Graduation Date

Spring 2023

Document Type

Thesis

Program

Master of Science degree with a major in Biology

Committee Chair Name

Allison Bronson

Committee Chair Affiliation

HSU Faculty or Staff

Second Committee Member Name

John Reiss

Second Committee Member Affiliation

HSU Faculty or Staff

Third Committee Member Name

Karen Kiemnec-Tyburczy

Third Committee Member Affiliation

HSU Faculty or Staff

Fourth Committee Member Name

Ethan Gahtan

Subject Categories

Biology

Abstract

Neural crest cells (NCCs) and mesodermal somites independently produce embryonic mesenchyme as a precursor to the chondrocytes and osteocytes of the vertebrate skeleton. In mammals and teleosts, NCCs only contribute to the dermal cranial skeleton, while the mesodermal somites and lateral plate mesoderm form the entire dermal and endochondral postcranial skeleton. In sharks, NCCs contribute to both the cranial and trunk integumentary skeleton. This suggests that contribution of the trunk neural crest mesenchyme to the integumentary skeleton was an ancestral condition for all vertebrates that was lost over evolutionary time in the osteichthyan lineage, but the evolutionary timing of this loss is unclear. This study documents trunk neural crest cell delamination and migration from the neural crest and investigates the developmental origin of the dermal bony scutes in White Sturgeon (Acipenser transmontanus). I find that putative trunk neural crest cells emigrate from the neural crest before neural tube closure. This is the first described evidence among vertebrates of this timing of trunk neural crest cell emigration. I also provide evidence that the bony scutes of White Sturgeon may at least partially develop from the neural crest. This suggests that contribution of trunk neural crest ectomesenchyme to the exoskeleton was a vertebrate ancestral condition that was preserved in early-diverging lineages of bony fishes, and convergently lost in teleosts and tetrapods.

Citation Style

Harvard

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