PEET: Lower Worms Of The Meiofauna - Models for Early Metazoan Evolution

University Of Maine, Orono ME

Investigators

Abstract

Abstract Among the small invertebrates living between sand grains in the marine environment, are tiny, cryptic worms that many consider to be the most primitive of all bilaterally symmetrical animals (that is, all animals excluding the cnidarians and sponges). These worms include two small groups called acoel and catenulid turbellarians which are now classified in the phylum Platyhelminthes (flatworms) but that, according to some systematists, may not even be related to the more familiar flatworms such as planarians and polyclads. Another of these primitive worm groups is the Gnathostomulida, whose relationships to other phyla of invertebrates have been similarly controversial; by some theories, gnathostomulids are like the ancestors of the flatworms. S. Tyler and W. Sterrer, who have long studied these worms, propose training new students in how to find and handle them and in how to decipher systematic relationships. Students working in S. Tyler's laboratory at the University of Maine will concentrate on microscopical techniques and taxonomy of flatworm groups. New characters discerned through applying fluorescence and electron microscopy on these animals show that the relationships among them are not well represented by the current classification system. Students working with Sterrer in his laboratory in Bermuda and accompanying him on sampling trips will gauge patterns of distribution of flatworms and gnathostomulids and gather specimens for the microscopical and molecular studies. He will also train students in curatorial techniques. The major focus of this project is the training of students-to give them the tools to discover and describe the many species of these difficult-to-find, yet remarkably abundant, enigmatic animals and to make sense of their diversity. Without new researchers being trained to identify these cryptic animals, we will lose the expertise needed to address important questions of animal origins. The knowledge these students unearth will likely provide critical clues to resolve far-reaching questions of how the major groups of animals are related. Identifying and characterizing the many undescribed species of lower flatworms will provide a better understanding of their biodiversity; knowledge of the geographic distribution of both these flatworms and gnathostomulids should provide a means for seeing where they arose and how they diversified and spread around the Earth. The results of these students' research will be displayed on a Web site so that anyone with a Web browser can use that data to identify similar worms they might find or to gauge the historical relationships of geographic sites.