The general habitat of this type of Isopod is outdoors in moist areas, where they are surrounded with large amounts of plant material. This provides them with food, as they are scavengers that feed on decaying matter (Pest Management, 2004). Large populations can often be found under logs, compost piles or leaf litter. Since they are crustaceans, these organisms will perish if they are unable to obtain enough moisture from its surroundings.
Method:
Students were designated 10 Slater’s, each obtained from the same environment and location. Using an opened rectangular container, a cardboard divider was taken and placed inside the container at exactly halfway, creating two evenly sized chambers. In the cardboard, a hole/door like shape was created in the centre of the base to allow for the Slater’s to move freely between the two chambers. Using a lamp, one side of the chamber was positioned underneath it to create a “light” environment. The other chamber was wrapped in black garbage bag, until the chamber was completely dark inside, thus creating the “dark” environment. The 10w Slater’s where then taken, placing 5 crustaceans in each chamber. For 10minutes the Slater’s were recorded at 30second intervals, writing down how many Slater’s where present in both chambers. Once the 10 minutes was up, this was then repeated and recorded accordingly.
Results:
After placing the Slater’s equally in the two chambers of the containers, over time (10mintues) they migrated to the dark side. In all cases, the dark environment had higher migration rates than the “light” environment (figure 1 and 2). It was evident that the Slater’s preferred the “dark” chamber in both trials of the experiment. When comparing the results of the light and dark chambers, there was fluctuation during the 10minutes trials, at 4.30 and 5.00 in trial 1 and 5.30 and 6.00 in trial 2 the numbers in both chambers where more even, however still favored the dark side. At other times however, 3.00, 7.30, and 9.00 in trial 1 and 2.30 and 3.00 in trial 2 (figure 1 and 2 respectively), the numbers favored the dark side almost completely.
Overall, from this experiment, Slater’s preferred a “dark” environment as opposed to a “light” one.
Discussion:
When comparing the results of the light and dark environments, Slater’s favored the darker Habitat. Once the Slater’s were placed into each chamber, they began to migrate to the darker side almost straight away (Figure 1). At 0.30min/sec, there were 6 to 4 Slater’s, dark to light respectively, and by 1.00min/sec, there were 8 Slater’s out of 10 in the dark chamber (figure 1). Figures continue to stay relatively high throughout the 10minute block which tells us that Slater’s seem to prefer a darker environment. However, due to human error, one cannot conclude from just this 1 trial. A second trial was undertaken, showed similar results (figure 2).
For an experiment to give the best possible outcome, repetition needs to be undertaken. Human error can occur and alter results, therefore giving false information. When undertaking this experiment, there were a number of things that could have altered the outcome. The size of the “doorway” should have been measured, ensuring all Slater’s were small enough to move freely between both sides of the container, as Slater’s vary in size and larger ones were present. Also, when the lamp is used over the lighter chamber, it gave off heat, therefore not giving accurate results due to testing other stimuli, temperature. If repeated again, by changing the light source and “doorway” for the Isopods, a better understanding of a Slater’s response to light could be established.
The response of some isopods towards light, is closely linked to the microclimatic conditions prevailing within their habitats (). Slater’s exhibited negative photo taxis, they moved away from the light, this shows not only a preference for a dark environment but could also show that they were persuaded to the dark due to other factors that are associated with darkness, for example humidity and temperature. It is apparent that with light environments higher temperatures and low humidity are evident () As these Terrestrial Isopods prefer a more humid condition, they would tend to stay clear of these sorts of environments.
Slater’s tend to form their habitats in moist, humid conditions (Massey, 2011) Isopods abdominal legs are modified to form thin, plate-like gills (Massey, 2011). For these gills to function properly they need to remain covered with a thin film of water, which is why Slater’s prefer these damp, sheltered type of conditions (Massey, 2011). As seen in any sheltered environment, darkness is always present to a certain degree. Therefore, when the Slater’s migrated into the darker chamber, one is unable to completely determine whether the Slater’s themselves are assuming water and humid conditions will be present. Therefore light being an insignificant factor.
Conclusion:
During this experiment of testing Isopods response to certain stimuli, light, it was observed these Terrestrial Isopods prefer a dark environment. Over the 2 trials conducted, there was an obvious preference demonstrated, with over 60% at all times favoring the darker chamber (figure 1 and 2). Due to Isopods having plate-like gills on their legs that they need to keep moist, it could be concluded that Isopods need a humid and moist environment to be surrounded by. Therefore as lighter environments imply higher temperatures and low humidity (Warburg, 1964), Isopods prefer a darker environment.
Figure 1: Slater’s response to Light Trial 1
Figure 2: Slater’s response to Light Trial 2
References:
Using Live Insects. (1997). University of Arizona Center for Insect Science Education Outreach July 26, 2004.
Powell, Peggy K. (2000). West Virginia University Extension Service . Sow bug and Pillbug household
Pest Management 9004. July 11, 2004.
Massey, U. (2011). Isopoda [Internet Article ]. Guide to NZ Soil Invertebrates
Warburg, M. R. (1964). The response of isopods towards temperature, humidity and light. Animal Behaviour, 12(1).
