College of Science and Health Theses and Dissertations

Date of Award

Fall 11-26-2019

Degree Type


Degree Name

Master of Science (MS)


Biological Science

First Advisor

Windsor Aguirre, PhD

Second Advisor

Margaret Bell, PhD

Third Advisor

Jason Bystriansky, PhD


Environmental fluctuations can change the phenotypic traits of ectotherms. Ectotherms such as fishes are very susceptible to changes in temperature. Recent studies on adults of the Mexican tetra, Astyanax mexicanus, indicate that variation in temperature during development significantly impacts vertebral number and body shape. Since vertebral number and somite number are related, I examined whether temperature significantly impacts somitogenesis and the early development of the body axis in this species. Fertilized eggs of the surface form of lab-reared Astyanax mexicanus were subjected to temperature treatments of 20°C, 24°C, and 28°C, and fixed hourly as they developed until they hatched. Embryos were stained with DAPI and imaged using a confocal microsope. Body length, somite number, unsegmented tail length, and somite length were measured. Temperature significantly influenced the general rate of somitogenesis and all phenotypic traits measured. Surprisingly, temperature significantly influenced the unsegmented tail length even when variation in general developmental rate was accounted for, such that embryos reared at 24°C had a significantly longer unsegmented tail length than embryos reared at 20°C and 28°C. Although somite length was variable between developmental stages and along the body axis, temperature also seemed to influence somite length. For example, embryos reared at 28°C had consistently shorter posterior somites at the 40 somite stage of development than embryos reared at 20°C or 24°C. Understanding whether these temperature effects on somitogenesis also influence the phenotypic properties of adults is a major avenue of future research.This study provides a better understanding of how temperature influences the early stages of the development of the body axis in this emerging model species. It will also provide a baseline for future studies examining the influence of phenotypic plasticity on body form variation in characids colonizing new habitats.

SLP Collection


Included in

Biology Commons