Planarian Behavior Essay

Planaria belong to the class Turbella of the phylum Platyhelminthes. This paper depicts the behavioral reaction of Planarians to a variety of settings and compounds to better understand this particular Platyhelminthes. With a plastic syringe, it is possible to extract a sample of planaria, place into a Petri dish with enough freshwater and observe under a laboratory provided microscope. While on the microscope platform, expose your sample to light and darkness to notice the patterns of locomotion and movement throughout the conditioning tray. Probe the individuals with an object to spot any type of distinct change in response, negative or positive. Tap the side and surroundings of the dish to notice if there is any different adjustment in movement. Add sound to surrounding, noting any alter. Obtain a second sample, labeled separately, and use one dish to apply Hydrochloric Acid and the other to salt (NaCl) water. Note: Only using minimal amount or as needed. Using the tools provided, cut an individual in half to discover if the subject dies or survives. In conclusion, the Planarian makes it choice by moving towards the darkened areas, favorably. When applied to light, the individuals fled towards the edge. Any sudden object, sound, or altering didn’t affect the objects intentions. After five drops of 6 mol HCl (aq), the sample died of very quickly; however, five drops of 6 mol NaCl (aq) did not kill off near as quick. It was applied directly to the conditioning trays. Introduction Members of the phylum Platyhelminthes have a worm-like shape. The Platyhelminth has a bilateral symmetry and meets any provided situation in an â€Å"aggressive, head-on approach. Cephalization, a specialism of the anterior end of the animal, can be depicted in the gathering of sensory arrangement and cluster of nerves, also known as the ganglia or its brain, in the head region. Many of the behaviors you will see are associated to increases in mobility, higher activity, and general increase in responsiveness† (Collins, Harker 1999). Most planarians are free-living and common in freshwater environments, also found in marine and terrestrial places. Two ventral nerve cords run the length of the body. Located in the anterior end are two eyespots which possess photoreceptors to detect any form of light. Normally, a planarian contains a gastrovascular cavity that provides space for digestion tracts and the circulation of nutrient throughout the body. The mouth is located on the ventral end, which is the site for both food digestion and/or the release of bodily wastes. â€Å"Planarians are able to regenerate from essentially any type of injury and present a novel system for the study of wound responses in regeneration initiation. Planarian regeneration requires adult stem cells called neoblasts and amputation triggers two peaks in neoblast mitoses early in regeneration† (Wenemoser, Reddien 2010). Planarians are highly recognizable due to their ability to regenerate from the smallest body part. Typically vary in color from grey, brown or black. They seemingly move about on the bottom of rocks or submerged vegetation. Many are negatively phototactic, which simply means they shy away from any form of light fixture. Each worm has both male and female reproducing organs; however, they are monoecious in that they are not self-fertilizing. The most common form is asexual. They appear for function mainly as osmoregulation, the control of the levels of water and mineral salts in the blood. Planarians must constantly eliminate excess water and are carnivores that feed primarily on protozoans and other small animals. What is a Planarians reaction to a light fixture or exposed directly? Does it affect them in any way? What is the difference in responses from light and darkness? By inserting objects to the planarians path, does it alter their behavior? What about exposing them to sound or movement? Does making the water more acidic or basic affect the health and/or behavioral responses? Which is more likely to kill or harm the sample individuals? What are some distinct or unique characteristics definite in the planarian body structure that can be easily observed from a laboratory microscope? Do the individual samples favor any tests performed over the opposite stimulus? What could cause the planarians to move the way they are observed? I feel that given the ecological surroundings the planarian can be discovered, I imagine that the exposure of light will overwhelm the samples tolerance since they become adapt to living underneath rocks, plants, and other submerged vegetation in marine and freshwater environments. Inserting objects would just be like adding an obstacle course, so I’m predicting they would maneuver and meander around the objects. Acid always seems to be, in most cases, more harmful than any bases or salt compounds, for this test I will be assuming the 6 mol HCl will dramatically harm, if not kill, any planarian currently living about the conditioning tray. After the 6 mol NaCl is added to the Petri dish, I’m sure it will have an effect on them to an extent, seeing that some Planaria are capable of living in marine waters. Due to the fact that every piece of evidence available via text or online source, many testimonies have been provided that planarian individuals favor shaded as opposed to exposed areas of sun light or artificial light sources. Right away it will be easily distinguishable as to which technique will provide the most responsiveness to behavior. I don’t feel that creating any type of sound or movement that could be applied directly to the sample will alter or change the reaction of the planarians provided, since they are encompassed inside containers near such activities no matter what or where they are designated to be. I feel the most advantageous examinations will be the light versus dark and adding chemical compound to the already steady pH water provided. Materials and Methods Materials that were included in this lab include at least nine individual planarians, one metric ruler, two probing tools, one laboratory scanning microscope, three Petri dishes and lids or watch glasses, a vile of 6 mol HCl, a vile of 6 mol NaCl, a plastic pipette, one pen and/or permanent marker, and one lab notebook. Other things that could be used include a thermometer and a magnifying glass. With a dropper, we transferred planarian from the culture dish to a Petri dish and were sure to add enough water so that animal could glide freely over a small area of the dish. Next, we drew and labeled the ventral nerve cords, pharynx, eyespots, ganglia and gastrovascular cavity (see Figure 1 to identify these particular structures). To perform this experiment, we placed a petry glass on