The Effect of Light Exposure on How Different Strains of C. Elegans Learn

Overview

To investigate learning under stress, Caenorhabditis elegans were conditioned to an environmental threat of vibrations applied to their culture plates. C. elegans are transparent soil-dwelling organisms susceptible to DNA damage caused by ultraviolet light. Light exposure poses a survival threat that may influence learning in C. elegans. Wild type and neuroligin deficient (nlg-1) C. elegans were tested because the neuroligin deficiency decreases responsiveness to sensory stimuli and may play a role in learning. I hypothesized that nlg-1 mutant and wild type C. elegans would show different rates of learning when exposed to ultraviolet versus visible light. Cultures were prepared with five worms of equal age per plate. One plate of wild type and one plate of mutant C. elegans were exposed to each of the three illumination conditions: ultraviolet light, visible light, and darkness. After 20 minutes of light exposure, the learning process commenced with the wild type plate being tapped at 120 beats per minute for 20 seconds with the bare tip of an electric toothbrush held against the rim of the culture plate. There were multiple tapping periods with gaps of non-tapping for 25 minutes. Each plate received about 1000 taps in order to desensitize/habituate the worms to the tapping. After digitally recording this process with a stereo microscope at 30-40x magnification, reversals, where worms reverse direction in response to a tapping, were measured in worm lengths to see how the worms adapted to the tapping stimulus. C. elegans often reverse direction when they sense vibration as a survival method. Both strains of worms successfully learned, as shown by reversal distances decreasing over time. As shown by reversal distances decreasing over time, both strains of worms did “learn” at different rates, with the wild types appearing to learn more effectively in all three types of light exposure. It is unclear whether the source of the decrease comes partly from neuronal damage in the light or is from learning only. While more data still needs to be analyzed, the data supports the notion that there is a distinct difference in the rates of learning with the different lights and between the two strains, which can be potentially applied to human learning.

Competition history

• AJAS 2019 Category not listed

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