RUI-Collaborative Research: Developmental Bases of Body Plan Diversity within the Phylum Cnidaria--A Comparison of Polyp and Medusa Development

Pomona College, Claremont CA

Investigators

Abstract

Martinez 0316519 Data from taxa which arose early within the Metazoa are critical for understanding the origin and early evolution of animal developmental processes. The phylum Cnidaria is notable not only for its basal position within the Metazoa, but also for having life cycle stages with strikingly different organizations. In many cnidarian species, the sessile polyp stage is followed by formation of the morphologically very different free-swimming medusa stage. While the developmental biology of the polyp stage has received a substantial amount of attention, less is known about the development of the medusa stage. The relative lack of information about medusa development is unfortunate in part because sensory organs are present almost exclusively in the medusa stage, with eyes present only in medusae. To make clear the full implications of cnidarian development for early animal evolution, the similarities and differences between polyp and medusa development should be characterized. In addition, the phylum provides an unusual opportunity to study the bases of major differences in body organization without the need to compare organisms from distantly related taxonomic groups. The proposed research will take advantage of information on polyp development to address questions about developmental differences between the polyp and medusa stages. One hypothesis to be tested is that early development of the oral end of the polyp and the medusa is similar but that specification of the aboral end differs. Expression of selected genes will be compared in developing polyps and medusae of Podocoryna carnea. Genes to be examined include members of the Wnt, Emx, FoxA, and NK-2 families. Developing medusae will be treated with reagents targeting specific signaling pathways. Grafting will be used to determine developmental properties of specific regions of the developing medusa. A strength of the project is the benefits it offers the undergraduate students involved. These relate in part to the fact that proposed research involves a collaboration of two PIs at undergraduate institutions. During the summers, the two PIs and undergraduates from both colleges will work together as a single research group. This arrangement will give students the intellectual excitement of working in a relatively large, focused research group. A second benefit of this work for undergraduate research students is that it illustrates the overlap between diverse areas of biology, including developmental biology, evolutionary biology, systematics, and invertebrate zoology.