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Title:A phylogenetic evaluation of the nematode ventral nerve cord
Author(s):Lanzatella, Marissa
Advisor(s):Schroeder, Nathan E
Contributor(s):Gillette, Rhanor; Vidal-Gadea, Andres; Ugarte, Carmen
Department / Program:Crop Sciences
Discipline:Crop Sciences
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):nematode phylogeny
ventral nerve cord
nervous system development
nervous system evolution
Abstract:Nervous systems are incredibly complex networks that, in order to understand, we rely on models like Caenorhabditis elegans to deconstruct. Due to the prevalence of C. elegans and other derived nematode research, it was long assumed that nematode nervous systems were highly conserved across the phylum. Previous evidence revealed that within the derived clades, the assumption of conservation was wrong and that the timing of neuronal development varied. As these previous accountings disregarded the basal clades except for some sporadic observations, this research endeavored to corroborate that the nervous systems of basal nematodes are in fact the most complex and there is a nervous system simplification from the basal to the derived clades. My findings did indeed reveal a simplification of the nerve cord, specifically there appears to be a decrease in ventral nerve cord neurons between the basal and derived clades, which adds further evidence that class Enoplea bears most similarity to the nematode ancestor. A potential reason for nervous system simplification could lie in marine pressures as large marine nematodes are adapted to move through sediment and have more neurons in their ventral nerve cords while smaller marine worms can navigate the water column and were observed to have less neurons, though this hypothesis needs to be more thoroughly investigated. In addition, ventral nerve cord development within Mononchidae appears to be consistent with derived clades and despite basal clade indeterminate development, Mononchidae nervous systems are invariant as adults. Considering all instances of recorded ventral nerve cord development, it appears the precise timing of development shifts but there is always a moment of rapid neurogenesis, often preceding a molt, like what was observed within Mononchidae. These results indicate that while nematode nervous systems may vary in their cell numbers and timing, their general organization and development is highly conserved as previously suggested.
Issue Date:2021-07-22
Rights Information:Copyright 2021 Marissa Lanzatella
Date Available in IDEALS:2022-01-12
Date Deposited:2021-08

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