SICB2015: The Role of Myoblast Fusion in the Evolution of Muscle Fiber Size in Anolis lizards

Jake Stercula of the Johnson Lab and his 2015 SICB poster

Muscle fiber size can vary based on the frequency of use, or due to the fusion of multiple mononucleated myoblasts during development to form multinucleated fibers. To test if variation in muscle fiber size was due to frequent use or due to differences in development between species, Jacob Stercula of the Johnson lab examined the fiber size and number of nuclei for the ceratohyoid and the retractor penis magnus (RPM) of nine species of anoles. Most species exhibit a positive relationship between fiber size and the number of nuclei in both muscle types. Among species, this positive relationship between fiber size and the number of nuclei exists in the RPM muscle when accounting for phylogeny using independent contrasts, whereas the ceratohyoid shows a positive trend, though the relationship was not significant. This suggests that for the RPM, muscle fiber size is evolutionarily conserved and is due to differences in development among species rather than differences in the amount of use. The size of the ceratohyoid muscle however, maybe be influenced by both the frequency of use and the fusion of myoblasts during development.