Girardia Tigrina: Introduction and Methods

Regeneration is defined as “revival or renewal”. Such meaning is not far off from the scientific use, in biology, regeneration is the reactivation of development in later life in regard to restoring missing tissues. The possibility that scientist could reverse damaged tissues in specific species has caused a new focus on organism’s that demonstrate regenerative qualities. Regeneration can occur through the use of specific types of cells. Pluripotent cells are embryonic stem cells that have the “potential” in creating/ regenerating a completely new organism.

They trigger the formation of basic layers of tissues, ectoderm, mesoderm, ectoderm. These layers create functioning tissues within an organism. The understanding and exploration of regeneration can impact the future of human regeneration ranging from organs to potential developed and functional limbs.

The variable that is being tested is the growth over time of the amputated area. The focus of regeneration is dealing with damaged tissue. Stem cells shift into affected areas of amputation during regeneration.

Moreover, before amputation, a majority of stem cells are stationary in one section. Following amputation, the stem cells shift in directional flow during regeneration to restore long-term tissue homeostasis. In select organisms amputation of the head can slow down the process of regeneration due to the given time that stem cells need in order to arrive at the area of decapitation . Furthermore, in order for regeneration to occur factors such as time should be accounted for. Time is necessary for stem cells to arrive at the amputated area and commence the process of regeneration.

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The organism chosen for the study of regeneration is Girardia tigrina (Planaria) a type of platyhelminths from the Turbellaria class. These small worms have the capacity to regenerate at a quick, and efficient time frame. In Girardia tigrina the area of amputation triggers a neoblastic response to occur, in which the organism body focuses on leading neoblast to the damaged area . This neoblastic response triggers the division of neoblast which lead to the regeneration of new tissue. Girardia tigrina research has been influential into understanding regeneration of other organism and how an organism elicits the formation of new tissue following amputation. Giardia tigrina regeneration has experimented with pluripotent stem cells(neoblasts).

An important organ within Girardia tigrina is the pharynx, the main digestive system that processes the food within the planarian’s stomach. Girardia tigrina can reproduce asexually as tested from our current experiment. Although so, they have the capacity for sexual reproduction. As stated neoblast within the Planaria are found in 30% of the body making them ideal for regeneration. Girardia tigrina can re-grow a complete organism even without needing to cut the entire head. The neoblast function as pluripotent cells that can rebuild reconnective cell tissue. In order for regeneration to occur faster, a cut should be made above the pharynx. The piece containing the pharynx will regenerate faster the piece lacking it.

Commencing with the experiment the six Girardia tigrina were taken from a population enclosed in well water at room temperature. All six Girardia tigrina were alive and taken from the population by transfer to a different habitat. The new habitat in which was presented as a compact case with twelve individual sections. Each section was filled with well water to keep the Girardia tigrina from dying. Each individual Girardia tigrina was picked up by a plastic transfer pipette and placed on top of a microscope glass. A razor was used to amputate the head of the Girardia tigrina right above the pharynx. Then each half was placed in separate sections inside the case filled with a small amount of well water. Six sections labeled “head” and six bottom sections labeled “body”. At the start of the experiment, Six Girardia tigrina were fed for egg yolk for thirty minutes.

After the initial feeding and amputation, the heads and bottoms were once again separated into their corresponding sections. For two weeks, the Girardia tigrina were fed egg yolk for 20-30 minutes at room temperature. It was imperative that the temperature remained the same at room temperature in order to avoid impending disruptions in the organism natural state. After each feeding, the well water was changed following measurement for the corresponding day by taking an image of their size in cm and then compared it to the measurement of the previous week. The image helped to track their progress as well as to acknowledge their livelihood. The images were analyzed in order to compare in order to compare and measure their growth. ImageJ allowed us to measure the length of the Girardia tigrina by counting the pixels (cm) from one end to the other. After comparing photos from each organism within the trial; the population shifted from twelve to thirteen Girardia tigrina (one organism asexually reproduced). These images demonstrated regeneration within the two samples (heads vs tails).

Work Cited

1. Eisenhoffer, George T., Hara Kang, and Alejandro S. Alvarado. Molecular Analysis of Stem Cells and their Descendants during Cell Turnover and Regeneration in the Planarian Schmidtea Mediterranea. vol. 3, , 2008, http://www.sciencedirect.com/science/article/pii/S1934590908003366, doi://doi.org/10.1016/j.stem.2008.07.002.
2. Tanaka, Elly M, and Peter W Reddien. The Cellular Basis for Animal Regeneration. vol. 21, , 2011, http://www.sciencedirect.com/science/article/pii/S1534580711002504, doi://doi.org/10.1016/j.devcel.2011.06.016.
3. Wenemoser, Danielle, and Peter W. Reddien. Planarian Regeneration Involves Distinct Stem Cell Responses to Wounds and Tissue Absence. vol. 344, , 2010, http://www.sciencedirect.com/science/article/pii/S0012160610008377, doi://doi.org/10.1016/j.ydbio.2010.06.017.
4. Guedelhoefer, Otto C., and Alejandro S. Alvarado. ‘Amputation Induces Stem Cell Mobilization to Sites of Injury during Planarian Regeneration.’ Development (09501991), vol. 139, no. 19, 2012, pp. 3510 3520, http://search.ebscohost.com/login.aspx?direct=true&db=a9h&AN=80410483&site=ehost-live, doi:10.1242/dev.082099.
5. Sedeer el-Showk. ‘Unravelling how Planaria Regenerate” 2014, https://www.nature.com/scitable/blog/accumulating-glitches/unravelling_regeneration_in_planaria.
6. Gilbert, Scott F. “Developmental Biology.” Current Neurology and Neuroscience Reports., U.S. National Library of Medicine, 1 Jan. 1970, www.ncbi.nlm.nih.gov/books/NBK9983.