Department of Biology

Program

Evolution, Ecology & Behavior

Research Areas

• Developmental Mechanisms and Regulation in Eukaryotic Systems
• Evolution

Education

Ph.D., Duke University, 1967
Postdoctoral Fellow: National Naval Medical Center, 1967-69; MIT, 1969-71

Awards

Director, Indiana Molecular Biology Institute
Editor in Chief, Evolution & Development

Guggenheim Fellow
Fellow of the American Academy of Arts and Sciences
Alexander Kowalevsky Medal, St. Petersburg Society of Naturalists
Daniel Giraud Elliot Medal, National Academy of Sciences USA
Sewall Wright Award, American Society of Naturalists

Research Description

Evolutionary developmental biology is the study of how developmental processes influence the course of evolution.  The link lies in the fact that body form evolves over long time periods, but morphology arises each generation in the development of an individual.  In a collaborative effort with Beth Raff, we study several aspects of this problem at the level of embryonic and larval development.  Our research focuses on a pair of closely related Australian sea urchins that allow us to compare the evolution of developmental mechanisms of two closely related species with dramatically different modes of development.  Part of the work is done in the School of Biological Sciences at the University of Sydney (http://www.bio.usyd.edu.au/).

Evolution of early development
The primitive mode of development for sea urchins is via a feeding larva called a pluteus.  This larva has arms used in feeding.  After a period of a few weeks of feeding, a tiny sea urchin grows within, and is released by metamorphosis.  One of our species, Heliocidaris tuberculata develops in this way.  Its sister species, H. erythrogramma, has omitted the feeding larva and within 3 - 4 days produces a tiny sea urchin through direct development.  We are studying the evolution of regulatory changes that underlie this radical shift in development.  Studies of regulators of axial development have allowed us to understand how some of the dramatic change in larval shape has evolved.  The use of cross species hybrids between these species and genomic methods is revealing how timing of developmental events has become reorganized.

Larval origins
The earliest animals evidently developed directly.  Thus the elaborate larvae of marine animals with their body plans distinct from those of their adults did not arise until after the great radiation of animals was well under way.  We have been studying distinctly larval structures to document gene co-option in the evolution of larvae.  We have also been trying to reconstruct the evolutionary intermediates through which feeding larvae evolve into non-feeding, direct developing forms.  A developmental intermediate represented by a facultative-feeding sea urchin from Panama has been crucial to understanding early selective steps in the process.

How embryos fossilize
Marine embryos would seem unlikely to have left fossils.  However, surprising and well preserved fossil embryos occur in late Precambrian and Cambrian phosphorites.  These give insights into the originis of marine larvae and life histories.  We are collaborating with other investigators in establishing mechanisms of embryo decay and preservation using large Australian sea urchin embryos as analogs of early embryos.  We have established the major finding that the blocking of autolysis is a critical step in the process.  Current studies are examining the roles of bacteria in fossilization.

Select Publications

Love, A., Lee, A., and Raff, R. A. 2008. Evolutionary patterns of gene expression in the sea urchin larval gut: Co-option and dissociation in larval origins and evolution. Evo. Dev. 10: (In press).

Smith, M. S., Zigler, K. E., and Raff, R. A. 2007. Evolution of direct developing larvae: Selection vs. loss. BioEssays, 29: 566-571.

Raff, R. A. 2007. Written in stone: Fossils, genes and evo-devo.  Nature Rev. Genet. 8: 911-920.

Love, A., Andrews, M., and Raff, R. A. 2007. Pluteus larval arm morphogenesis and evolution: Gene expression patterns in a novel animal appendage and their transformation in the origin of direct development. Evo. Dev. 9: 51-68.

Raff, R. A. 2007. Origins of the Other Metazoan Body Plans: The Evolution of Larval Forms. Phil Trans Roy Soc. B. In press.

Hagadorn, J. W., Xiao, S., Donoghue,P. C. J.,  Bengtson, S., Gostling, N. J., Pawlowska, M., Raff, E. C.,  Raff, R. A. , Turner, F. R., Chongyu, Y., Zhou, C., Yuan, X., McFeely, M. B., Stampanoni, M., Nealson. K. H. 2006. Cellular and Subcellular Structures of Neoproterozoic Animal Embryos. Science 314: 291-294.

Love, A. and Raff, R. A. 2006. Larval ectoderm, organizational homology, and the origins of evolutionary novelty. J Exp Zoolog B Mol Dev Evol. 306:18-34.

Raff, E. C., Villinski, J. A., Turner, F. R., Donahue, P. C., and Raff, R. A. 2006. Experimental taphonomy: feasibility of fossil embryos. Proc Natl Acad Sci U S A. 103(15):5846-5851.

Raff, R. A. 2005. Stand up for evolution. Evo. Dev. 7:273-275.

Raff, R.A. 1996.  The Shape of Life:  Genes, Development and the Evolution of Animal Form.  University of Chicago Press.