BSC 2011
12 October 2022
The Effect of Light Exposure on Planaria Regeneration.
Introduction
Regeneration is a common phenomenon in nature that involves the growth and
differentiation of stem cells. Some organisms can regenerate entire lost limbs, and some
organisms can even regenerate a new organism from just a fragment of its old body. However,
this is limited to mostly invertebrates and simple vertebrates such as salamanders and small
lizards. For example, some lizards can use undifferentiated cells to regrow their tails with
varying success rates depending on what conditions the lizards are subject to (Turgut et al.
2006).
For this experiment, light exposure will be the independent variable, and the dependent
variable will be the regeneration rate of a planaria. The experimenters choose these variables
because light exposure is proven by other researchers to be a significant variable that effects
regeneration in invertebrates. In a study that exposes planaria to different light wavelengths.
there is a marked difference in regeneration rates based on what kind light the planaria is
exposed to. This occurs because the light wavelengths directly affect the rate at which a cell's
transcriptional factors affects the planaria's stem cells. (Emarkov et al. 2020)
This experiment will utilize the planaria, Girardia tigrina, to test if light exposure
influences regeneration rates. This planaria species is found in shallow, aquatic environments and
exhibit negative phototaxis. Because of its powerful regenerative abilities, this organism is ideal
for this experiment. It can form a new body from fragments of its old body. G. tigrina is also
ideal for this experiment because it is relatively easy to take care of. They require small housing
space, a small amount of food, and do not need to be constantly watched (Inoue et al. 2004). The
hypothesis experiment's hypothesis is that if planaria are exposed to constant darkness, then the
regenerative rates will increase. This is a sensible hypothesis because G. tigrina exhibit negative
phototaxis, meaning that they prefer darker environments.