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How do Stemmata Grow? The Pursuit of Emmetropia in the Face of Stepwise Growth

Werner, Shannon

Abstract Details

2014, MS, University of Cincinnati, Arts and Sciences: Biological Sciences.
However complex or atypical the visual system, all of its components the lens, eye size and shape, retina and nervous system - must be well tuned to one another. As organisms grow, their eyes must be able to achieve and maintain emmetropia, a state where there is a good fit between the optical and receptor portions of the eye. Based on vertebrate studies, emmetropia is accomplished through a combination of initial regulation by genes, followed by homeostatic visual input from the environment for fine-tuning. How quickly and effectively emmetropia can be achieved will influence the ability of an animal to execute visually guided behavior. While there has been ample research into how vertebrates manage eye growth toward emmetropia, this has never been addressed in arthropods, which develop in a stepwise fashion through ecdysis. Of particular interest are larval holometabolous arthropods with camera type eyes, called stemmata in larval arthropods. Stemmata, such as those of the larval eyes of the Sunburst Diving Beetle (Thermonectus marmoratus, Coleoptera, Dytiscidae) must recover emmetropia after ecdysis, developing a well formed lens and receptor components that are well tuned to the lens’ optical properties. Here I use this system as a model for measuring when and where eye growth toward emmetropia occurs around different molting periods. Histological and optical techniques were used to investigate growth of the principal larval eyes of T. marmoratus. These studies revealed that larval eye tubes grew significantly within the first hour after molt, with the crystalline cone contributing the most to overall growth. Lenses were slower than the eye tubes to reform, regaining the ability to project sharp, distinct images eight hours after molt. Further osmotic experiments using immersion in hypotonic (water) or hypertonic (100% insect Ringer’s) solutions explored water uptake as a potential mechanism of growth. Preliminary data showed significant differences in the change of eye tube length for eye two between individuals exposed to water and Ringer’s solution. These results are the first demonstration of how holometabolous arthropod stemmata grow and change after a molt. Specifically notable is that the eye tube and optical components grow very rapidly, within the first hour, before the lens is capable of image formation. Results also show that within the first day after molting, larval eyes already regain functional emmetropia, and that water uptake within the eye via osmosis may be vital to the rapid growth of these larval eyes. I anticipate that this first exploration of how stemmata grow after molting will open new avenues of investigation in other arthropod camera type eyes or investigations into comparisons between post-ecdysal camera type eye development in aquatic arthropods land based land based arthropods. Additionally, preliminary evidence of osmosis as a potential mechanism of growth may provide a basis for a thus far unknown mechanism for invertebrate eye growth. Further investigation into water regulation in vertebrate and invertebrate eyes as a mechanism for growth and fine-tuning are warranted.
Elke Buschbeck, Ph.D. (Committee Chair)
Tiffany Cook, Ph.D. (Committee Member)
John Layne, Ph.D. (Committee Member)
50 p.

Recommended Citations

Citations

  • Werner, S. (2014). How do Stemmata Grow? The Pursuit of Emmetropia in the Face of Stepwise Growth [Master's thesis, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1416570855

    APA Style (7th edition)

  • Werner, Shannon. How do Stemmata Grow? The Pursuit of Emmetropia in the Face of Stepwise Growth. 2014. University of Cincinnati, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1416570855.

    MLA Style (8th edition)

  • Werner, Shannon. "How do Stemmata Grow? The Pursuit of Emmetropia in the Face of Stepwise Growth." Master's thesis, University of Cincinnati, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1416570855

    Chicago Manual of Style (17th edition)