DNA barcoding has become a useful tool in many contexts and has opened up a completely new avenue for taxonomy. DNA barcoding has its widest application in biodiversity and ecological research to detect and describe diversity whenever morphological discrimination is difficult or impossible (e.g., in the case of species lacking diagnostic characters, early life stages, or cryptic species). In this chapter, we outline the utility of including physiological parameters as part of species description in publicly available databases that catalog taxonomic information resulting from barcoding projects. Cryptic species or different life stages of a species often differ in their physiological traits. Thus, if physiological aspects were included in species definitions, the presently cryptic species could be distinguished. We furthermore give suggestions for physiological information that should be included in a species description and describe potential applications of DNA barcoding for research with physiological components.