Behavioral Studies of Pillbugs - Research Paper Example

Abstract Behavioral Studies on Pill Bugs The common pill bug, of the scientific name Armadillidium vulgare and of the order Isopoda, is an interesting animal whose behavior changes as its environment is manipulated. The findings regarding the behavior of pill bugs will shed light on human psychology as well especially when it comes to feeding, sheltering and problem solving. Based on a study by Refinetti (2000), the pill bug must possess an endogenous circadian pacemaker that does help it distinguish light from dark environments. Nevertheless, this mechanism is actually considered very weak and this is actually not tied up to mechanisms for locomotor activity in the pill bug. This therefore implies that pill bugs may not necessarily move towards a dark area. This somehow opposes the previous finding that pill bugs exhibit a strong negative phototaxis or an attraction to places with very little or not light at all. Moreover, it has been concluded in the study that the locomotory activity of the pill bug is most likely not due to their internal reaction to the effect or absence of light but due to negative masking, or the mere distinct effect of light that one can observe when a pill bug cannot escape the lighted area. Moreover, the attraction of pill bug towards dark areas is somehow not due to their reaction to light but because of their “strongly nocturnal activity under a natural light-dark cycle, more or less controlled by an endogenous timer” (Drahokoupilova & Tuf, 2012, p. 153). External marking agents may also cause an internal effect on the behavior of pill bugs as the marked pill bugs exhibited more hiding behavior during the day and exploratory activities limited to night time. Moreover, marked pill bugs were usually significantly less active due to the mark, and that they have a lower level of feeding. The alleged connection is mostly chemical as “some chemicals from polish and marker might break through the cuticle into haemolymph of pill woodlice…” (Drahokoupilova & Tuf, 2012, p. 152). When it came to their feeding habits, the pill bug spent more time in high quality food patches compared to those with low quality. However, as the high quality food becomes less in amount and the distance between the pill bug and the potential sources of food becomes greater, the pill bug, just like any other animal, will tend to conserve its energy and will tend to feed on low quality food that is currently available (Tuck & Hassall, 2004). Therefore, whenever foraging or feeding of pill bugs is considered, it should be observed whether distance is a significant factor in determining their preference for high quality food. In a study by Moriyama (2004) on the movement of pill bugs, those which are constantly subjected to physical stimulus, especially one triggered by another pill bug, will be interpreted by the organism as a problematic situation and will most likely result in autonomous behaviors such as “mounting “ and “death-feigning behaviors” (Moriyama, 2004, p. 287). However, these autonomous behaviors are not an effort of the pill bug to escape the situation and choose suicide in the long run, but to find a vehicle to get out of the situation and to avoid the constant pulling stimulus. Therefore, since there is no vehicle, the pill bug chooses to “mount” in order to use the other one as a “transportation vehicle,” and to display death-feigning behavior in order to use the other pill bug as a “traction” vehicle (Moriyama, 2004, p. 300). The important point made by Moriyama (2004) in his study is that the pill bug never fails to move or to find the means to reduce the frequency or intensity of the bothersome stimulus. Moreover, according to Moriyama (2004), this behavior of pill bugs is attributed to their robust homeokinetic living system, and so these species of animals never fall into a state where they cannot move anymore and so they are quick at organizing and reorganizing behavior. In short, pill bugs will naturally move around and when it is mounting or feigning death, it only it could only mean that it wants to move around and that a stimulus is blocking its way. According to Hassal and Tuck (2007), when it comes to shelter, the pill bug preferred more the grazed rather than the ungrazed swards, but oftentimes exhibiting intermediate levels of grazing. Moreover, the pill bug naturally prefers rainfall and higher soil temperature. However, relatively high amounts of rainfall may cause mortality in the pill bug and sudden and great fluctuations in temperatures like changes of as much as 25°C may also kill populations of pill bugs. Based on the aforementioned theories, this study therefore investigated whether pill bugs will behave according to the findings of previous studies. For the first experiment, it was investigated wherein pill bugs would demonstrate mounting more than move around with each other. This is based on the idea that the repetition of an unavoidable and uncomfortable physical stimulus would naturally make the pill bug use another as a vehicle to facilitate movement (Moriyama, 2004). In the second experiment, it was determined whether pill bugs would distribute themselves evenly within a prescribed space and between two containers. This is based on the theory that the pill bug possesses a robust homeokinetic living system (Moriyama, 2004). In the third experiment, it was determined whether pill bugs would prefer wet to dry environment. This is based on