Photoreceptor Telodendria Morphology and Connectivity in the Zebrafish Retina

  • Author / Creator
    Noel, Nicole C L
  • Photoreceptors (the light-sensitive cellular mediators of vision in the eye) are divided into two classes: rods, which are sensitive to dim light and responsible for vision in low-light conditions, and cones, which are sensitive to specific wavelengths of light, and are responsible for daytime and colour vision. Photoreceptors must relay information to other retinal neurons for light information to be modified and sent to the brain for interpretation. If photoreceptors are not connecting to, and communicating with, the appropriate cells, transmission of light information fails, and no image will be produced. Therefore, the connectivity amongst photoreceptors is critical to their function, as it underpins lateral inhibition and effective translation of stimuli into neural signals. Despite much work characterizing second-order interneurons in the outer retina, the synapses directly connecting photoreceptors have often been overlooked. Telodendria are fine processes that connect photoreceptor pedicles. They have been observed in diverse vertebrate groups, yet their roles in vision remain speculative. Here, I visualized and characterized telodendria via fluorescent protein expression in photoreceptor subtypes. I characterized short wavelength cone telodendria in adult and larval zebrafish retina. Additionally, in the larval retina, I investigated rod telodendria and UV cone telodendria in mutant and transgenic retinas with altered complements of cone types. In the adult retina, telodendria are twice as abundant and branch almost twice as often on blue cones compared to UV cones. Pedicles of neighbouring UV and blue cones typically converge into contiguous pairs, despite the regular spacing of their cell bodies. In contrast to adults, larval UV cone telodendria are more numerous (1.3 times) than blue cone telodendria. UV cone telodendria are not detectably affected by ablation of blue cones, and are reduced 2-fold in mutant larval retina with few UV cones. I thus saw no evidence that telodendria increase in number in the absence of their typical cellular neighbours. I also found that larval rod telodendria are less abundant than short wavelength cone telodendria. In summary, I describe the development and morphology of zebrafish photoreceptor synaptic connectivity towards appreciating the function of telodendria in visual signal processing.

  • Subjects / Keywords
  • Graduation date
    2017-11:Fall 2017
  • Type of Item
  • Degree
    Master of Science
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.
  • Language
  • Institution
    University of Alberta
  • Degree level
  • Department
    • Department of Biological Sciences
  • Specialization
    • Physiology, Cell, and Developmental Biology
  • Supervisor / co-supervisor and their department(s)
    • Allison, W. Ted (Biological Sciences, Medical Genetics)
  • Examining committee members and their departments
    • Waskiewicz, Andrew (Biological Sciences)
    • Sauve, Yves (Ophthalmology and Visual Sciences)
    • McDermid, Heather (Biological Sciences, Medical Genetics)
    • MacDonald, Ian (Ophthalmology and Visual Sciences, Medical Genetics)