DISSERTATION RESEARCH: Gastropod shells: A window into the developmental origins of diversity

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This project investigates how different types of shell shapes are encoded in snail embryos. Animal form is marvelously varied. This study addresses the question: what are the developmental mechanisms that produce such diversity? Snails have long been a model system for studying biological form. They have diverse shapes but are easy to measure due to their mathematically regular coiling and have been a major study group since Charles Darwin's famous voyage around the world. Darwin's approach to the study of animal form included investigations of patterns of change in the snail-rich fossil record (paleontology). Modern developmental biology uses molecular tools to understand how genes determine snail form. This project will determine the genetic and environmental interactions that may underlie a conspicuous pattern in paleontology, the repeated evolution of non-coiled shells from coiled ancestors. The researchers will combine computer imaging technology, genetic manipulation and paleontology to provide unparalleled precision in determining how both genes and their environment shape an organism through time. Broader societal impacts will result from this work due in part to the design and implementation of a workshop on visual literacy. This workshop will improve the ability of the researchers and the scientific community to understand and convey complex visual information to the public. The workshop materials will be posted online for increased access. This project investigates the developmental basis of snail shell morphology and the transition from coiled to non-coiled shells in the emerging model system, the Common Slipper Shell (Crepidula fornicata). Specifically, it evaluates the hypothesis that simple modification in signaling patterns in a protein named decapentaplegic could be the basis for a pattern of non-coiled shell evolution. Other shell developmental genes also will be evaluated for the ability to affect shell patterning more generally. Genetic pathways influenced by changes in shell coiling will be manipulated in developing animals to isolate their individual effects on morphology. Detailed morphological data is required for this work. Scanning electron microscopy will be used to visualize the process of torsion and to assess morphological changes across the entire embryo in response to genetic perturbations. Computed tomography (CT scanning) will enable the use of 3-dimensional shape analysis of embryo and shell form with enhanced precision. The use of these computer-assisted technologies combined with molecular techniques will allow new insight into how paleontological patterns are formed.