Euglenids are a diverse group of free-living flagellates found in marine, brackish, and freshwater environments, some of which are indicator species for environmental pollution. Members of the group have diverse modes of nutrition, including bacteriotrophy (capable of eating bacteria), eukaryotrophy (the ability to engulf large prey such as other eukaryotes), phototrophy (possess photosynthetic plastids), and osmotrophy (lack a feeding apparatus and photosynthesis, absorb organic molecules). The objectives of our research on euglenids are (a) to document evolutionary trends in characters associated with their pellicle, photoreception apparatus, and feeding apparatus, (b) to understand the adaptive relationship between pellicle diversity and the secondary origin of chloroplasts, and (c) to develop an accurate taxonomic framework for interpreting euglenid phylogeny. Much of this work has focused on the diversity of pellicle strips, which are long proteinaceous structures that articulate along their lateral margins and subtend the plasma membrane. The characteristics of different pellicles are intimately associated with the four different modes of nutrition listed above.