Phylogeny of the Metastrongyloid Nematodes: Inferring Patterns of Infection Site and Life Cycle Evolution Among 'Lungworms'

Ohio Wesleyan University, Delaware OH

Investigators

Abstract

A grant has been awarded to Dr. Ramon Carreno of Ohio Wesleyan University and Dr. Steven Nadler at the University of California, Davis to to study the phylogeny of the Metastrongyloid Nematodes. Nematode parasites occurring in the respiratory tracts of mammals and known collectively as "lungworms" include many species that can be highly pathogenic to their hosts. These nematodes show a wide range of variation in morphological features and life history strategies, and some have established infection sites in their mammalian hosts that are outside of the respiratory tract. The main objective of this research is to use DNA sequence data to reconstruct the genealogical (phylogenetic) relationships of lungworms in the nematode superfamily Metastrongyloidea, and to use this genealogy to understand the history of changes in life cycles, morphology, and infection site specificity among members of this group. Results from DNA sequence data will be complemented by an independent genealogical analysis of morphological features from museum and field-collected specimens. In addition to understanding patterns of change in life cycles and tissue/organ specificity, the origins of a perplexing group, lungworms parasitizing marine mammals, will also be determined from phylogenetic analyses. For example, the origin of a group of lungworms that are found almost exclusively in toothed whales has been widely disputed. Likewise, some species that parasitize seals and sea lions have striking morphological similarities to those infecting terrestrial carnivores. Although many different views on the evolutionary history of the Metastrongyloidea have been proposed during the last 50 years, there have been no attempts to estimate their phylogeny using modern analytical methods. This research will provide a foundation of knowledge for understanding patterns of evolution among these nematode parasites, and will provide an historical framework for the taxonomy of this superfamily. This investigation will include scientific training opportunities in parasitology and molecular biology for undergraduate and graduate students , and research outcomes will lead to increased understanding of the biology of parasitism in nematodes.