the stage of the microscope to view through the scanning lens. First, measurements were taken to note the length of the various planaria. By turning the light fixture on and off, we recorded any and all movement. Then with the three planaria, we used the probing tools to cut the planaria in half and used three of the halves that were left to observe any form of regeneration in the water provided. The other three were placed to regenerate in a separate petry dish to ensure they did not mix together. Of the remaining six planaria, we placed three in separate petry glasses. One of the glasses was used to add five drops of 6 mol HCl and the remaining petry glass was used to add five drops of 6 mol NaCl. After applying the chemicals to the water, one at a time in order for accurate and precise recording, we noted any changes in mobility, reactions, color, and/or functions. Added obstacles to the paths of some of the planarian and slowly tilted the glass back and forth to create water flow and movement. This was to ensure we created or reenacted any type of ecosystem the planaria may exist in to allow for maximum behavioral responses to different scenarios. This allowed for the most of the laboratory experiment and the more tests performed provide more precise results. Results After placing three planarians into a single petry dish, I placed the watch glass onto the stage of the microscope to first indentify body structures, organs, and gain knowledge into the ‘normal’ behavior of a single planaria. Using the metric ruler, I was able to establish the average length of the planaria to be 10 mm in length. As the light fixture remained off, I took notice that all of the planarians in the glass performed and acted in similar ways. They were free-moving, covering all surface provided within the water. After turning the lighting fixture on, each planarian scurried towards the water’s edge only to be trapped within the area provided. It appeared to me as if they were trying to evade the light in search of a more suitable and sustainable environment. Next, I used the probing tool to create an obstacle to see if they reacted any different to a new placement. Unfortunately, that was not the case; they simply went around or avoided it all together. As I came towards the adding chemicals section of the experiment, I used the tool to cut the planarian in half, to prove the theory of regeneration. The anterior end went about as if it was barely affected; however, the posterior end was quite the opposite, yet it still possessed signs of life and locomotion to an extent. Then I went ahead and used the remaining six planarian to test for any type of ability to survival when introduced to hydrochloric acid and salt water. After separating the samples into even numbered dishes, I first applied five drops of six molar HCl to the first sample. This almost simultaneously killed all of the living organisms within the dish. Next, I placed the same amount of six molar NaCl to the last dish; however this reaction was much different. After directly applying the salt water, the planaria seemed to behave abnormal, increasing they movement and livelihood. I was surprised that it didn’t kill them off as the hydrochloric acid did. It was almost as if they began to adapt or tolerate the new conditions. My only thought was that since a small percentage live in marine ecosystems, they are able to live in such conditions to an extent or within a certain limit. To my surprise they managed to live throughout the entire procedure. See Table 1 and 2 Discussions Exposing the planaria to light went as anticipated. Before the lab even began, it was very evident that these organisms were more prone to darkness; hence the reason for finding them on the underside of submerged items. â€Å"Most planarians are also light-sensitive and in some, pigmented light-sensitive cells are clumped in two cups that serve as primitive eyes† ( Kobayashi 2008). The one thing that caught my eye was how quick they were to avoid and almost escape the direct light, was as if they were in grave danger. I was rather intrigued to discover that although these animals are able to regenerate, I still was having a hard time believing they would still live for reasons of doubt; but after separating the body parts into halves, it reminded me much of an earth worm. When you go to capture an earthworm from the ground, and you accidentally break them or rip them into halves, each halve squirms away as almost if unharmed or phased. The placing of obstacles came to no surprise. Just as for any living organism, if it comes across an object in its path, the organism finds other means of getting around or avoiding all together. If it didn’t suit the planarian, it moved on. When adding the hydrochloric acid, I could only think one thing. If acid was applied to our skin or in great quantities in our ecosystem, we are exposed to a very harmful substance and more often times than not cannot tolerate a highly exposure rate. As I began to reach the final drop of acid into the dish, the organisms inside already began to show signs of death or nearing the end of life all together. The sodium chloride, however, was a different story. I didn’t really know what to expect. It could have went one of two ways, either erratically change the behavior and response to such chemicals or merely phase them at all. Much like the HCl, they weren’t used to such components and surely didn’t accept it; but even after adding all of the substance, it seemed as if the planaria were able to still find ways to adapt or tolerate expose to it. Unlike the HCl, they were able to survive. Consluion The results did prove my hypothesis correct. The planarians behavior response to light was vastly affected to the amount of exposure to direct light. There was an increase in mobility, higher activity, and general increase in responsiveness when any form of light was applied to the sample. Adding obstacles didn’t take much affect on the individuals, it simply just made an inconvenience and planned around it. By introducing hydrochloric acid and sodium chloride, it created a whole new means of survival of the fittest. The hydrochloric acid instantly killed off all the planarian exposed to the chemical, much like I predicted. The sodium chloride almost seemed as if it left the sample unharmed. In conclusion, there are several things I would also have included to this experiment for more discoveries. Things such as increase or decrease in water temperature, measuring the temperature at given times to note any changes in response to the change. Also, maybe adding other types of aqueous solutions to the mix, or perhaps compound that would change the performance of the viewed planarian, such as caffeine.