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Dr. John F. Pilger
Institution(s) / Organization(s):
Agnes Scott College
Society for Integrative and Comparative Biology
My research focuses on the evolutionary developmental biology of two groups of marine protostomes; echiurans (spoon worms) and sipunculans (peanut worms). Both of these animal groups have unsegmented bodies and ambiguous phylogenetic relationships. The aim of my research is to elucidate the phylogenetic position of these two groups within the Lophotrochozoan clade. Undergraduate students are key participants in all aspects of my research; working in the lab year round.
Echiurans share several important developmental and adult characters with the annelids, but the adult echiuran body does not exhibit overt segmentation in the trunk, a trait that has kept them from being classified with the annelids, as traditionally defined. In a recent study, evidence was presented showing an underlying metameric organization of ganglia in the ventral nerve cord of an echiuran. Further, phylogenetic analysis of the DNA sequence from a highly conserved nuclear gene (elongation factor-1 alpha) suggests that the echiurans are derived annelids that have lost their segmentation. Clearly, some phylogenetic ambiguity remains.
Sipunculans also share some similar developmental traits with annelids but they too lack segmentation. In comparison to annelids sipunculans have added a unique larval stage and they possess a significantly modified adult body plan. Thus, morphological evidence alone has not resolved the phylogenetic ambiguity of this group. Sipunculans, to date, have been considered monophyletic, classified within the annelids, or even allied to the mollusks.
My approach to resolving the ambiguous phylogenetic relationships of the echiurans and sipunculans has, until recently, sought to acquire key morphological evidence that could resolve the phylogenetic uncertainty. More recently, however, I have broadened the approach to include molecular data from the development of these animals. In particular, I am asking questions about the development of the axial (anterior to posterior) body plan. The initial data bearing on these questions requires cloning and subsequent identification of Hox and Parahox genes; genes whose products are known to specify the location of morphological features in the body plan. My lab has cloned most of the Hox and Parahox genes from these animals. As we complete this phase of the work we will next determine the spatial and temporal deployment of the genes during development, looking for correlations between deployment patterns and the development of significant morphological features. These data will lead to key hypotheses about the functional roles of these genes in development. Testing these hypotheses will involve experiments that manipulate the gene activity through silencing (e.g. morpholinos or RNAi) and ectopic expression. Ultimately, the results of these experiments will allow me to compare the development of the body plan in these organisms with similar data from putative phylogenetic allies, to infer phylogenetic relationships and to propose possible evolutionary scenarios that led to these organisms.
More broadly I am also interested in the biology, ecology and biogeography of echiurans. In that context I edit the echiuran section of the WoRMS database and participate in systematic and biogeographic efforts worldwide.
Ph.D., Biology, University of Southern California, Los Angeles, California, U.S.A.
B.S., Biological Sciences, University of Southern California, Los Angeles, California, U.S.A.
Area of Expertise / Interest:
Evolutionary developmental biology; Ecology; Systematics
Preferred Language: English
Home Page URL: http://biology.agnesscott.edu/sub-pages/pilger.htm
Links to Projects or Publications:
Gulf of Mexico Origin, Waters, and Biota: Biodiversity
Keywords: Taxonomy, Echiura, Sipuncula, development
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