College of Science and Health Theses and Dissertations

Date of Award

Summer 8-21-2022

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Biological Science

First Advisor

Windsor Aguirre, PhD

Second Advisor

Elizabeth LeClair, PhD

Third Advisor

Jalene LaMontagne, PhD

Abstract

Humans are causing large-scale changes in environmental conditions across the planet including in temperature. Changes in the environmental conditions can lead to phenotypic changes in ectotherms that affect adaptively important traits like body shape and the axial skeleton. Previous studies have shown that temperature changes during development significantly affects body shape and vertebral number in the Mexican tetra Astyanax mexicanus. How these changes arise early in development is not clear. In this study, I examine how changes in developmental temperature affect body shape in larval and juvenile fish, the order of ossification of elements of the axial skeleton, the size of set bone ossification, and the variation in size of set ossification of different skeletal structures. Fertilized eggs from laboratory reared A. mexicanus were maintained at 20°C, 24°C, and 28°C, then collected, preserved, imaged, cleared, and stained with alizarin red to examine bone ossification. Temperature significantly influenced the body shape of larval A. mexicanus, resulting in fish in the 28°C water treatment having deeper bodies compared to fish reared at 20°C. There was not a significant relationship between temperature and the order of bone ossification, indicating that bone developmental order is constrained across the range of developmental temperatures examined. However, temperature significantly affected the size of ossification of certain skeletal structures with the bones of fish reared at 20°C ossifying at larger sizes than fish reared at 24°C and 28°C. There was also a relationship between temperature and the variation in set size of bone ossification among crosses. Fish developing at 20°C tended to exhibit the most variability in the size of set ossification among crosses. This study examens whether different rearing temperatures can affect the early stages of larval development thus resulting in modified phenotypes of adult A. mexicanus. My research 6 also provides a baseline for future studies examining phenotypic plasticity in body shape and skeletal ossification in fish colonizing new habitats or fish in rapidly changing environments.

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