A phylogenetic evaluation of the nematode ventral nerve cord

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.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Crop Sciences

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2022

Author dc:creator

• Lanzatella, Marissa

Contributors dc:contributor

• Schroeder, Nathan E
• Gillette, Rhanor
• Vidal-Gadea, Andres
• Ugarte, Carmen

• nematode phylogeny
• ventral nerve cord
• nervous system development
• nervous system evolution

Statement dc:rights

• Copyright 2021 Marissa Lanzatella

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/113088

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F113088