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The main goal of this research was to increase our understanding of eye biology and the genes that are involved in planarian phototransduction. Planarian flatworms, which are best known for their unique regenerative abilities, demonstrate a well-documented photophobic response to light, but not much is known about the mechanisms behind it. A light assay was created and used to determine that planarians show varying behavioral responses to different visible wavelengths, ranging from long to short (red: 615-640 nm, green: 515-520 nm, blue: 460-470 nm). This research also showed that planarians display behavioral responses for non-visible wavelengths on separate ends of the spectra (infrared: 700-850 nm, and 2 wavelengths of ultraviolet light: 395-405 nm and 360-365 nm). Behavioral responses occurred in a hierarchy, with shorter wavelengths causing more severe photophobia. Furthermore, like many aquatic animals planarians possess not only ocular (visual) phototransduction but dermal (through the skin) phototransduction as well. Since nothing is known about the mechanisms that regulate planarian dermal phototransduction, genes with the potential to regulate dermal phototransduction were cloned and analyzed. Non-full-length gene sequences were cloned for each candidate using standard protocols. Once inserted into expression plasmid vectors, the constructs were used as templates for generating double-stranded RNA (RNAi). Following RNAi knockdown (via feeding of double-stranded RNA) to each individual gene candidate, the planarians were tested for their photophobic responses with the previously designed light assay. Of the genes tested, only TRPA1 was found to be required for the dermal photophobic behavioral responses in planarians (as worms without TRPA1 had significantly reduced responses). These data suggest that phototransduction in planarians is more complex than previously thought.
Bacher, Jessica, "Investigating Ocular and Dermal Phototransduction in Planarian Flatworms" (2016). Honors Theses. 2696.