Variation in Culturable Gut Microorganisms of the Catalpa Sphinx Caterpillar (Ceratomia catalpae)

Abstract

Microbial symbionts are important for host organisms, and insects rely on the communities of microorganisms in their guts for several functions. Despite what we are starting to understand of their importance, gut microorganisms have been censused in relatively few insect species. In this study, we examined the types of culturable gut microorganisms in larvae of the catalpa sphinx, Ceratomia catalpae. The gut microbes of this caterpillar are of interest because it feeds only on catalpa trees, and sequesters catalpol from the plant for its own chemical defense. We cultured gut contents of 27 caterpillars from three populations on nutrient agar, and five distinct bacterial colony morphologies were recognized. Four of these morphologies were Gram-negative, and all five were cocci. Future studies with this caterpillar can explore the influence of these bacteria on its ability to feed on catalpa trees and sequester catalpol.