Gut microbes can play key roles in host health. Mollicutes is a class of diverse bacteria whose symbiotic relationships range from beneficial to parasitic in plants, marine life, and insects. The mollicute Entomoplasma corruscae is species-specific to the Winter Firefly Photinus corruscus and putatively functions as a beneficial symbiont. With fireflies holding cultural significance, inferring the effects of symbionts can improve our understanding of firefly survivability. We hypothesized that E. corruscae plays a beneficial role in Winter Firefly health and predict that fireflies harboring high abundance of mollicutes will survive longer and gain more weight over time. In this experiment we separated nearly 200 fireflies into three groups and exposed them to different dietary treatments: antibiotics, mollicute isolates, and control. An E. corruscae strain was grown in the lab and used in the mollicute treatment. After two months, our PCR results indicate that the abundance of mollicutes was drastically reduced through antibiotic ingestion but remained high in fireflies exposed to a mollicute or control diet. Yet, firefly survival and weight did not differ across treatments. In conclusion, E. corruscae may not directly be involved in host survival and may derive greater benefits from the host than it provides in return.
