Colonial Animals: One Genetic Individual and Many Bodies
2013 REU Project:
This project will employ collections of Bryozoa, the only wholly colonial phylum of animals, to address a fundamental biological question – how does evolution act to create new body plans? In bryozoans, sexually produced larvae with one body plan are released by a colony, settle, and undergo metamorphosis. From these larvae, asexually budded zooids together comprise the body of a single genetic individual, the colony. In many species, zooids are amazingly different morphologically (polymorphic), even though they are identical genetically. This life cycle and its polymorphism, in turn, can be seen as a laboratory to help discover how different body plans have come into being.
One part of studying this system involves microscopic imaging of zooid life stages—alive in their aqueous environment, using conventional histological techniques, and using scanning electron microscopy. The plan is to compare larval, zooid, and colony development in a few select species, some with and others without polymorphs, representing the phylogenetic breadth of the phylum. Molecular genetic and developmental protocols can now be used to compare gene regulation and patterning in feeding zooids and polymorphic zooids of colonies, as well as in earlier embryonic and larval stages. Principal goals are to relate a modern understanding of development to current bryozoan evolutionary biology and systematics; and to the broad contexts of development and diverse body plans among metazoans. This larger project, in collaboration with evolutionary developmental biologist Chris Lowe at Stanford University, is already underway with work on a highly derived polymorphic species. The summer internship will concentrate on a second, much "simpler" species representing freshwater bryozoans (Phylactolaemata, the most evolutionarily primitive group in the phylum) to begin erecting a evolutionary frame for anatomical and gene expression comparisons of the morphological genesis of genetically identical but morphologically diverse embryonic, larval, metamorphosing, and asexually budding life history stages.
Research methods and techniques: High-resolution digital images and cinematography of live freshwater bryozoan colonies (Phylactolaemata, the most evolutionarily primitive group in the phylum) will be used in the lab to document larval fission and release from the colony, settlement, metamorphosis, and zooid asexual budding. Specimens representing these different life history stages will be prepared, then analyzed using histological and SEM techniques. If time permits, the intern will assist with the use of a filter-based protocol to isolate total RNA from tissue samples of these different life stages. This is the first step in preparation of a cDNA library from which orthologs of regulatory genes can be recognized, and primers for visualization of gene expression can be constructed.
Curator/Advisor: Dr. Scott Lidgard (Associate Curator, Geology)