Road to Research

Finding a Topic

Finding a topic is like a roller coaster. At the top of the roller coaster, you feel the thrill and excitement of finding a topic. When you go down the roller coaster and it's at the bottom, the thrill and excitement reduce to disappointment as the topic you found needs to be narrowed or there is no gap to research. My first topic was the effect of UV light exposure on the SMEDPTEN gene in planaria. Essentially, the SMEDPTEN gene is a gene that controls cell division and prevents the uncontrollable growth of cells. I wanted to research how altering this gene using UV exposure would affect the planaria. However, in the aftermath of my rollercoaster ride, there was not much research relating the SMEDPTEN gene to tumors, uncontrollable cell growth. Thus, I had to start all over again. This time I went on a new rollercoaster. I found the topic of memory retention in Planaria. Where memory in planaria is stored is not yet known so I had finally found a gap. This is what led me to my research question: What effect does UV light cause on the memory retention of planaria?

Previous Research

Previous research has been done on the effect of UV exposure on planaria regeneration. One study is Mirjana Kalafatić’s study. The present study aimed to determine the effects of UV-rays =253.5 nm on mortality, behavior, and changes observed in the two planarian species(Polycelis felina & Dugesia tigrina) in laboratory conditions. This includes a methodology of using 253.5 nm of UV to see the effects of it on planaria. Exposure to UV light caused planaria to have lighter pigmentation, more wounds, slower motion, and a wrinkled epidermis. After regeneration, irradiated planaria had the same behavior as normal planaria. Irradiation did not cause DNA damage as planaria were still able to regenerate and function. Mirjana’s study shows that UV light exposure still keeps the DNA of damaged cells in planaria. This allowed the planaria to regenerate. This is important to know because it is crucial to keep the planaria alive and their ability to regenerate even with UV exposure. Research has also been done on the memory retention of planria. In Zhang’s study, they found out whether sucrose (table sugar) causes withdrawal symptoms and reinforcing effects in planarians. They figured out that sucrose (table sugar) causes withdrawal symptoms and reinforcing effects in planarians, establishing a Conditioned Place Preference in planaria. This is important to note because a CPP test is a way to test memory retention in organisms. This further shows the gap in where planaria memory is stored. Combining UV exposure to damage the cells and testing whether memory resides in the cells or elsewhere is important to add to the scholarly conversation.

Planned Methodology

I plan to use the methodology used in Kenneth Samuel's study.

Conditioned Place Preference (CPP): when a subject comes to prefer one place more than others because the preferred location has been paired previously with a reward (in this case it will be sucrose).

Pre-Exposure Control Group: Before UV exposure, baseline measure of memory for your planaria in a neutral environment, ensuring they don’t have a pre-existing preference for the compartments. If they do, pair the unpreferred environment with the sucrose solution to induce addiction
UV Exposure: Expose planaria to UV light for 5 min in 253nm (Mirjana). Since UV light can cause cellular damage, ensure the exposure is not so long that it causes death or irreversible harm to the planaria.
Regeneration: After UV exposure, allow the planaria to regenerate (14 days) (they can regenerate lost body parts). This is crucial because it’s a way to see whether memory persists after tissue regeneration, which may provide insight into whether memory is stored in the cells or the brain.
Post-Exposure Testing: Once regeneration is complete, repeat the CPP test to assess memory retention. If planaria show a preference for the environment they were conditioned to like, it suggests memory was retained.
Control group (no exposure to planaria): 3 petri dishes
- - - - Smooth petri dish: spring water or 10% sucrose solution (if unpreferred environment)
      - CPP testing dish: both rough and smooth surfaces, water solution, used to test after regeneration to see if memory persists
      - Rough petri dish: spring water or 10% sucrose solution (if unpreferred environment), sand + silicone glue mixture for rough surface, used to establish a CPP in planaria (establish CPP test)
Exposure Group (exposure to UV after establishing CPP) : 3 petri dishes
- - - - Smooth petri dish: spring water
      - CPP testing dish: both rough and smooth surfaces, water solution, used to test after regeneration to see if memory persists
      - Rough petri dish: 10% sucrose solution, sand + silicone glue mixture for rough surface, used to establish a CPP in planaria (establish CPP test)
Same petri dishes mentioned in control group but with a 10% sucrose solution; has UV exposure after CPP and cutting of planaria.
- - - - Sucrose produces dopamine relating effects on planaria, meaning planaria prefer sucrose (Zhang 2013). This will help them pair the rough surface with the sucrose solution, establishing a CPP.

Example of how petri dishes will look (Samuel 2021).

Relevance

The memory retention of planaria is a topic that is still being studied to this day. There is much unknown about these creatures. My research aims to provide more information on how and where planaria retain their memory. Research on planaria memory retention can provide clues about the fundamental mechanisms of learning and memory that may be conserved across species, including humans. It could also influence the development of regenerative medicine. Scientists could develop ways to harness similar processes in humans, particularly when studying how nerve damage (or brain injury) might be repaired or even how lost memories might be restored.

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