A symbiosis between Euploea butterflies and yeasts

Euploea butterflies harbor many yeast species on their mouthparts, legs, and wings. In this study, we focused on the distribution of two dominant yeast species, Candida corydali and Metschnikowia koreensis . We investigated (1) where the two species present on/in the body of butterfly; (2) if they colonized and grow in the butterfly; and (3) whether the butterflies carry these two yeasts because of their flower-visiting behaviors. Results show that C. corydali was isolated from the digestive tracts of 89% butterflies, whereas M. koreensis was isolated from the digestive tracts of 94% butterflies. Both of two species were more frequently isolated from the digestive tracts than other parts of the butterflies. We also found that high population of M. koreensis (5.0 × 10 2 to 1.4 × 10 4 CFU per tract) and C. corydali (1.8 × 10 3 CFU per tract) from digestive tracts. This suggested that C. corydali and M. koreensis present in the gut are not just food contaminants, they might colonize the gut of Euploea butterflies. The fluctuation of yeast isolation rates shows that higher frequencies of yeast occurrence were synchronized with local flower seasons. These data suggested that presence of yeasts in the gastrointestinal tracts correlated with the feeding and migration behavior of the winter migrating butterflies, Euploea spp.