Dissertation Research: Osteological Size and Shape Variation and the Evolution of Ossification Sequence in Ostariophysan Fishes

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0073267Chernoff and ThomasCurrent studies of the morphology of organisms emphasize the idea that changes in developmental processes are fundamental to differences in the shape, size, and form of related species. A relatively simple shift in the timing of a developmental event can potentially result in striking morphological divergence between two related lineages. This project, by graduate student Katherine Thomas under the direction of Dr. Barry Chernoff, seeks to investigate the relationship between developmental timing and morphological change by comparing skeletal development in four lineages of freshwater fishes. The fish skeleton is composed of numerous spatially and functionally related bony elements, and an important event in the growth of each element is the time at which the bone begins to ossify (or take up calcium salts). Thus, changes in the timing of ossification events may strongly influence adult morphology. This study will document patterns of skeletal development in four fish species representing the major lineages within the superorder Ostariophysi, an assemblage of primarily freshwater fishes including catfishes, tetras, and their relatives. The developmental times at which bones ossify will be recorded, and this information will be used to address the following three questions. 1) How variable is the relative timing of bone ossification among related species? 2) Do any sets of bones appear to be highly correlated among species in the time at which they ossify, suggesting strong functional or developmental associations among the elements of the set? 3) Is there a relationship between the developmental time at which a bone ossifies and its variation in size and shape? Answering these questions will strengthen our knowledge of how changes in developmental patterns and processes mediate morphological diversification.