Developmental Variability and Heterochronic Variation in Poeciliid Fishes

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9307245 Strauss Heterochrony, the alteration of timing within ontogeny (development) resulting in accelerated or retarded developmental rates of structures with respect to ancestral conditions, provides an important developmental mechanism for creating morphological diversity among species. This research involves a detailed examination of patterns of morphological and developmental variability in several divergent lineages of poeciliid fishes, a group of livebearing freshwater fishes occurring throughout Middle America. Various aspects of development will be examined including allometric growth gradients (size/shape relationships), absolute and relative growth rates under standardized conditions, and the relative timings of ossification and other discrete ontogenetic events. The overall patterns seen for different species will be interpreted within a phylogenetic framework. %%% The significance of this research is that it will contribute to a more detailed knowledge of the development of poeciliid fishes, and these results can be related to other fish groups. The research also provides valuable information on patterns of morphological change associated with the size and shape of characteristics as well as the timing of development. Finally, this research will utilize this interesting group of fish to develop analytical procedures that can be used to examine growth and development in other organisms. ***