Date of Defense
4-18-2024
Date of Graduation
4-2024
Department
Biological Sciences
First Advisor
John Jellies
Second Advisor
John Spitsbergen
Abstract
Leeches, along with many other animals have developed defense mechanisms from harmful Ultraviolet light (UV). These behaviors are observable, but the neuronal pathways that coordinate these mechanisms are unknown. In this study, the Retzius neurons, a pair of interneurons in the central nervous system of the leech, are tested to reveal a response to UV light with regards to spatial presentation. Two different semi-intact dissections were performed with one preparation having a cephalic nerve cord cut, and the other having a caudal nerve cord cut. This allowed for inputs to be solely processed by the caudal sensilla and the cephalic sensilla, respectively. Four LED flashlights of different wavelengths that represent red, green, blue, and UV light were used to stimulate the photoreceptors on the caudal end and the head end of the leech. Extracellular recordings of the S cell and intracellular recordings of a Retzius neuron were taken before and after stimulation. The Retzius neurons displayed a tremendous response to UV light when receiving input from the tail and had little to no response to UV light with stimulation of the cephalic end. The cells showed no response to visible light for either preparation. These results are consistent with previous findings detailing the differing mechanical escape responses elicited from UV light. The results of this study support the idea that the Retzius cells are a part of the neuronal pathway that coordinates the escape response from the tail end of the leech. The data also shows that the Retzius cells are differentially activated by UV light as opposed to visible light. This knowledge helps to contribute to the overall understanding of neuronal pathways and how UV stimulus affects behavior.
Recommended Citation
Sirrine, Gwenyth, "Interneurons Distinguish Between UV & Green Light Depending Upon Spatially Relevant Inputs in H. verbana" (2024). Honors Theses. 3845.
https://scholarworks.wmich.edu/honors_theses/3845
Access Setting
Honors Thesis-Restricted
Restricted to Campus until
6-19-2025