Comparing and Informing Morphological Species Identifications and Boundaries in Arthropod Gut-dwelling Protists Using Molecular Phylogenetic Analyses

Trichomycetes are fungal and protistan symbionts of arthropods and have been found in marine, freshwater, and terrestrial habitats on every continent except Antarctica. Minimally, trichomycetes associate commensally with their immature aquatic hosts (including black flies, mayflies, stoneflies, isopods, and others) attaching to the chitinous lining of the mid or hindgut. Classified with trichomycetes are Paramoebidium, a group of protists which associate in an obligate manner with their hosts. To date, 16 species of Paramoebidium have been identified by morphological approaches. These descriptions have included characterization and discrimination of species based on thallus (body) length and width, differences in the holdfast (structure used to attach to the gut of the host), and the appearance of the asexual, motile amoebae they release. Several challenges arise from this method. Namely, Paramoebidium species can be unremarkable in appearance. Immature Paramoebidium can have large variation, and finding a specimen in the process of releasing amoebae is very difficult as live organisms must be dissected directly from host tissue. We have been using molecular and phylogenetic approaches (sequencing rDNA genes) to assess morpho-species boundaries and their potential to differentiate and infer evolutionary relationships among Paramoebidium species. To date, efforts to compare recent molecular findings to morphological data have not been done. We plan to perform a morphological comparison of specimens used in the molecular data to highlight the pros and cons of the current classification system for Paramoebidium.