the theory that the pill bug has a special affinity to rainfall (Hassal & Tuck, 2007). The fourth experiment tried to find out whether pill bugs preferred darkness to light. This is based on the findings which state that the pill bug exhibits phototaxis and is inclined towards nocturnal activity (Refinetti, 2000; (Drahokoupilova & Tuf, 2012). Lastly, the fifth experiment tried to determine whether pill bugs would prefer an environment with good quality food like chia seeds. This is based on the idea that pill bugs would naturally prefer good quality food as long as it is available at a relatively close distance (Tuck & Hassall, 2004). Method The subjects used were 60 pill bugs, 10 bugs for experiments 1 and 5, while 50 for experiments 2, 3 and 4. Moreover, they were taken from Carolina Biological Supply Company. These pill bugs had no tails and rolled up in a ball. The pill bug was Armadillidium vulgare. It belonged to the family Armadillidiidae, Phylum Arthropoda, Order Isopoda. For each of the five experiments, the materials used included plastic petri dishes with cover and white filter paper. For each of the five experiments, we observed pill bugs for 10 minutes as they were moving in a plastic petri dish. We also defined 7 behaviors of pill bugs: locomotion (LO), which refers to movement around the chamber and even the movement of its antennae; mounting (MO), or climbing on top of another pill bug; resting (RE), or the absence of movement for at least 3 seconds; curled (CD), or the state where the pill bug exhibits no mention or when it is rolled into a ball; curling (CL), or when the bug is on its back while moving its legs; flailing (FL), or the situation where the pill bug is upside down; and not visible (NV), when the pill bug is located between two chambers. For the first experiment, what was needed was the percentage of pill bugs that spend their time mounting. The hypothesis was that the bugs would exhibit more mounting than free movement in the prescribed area. In order to do this, 10 pill bugs were placed on the petri dish and were observed for 5 minutes while scanning their behavior every 30 seconds. The second experiment determined whether pill bugs would distribute themselves evenly within a prescribed space and between two containers. They are expected to evenly distribute themselves in the two petri dishes. We had two petri dishes connected so that the pill bugs could move freely from one petri dish to another. In the third experiment, it was determined whether pill bugs would prefer wet to dry environment. The hypothesis was that the pill bugs would be attracted to the wet petri dish. We placed wet filter paper on one of the petri dishes and a piece of dry paper on another. The fourth experiment tried to find out whether pill bugs preferred darkness to light. This is based on the findings which state that the pill bug exhibits phototaxis and is inclined towards nocturnal activity. Chamber B of the petri dish was covered with a piece of black cloth. Then the number of bugs that stayed in the dark part was counted against those that stayed in the light. The fifth experiment was supposed to find out whether pill bugs would naturally prefer good quality food as long as it is available at a relatively close distance, therefore, it was expected that the pill bug will go to the area of the chia seeds. Wet chia seeds were place in chamber A, and we scanned the behavior of the bugs every 1 minute for 10 minutes. Results Based on the aforementioned theories, this study therefore investigated whether pill bugs will behave according to the findings of previous studies. For the first experiment, it was investigated wherein pill bugs would demonstrate mounting more than move around with each other. Based on the results, the chi-square value is 13.075, which means that there is no significant difference between the number of pill bugs that mount another, and those that did not. Nevertheless, the fact that there is an average total of 0.5 of those that mounted and 9.5 of those that did not – somehow tells us that mounting is not really a natural instinct of a pill bug, or perhaps the space was too free and so there was really no need for mounting. The second experiment tried to find out whether pill bugs would distribute themselves evenly within a prescribed space and between two containers. In the study, the pill bugs are expected to evenly distribute themselves in the two petri dishes. The chi-square result for this experiment is 5.78, which means that there is no significant difference between the number of bugs that distributed themselves in A and those that did in B. Somehow, the idea here is that there must not be any difference between the number of bugs in A and that in B because the expected distribution is even or equal. However, the totals, 16.5 and 33.5 respectively for A and B, somehow suggest the possibility of unequal distribution. In the third experiment, it was determined whether pill bugs would prefer wet to dry environment. The hypothesis was that the pill bugs would be attracted to the wet petri dish. The chi-square result for this is 14.1512, which means that there is a significant difference in the preference of pill bugs on the wetness or dryness of environment. This means that truly, pill bugs really prefer wet places and does not go for dry ones. Moreover, even the average total results say so: 38.3 and 11.7 for the wet and dry places respectively. The fourth experiment tried to find out whether pill bugs