Patterns and processes of brain diversification within esociform teleosts

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Authors
Means, Sheila M.
Advisor
Lannoo, Michael J.
Issue Date
1995
Keyword
Degree
Thesis (M.S.)
Department
Department of Physiology and Health Science
Other Identifiers
Abstract

The richness of nervous systems represented by extant fishes has not yet been determined; the brain morphology of many species, indeed, many groups, remain undescribed. For this reason we have examined esociform teleosts and focused on three goals: 1) to provide the first basic descriptions of the brains of two esociform teleosts, Esox masquinongy (muskellunge) and Esox lucius (northern pike); 2) to describe the development of E. masquinongy brains; and 3) to compare the neuronal features between E. masquinongy and E. lucius in light of the ontogenic pattern of E. masquinongy. We demonstrate that a suite of differences exists between the brains of these two congeners. Relative to the brains of E. lucius, the brains of E. masquinongy exhibit a number of paedomorphic features. This heterochronic shift parallels the differences in non-neuralmorphological features previously described between these two species. We identify three features that cannot be explained by this heterochronic shift: 1) the optic nerves of E. masquinongy and E. lucius cross oppositely, E. masquinongy have optic nerves that cross left nerve dorsal, E. lucius cross right nerve dorsal; 2) Esox lucius have a consistent cellular discontinuity in the telencephalon between Dm, and Dd that is not present in E. masquinongy; and 3) adult E. lucius retain a neural canal opening that closes in larval E. masquinongy, a peramorphic exception to the paedomorphic pattern.

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