Date of Completion

8-9-2019

Embargo Period

8-9-2019

Keywords

Firefly, Photuris, Vision, Stemmata, Rhabdomere, Optic Nerve, Behavior, Photo-activity

Major Advisor

Andrew Moiseff, Ph.D.

Associate Advisor

Joseph Crivello, Ph.D.

Associate Advisor

Rahul Kanadia, Ph.D.

Associate Advisor

Marie Cantino, Ph.D.

Associate Advisor

Charles Henry, Ph.D.

Field of Study

Physiology and Neurobiology

Degree

Doctor of Philosophy

Open Access

Open Access

Abstract

Fireflies are bioluminescent beetles and members of the holometabolous clade. As holometabola, fireflies interact with their environment during two stages: larva and adult. I studied firefly stemmata, Photuris genus, with the aim of understanding their ecological utility by identifying structural and functional features of the eye. As a first step toward this goal, I used microscopy to characterize the architecture of firefly stemmata. I concluded that Photuris eyes were a type of fusion-stemmata, evidenced by a bi-lobed organization. Each eye contained 88 photoreceptors that contributed dense interlocking-microvilli forming a fused-rhabdom. In the next section, I tested whether stemmata regulated photo-dependent activity. I found that larvae were more active during nocturnal conditions, but unexpectedly, these behavioral patterns were not sufficiently explained by stemmata. Upon excision of the optic nerve, larvae maintained their activity preference to dark conditions, but this behavior was abolished upon removal of their head, suggesting an extraocular mechanism. In the final section, I demonstrated that stemmata were most sensitive to light in the blue/green part of the visible spectrum. Furthermore, using a chromatic adaptation assay, I showed that stemmata photoreceptors were consistent with having more than one spectrally distinct opsin. While a specific behavioral role for the larval eyes remain inconclusive, the macro- and ultrastructural results suggested the eyes have more sophisticated attributes than a simple light detector. This work has provided the framework upon which specific structure to function questions can be explored to advance our understanding of the Photuris firefly larval visual system.

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