9318249 BALDWIN The objective of the proposed research is to understand how the feeding structures of soil nematodes have adapted with time to include diversity from microbivorism (primarily feeding on beneficial bacteria) to varying types of parasitism. These diverse feeding adaptations have important ecological (e.g. bacterial feeders), agricultural (e.g. plant and animal parasites) implications. Presently, different feeding strategies are understood in terms of crude overall structure of the buccal capsule (mouth region), but there is little or no explanation of phylogenetic relationships among the various feeding types. Understanding the phylogeny of diverse feeding structures requires the resolution of conflicts about their structure. These conflicts can be resolved by building upon the detailed morphological and developmental knowledge in the model (bacterial-feeding) nematode, Caenorhabditis elegans, and extending this model to close microbivorous relatives (Rhabditida) as well as more distant parasitic relatives. Comparative detailed morphology/development will be primarily accomplished using transmission electron microscopy. Phylogenetic relationships of morphological/developmental characters of buccal capsules in a range of nematodes will be interpreted in light of a parallel set of data from DNA sequences from the same nematodes. Since sequences from subunits of RNA polymerase II seem to be particularly informative, they will be used to develop an independent molecular-based genealogical tree. This tree will be used to infer the simplest explanation for the pattern and direction of change of buccal capsule feeding structures and associated feeding adaptations. %%% Soil dwelling nematode worms are an important, unseen part of virtually all ecosystems. They can be economically important as parasitic pests of plants and consumers of beneficial bacteria or, alternatively, these same feeding strategies can be beneficial if directed against pest organisms such as weeds and ins ect pests. This project will investigate relationships among a variety of nematode species by utilizing both information from detailed studies of the ultrastructure of the mouth parts and feeding apparatus and from molecular sequencing of portions of the RNA polymerase II gene. ***
