Date of Award


Degree Type


Degree Name

Master of Science (MS)




Developmental morphology of the axial skeleton of Esox lucius (i.e., northern pike and type species) and E. masquinongy (i.e., muskellunge) was investigated. More than 1,000 specimens were examined ranging in size from approximately 10 mm notochordal length (NL) post-hatching juveniles to over 80 mm standard length (SL) foraging sub-adults. Results show that regardless of individual variation, the relative sequence of bone formation and mineralization is consistent between the two species. This consistent developmental pattern enabled construction of an ontogenetic staging scheme of eight developmental stages, each characterized by one defining criterion. The first appearance in cartilage and/or first sign of mineralization of each axial skeleton bone was plotted against time and age for each species and compared. Observed variation in bone development (e.g., number of epurals) inconsistent with the published literature is discussed. Based on the entire developmental study, Esox lucius grows in size faster than E. masquinongy, but its axial skeleton develops and mineralizes slower. For example, at 25 mm SL, the axial skeleton of E. masquinongy is 55% mineralized, while E. lucius is only 25% mineralized. Esox masquinongy at this point however, is 1000 hrs old, while E. lucius is only 700 hrs. These results suggest that E. masquinongy has adapted a developmental strategy whereby more energy is put into skeletal development than growth in size. This strategy may reflect E. masquinongy's early foraging behavior. Unlike E. lucius, E. masquinongy absorbs its yolk sac earlier in life, and becomes an active predator just a few days after hatching. A well mineralized axial skeleton with developed dentition would facilitate this early predacious behavior.

Creative Commons License

Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License.