preferred darkness to light. This is based on the findings which state that the pill bug exhibits phototaxis and is inclined towards nocturnal activity. The chi-square value for this is 1.2168, which means that there is no significant difference between A and B. This means that considering the values of 21.1 and 28.9, as totals, the idea is that it may not be true that pill bugs move towards the darkness nor avoid the light. The fifth experiment was supposed to find out whether pill bugs would naturally prefer good quality food as long as it is available at a relatively close distance, therefore, it was expected that the pill bug will go to the area of the chia seeds. Based on the chi-square value for this experiment, 3.844, it means that, for pill bugs, there is a significant difference between those who prefer white chia seeds as food and those who don’t. In fact, the totals at 8.1 and 1.9 respectively acid for those that eat, wet, chia seeds and those that do not. Discussion The first experiment investigated wherein pill bugs would demonstrate mounting more than move around with each other. The basis for this is the theory that the repetition of an unavoidable and uncomfortable physical stimulus would naturally lead to mounting behavior among pill bugs in order to use the mounted bug as a vehicle of transport (Moriyama, 2004). The hypothesis therefore was that the bugs would exhibit more mounting than free movement in the prescribed area. The experiment yielded five instances of mounting while the rest of the trials, the pill bugs did not mount. Moreover, this was not a significant activity, perhaps because the space the wire the pill bugs were may have been relatively enough for free movement. This naturally did not trigger any deliberate acts of mounting, but perhaps only coincidental. Nevertheless, if the bugs had been placed in a smaller container, mounting may have occurred deliberately and more frequently. The second experiment determined whether pill bugs would distribute themselves evenly within a prescribed space and between two containers. The theory by Moriyama (2004) serves as the basis for this: that the pill bug possesses a robust homeokinetic living system, thus they are expected to evenly distribute themselves in a particular space or area. In the third experiment, it was determined whether pill bugs would prefer wet to dry environment. The theory upon which this was based is that the pill bug has a special affinity to rainfall (Hassal & Tuck, 2007). In the actual experiment, only 2.4 out of 10 that went by to the dry Side B. The fourth experiment tried to find out whether pill bugs preferred darkness to light. This is based on the findings which state that the pill bug exhibits phototaxis and is inclined towards nocturnal activity (Refinetti, 2000; (Drahokoupilova & Tuf, 2012). Based on the results of the experiment, an average of 3.6 out of 10 bugs preferred the light while an average of 6.4 preferred the dark. This may somehow mean that pill bugs naturally prefer darkness to light when it comes to their habitat and any place that they explore. However, based on the results of the standard deviation, there is no significant difference between the preference of the pill bug to either dark or light. This could be attributed to the fact that the locomotory sense of the pill bug is generally not considered connected with its perception of light and darkness (Refinetti, 2000). Lastly, the fifth experiment tried to determine whether pill bugs would the idea that pill bugs would naturally prefer good quality food as long as it is available at a relatively close distance, therefore, it is expected that the pill bug will go to the area of the chia seeds (Tuck & Hassall, 2004). Based on the results of the experiment, an average of 7.2 out of 10 bugs preferred the area with chia seeds while only 2.4 out of 10 chose not to. Based on the results of the statistical analysis and based on the results of the experiment as well, pill bugs prefer wet food. For pill bugs, the significant differences lie only in two aspects, preference for wet places and wet food. This is consistent with the theories that say that the pill bug generally looks for food in wet places and that they usually go for a wet environment. This study must improve in a few aspects. First, a larger number of pill bugs should be used. Second, the same thing should be tried in all types of insects or isopods. Third and lastly, one should consider investigating the validity of the procedure for the various experiments which yielded an absence of significant difference. References Drahokoupilová, T., &Tuf, I. (2012).The effect of external marking on the behaviour of the common pill woodlouse Armadillidiumvulgare.Zookeys, 176, 145-154. doi:10.3897/zookeys.176.2375 Hassall, M., & Tuck, J. M. (2007).Sheltering behavior of terrestrial isopods in grasslands.Invertebrate Biology, 126(1), 46-56. doi:10.1111/j.1744-7410.2007.00075.x Moriyama, T. (2004). Problem solving and autonomous behavior in pill bugs (Armadillidiunvulgare). Ecological Psychology, 16(4), 287-302. doi:10.1207/s15326969eco1604_2 Refinetti, R. (2000). Circadian rhythm of locomotor activity in the pill bug, Armadillidiumvulgare (Isopoda). Crustaceana, 73(5), 575. Retrieved from http://www.brill.com/crustaceana Tuck, J. M., & Hassall, M. (2004). Foraging behaviour of Armadillidiumvulgare (Isopoda: Oniscidea) in heterogeneous environments. Behaviour, 141(2), 233-244. doi:10.1163/156853904322890834 Read More