A multifaceted analysis of Semaphorin-induced neuroplasticity in the nervous system of Gryllus bimaculatus

Author

Ean Lev Small, Bowdoin CollegeFollow

Year of Graduation

2023

Level of Access

Restricted Access Thesis

Embargo Period

5-18-2023

Department or Program

Biology

First Advisor

Hadley Horch

Abstract

The auditory system of the Mediterranean cricket, Gryllus bimaculatus, is an optimal model for neuroplasticity. Following unilateral deafferentation, the Ascending Auditory Neurons 1 and 2 (AN-1 and AN-2) sprout across the previously respected prothoracic ganglion midline, forming connections with contralateral auditory afferents. Class 1 Semaphorin transcript, sema1a.2, encodes chemotropins that guide auditory axons during development. Deafferentation causes the significant downregulation of sema1a.2 18 hours post-injury. The present study investigated the following two biological questions: 1. Whether a knockdown in the levels of Sema1a.2 affects crickets’ behavioral and physiological response to predatorial sound stimuli; and 2. Whether particular physiological outputs correlate to specific behavioral responses and whether those characteristic physiological outputs can predict behavior. Here, we injected 7^th instar larval stage crickets with double-stranded RNA targeted to knockdown sema1a.2. Following injection, crickets were isolated until reaching adulthood, where they were then flown and presented with predatorial bat ultrasound. A sufficiently trained DeepLabCut neural network was used to analyze cricket behavior. The results were computed by a modified R pipeline to visualize and quantify cricket movement. Once flown, physiological recordings of cricket auditory neuronal responses were obtained in response to the same sound stimulus presented during behavioral experimentation. While this study did not find any statistically significant results, there was an observable difference in the turn angle and physiological output between sema1a.2 KDs and GFP control crickets. An increase in sample size in the future will further elucidate the impact of Sema1a.2 on the maintenance and plasticity of the cricket auditory system.