Visual Head Reflexes Underlying Prey Interception in Dragonflies

Date of Award

6-2020

Document Type

Union College Only

Degree Name

Bachelor of Science

Department

Biology

First Advisor

Robert Olberg, Ph.D.

Keywords

Dragonflies, TSDNs, visual neurons, dragonfly head movements

Abstract

Dragonflies are small, yet mighty, insects that are able to tell us a lot about their neural components from their movements. In this thesis, I studied dragonfly head movements in response to a simulated prey object in order to compare these movements with those elicited by individual feature-detecting visual neurons, called Target-Selective Descending Neurons (TSDNs). My hypothesis is that this small cluster of neurons is able to steer the dragonfly’s flight during prey interception. While in flight, these neurons elicit precise turning adjustments of the wings and head. My goal was to determine whether the visually induced head action in Aeshnid dragonflies can be predicted from our knowledge of the movements produced by individual neurons. The moving targets were moved either vertically or horizontally (up, down, left, and right) at two different speeds. The dragonflies' head reactions to the stimuli were recorded at 240 frames per second. The video was later digitized and analyzed to determine the movements of the head in response to the target crossing the screen. Our results show that there were some inconsistencies with the reactions, however there was a common occurrence of head nods in all responses. We predict that these movements are a form of tracking that the animals elicit, before determining if the prey is worthy or not to be captured.

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