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Mon February 13, 2012
Dr. Bard Ermentrout, University of Pittsburgh - Evolution of Colorful Shells
a – In today's Academic Minute, Dr. Bard Ermentrout of the University of Pittsburgh explains what the colorful patterns on a seashell can reveal about the evolutionary history of the creature that created it.
Bard Ermentrout is a professor of mathematics and the University Professor of Computational Biology at the University of Pittsburgh. His research program examines models of neural and muscle physiology and is focused on the area of mathematical neuroscience that seeks to understand patterns of activity in networks of neurons. He holds a Ph.D. from the University of Chicago.
Dr. Bard Ermentrout - Evolution of Colorful Shells
I have always been interested in how biological systems create complex spatial and time-varying patterns such as animal coats, fingerprints, and visual hallucinations. Among the most beautiful are the pigmentations of seashells, and in particular, the cone shells.
In previous work, my collaborators and I have developed a computer model for these patterns that is based on feedback between the pigmentation pattern that has already been laid down on the shell and the neural activity that controls the secretion of new pigment. Our model has about a dozen parameters which correspond directly to physiological and anatomical parameters in the nervous system.
By tuning the parameters, we were able to mimic the patterns on 19 species of cones. Other biologists had already used the DNA of these animals to create an evolutionary tree showing how currently living shells evolved from their ancestors. We used a similar method to create a tree based only on the parameters of our neural model. To our surprise, we found that the neural-based tree and the DNA-based tree were very similar. Thus we were able to use our model to infer what ancestral cone shells would look like something that is impossible using the DNA tree.
It turns out that, using ultraviolet light, it is now possible image the patterns on fossil shells. This will enable us to compare our predictions with actual fossils.
Changes in the parameters in our model are directly related to the structure of the animals nervous system, so, for the first time, we will also be able to follow the evolution of the nervous system. In the future, we will use our neurally based model to study the amazing camouflage patterns on the cephalopods such as the squid, octopus, and cuttlefish.