there is a leak from the damp part to the dry part, because any water that may have evaporated from the damp part would diffuse towards the dry part thus making it slightly moist, so this woodlouse may have been attracted by this slight trace of humidity, but it doesn't want to get any damper.
In experiment 2, the woodlouse seemed to have a fairly even distribution throughout the chamber, but I was rather surprised to find that the most number was found in the icy part. The water below is exactly 0oC, (it is "melting ice"), but the woodlouse seemed to like it and settled down there. This is probably because it is winter when this experiment was performed, and by experience they have "learnt" that the icy part usually bears more food, for example. However, it is not known that if they actually learn from experience (a particular type of Asian ant can learn from experience and record signature of its "friends" by chemical means). This relation must be investigated further to reveal the conclusion. A fair number of them also settled down in the hot part of the chamber, perhaps because it is more humid than other parts, because hot water evaporated quickly. (It was noticed that the hot parts of the chamber had an unacceptably high level of condensation.) Another means of heating should have been used instead, perhaps an electric heating coil. The use of a heating coil may also drive away water, so Calcium Chloride must be allocated in all partitions to remove any excess humidity to keep the humidity constant. The temperature of the water at the start may have been well distributed, but the only one that had been kept constant is the 0oC, because the water at all other temperature loses heat too quickly, and by the end of the 10 minutes, the water temperature have changed dramatically, as can be readily seen in the results table. If a thermostatic means of heating (such as an electric heating coil with a thermistor) have been used, then it would have been possible to keep the temperature constant, but this may cause permanent damage to the woodlouse and the choice chamber.
In experiment 3, the woodlouse preferred the dim lighting rather than complete darkness, but two of them settled in the dark area. It was expected that they would prefer a dim area, because the lower temperature. However, they did not like the dark area, probably because of the nature of the aluminum foil. Aluminum is a metal and thus can transfer heat much more efficiently by conduction. This is probably why that it may actually be hotter under the aluminum foil than under the 80 gsm copier. A piece of black paper should have been used instead.
Because of the time limitation, it has been very difficult to do any short-term observation. I think the choice chamber should really have been left for about 5 minutes before woodlouse are allowed in, and a further 15 minutes must be elapsed before the photos may be taken. The photos may also be taken at 1 minute intervals between 10 and 15 minutes, and an average calculated. The procedure should really also be repeated with different samples of woodlouse (e.g. woodlouse from Biology, woodlouse from my own garden, and woodlouse from South of England, or even different types of woodlouse). That would have given us a more generalized result, rather than doing an investigation on "the Edinburgh Academy Biology Department's woodlouse's preference to the environment". Discussion and Conclusion
From the data obtained in this experiment, I conclude that wood lice’s preferences to its environment are mainly dependent on the humidity, but also partly dependent on the temperature and luminosity. No attempts have been made to keep the humidity constant in the temperature experiment, and the temperature is different when different lighting conditions are applied. Therefore, I think the primary factor is humidity. This confirms my prediction of a preference to a damp and damp surrounding; however, I was not able to say anything about the temperature, because in experiment 2, the humidity was changed accidentally by the use of hot water. Provided that they have plentiful of water supply, the other conditions don't really matter than much because they can always recover the lost water, but in a dry surrounding they would not be able to acquire any more water, thus making humidity a vital factor. But whether they like swimming in a pool of water, or just a high content of water in air awaits further investigation.
