Effect of symbiotic bee fungus on survival of stingless bee Heterotrigona itama larvae

Abstract

Aims: Symbiotic bee fungus associated with the stingless bee larval food has been revealed to play a major role in performing a mutual relationship with the host. The fungus is believed capable to produce crucial nutrients that are required for larval pupation. However, detailed information on the fungus identification isolated from the larval food of our native Indo-Malaya stingless bee, Heterotrigona itama (Hymenoptera: Apidae), is poorly understood. Hence, this study was conducted to determine the effect of fungus isolated from the stingless bee larval food on the survival of H. itama larvae and identify the isolated fungus using both morphological and molecular analyses. Methodology and results: Elisa plates designed with F-bottom type were used as artificial brood cells in a controlled condition. The eggs transferred to Elisa plates were kept in the incubator with 75%-100% humidity and 25 ± 2.5 °C of temperature. This study carried out in three different treatments: (1) microbes-free larval food, (2) fresh larval food and (3) microbes-free larval food with fungus supplement. Results showed that the survival of H. itama larvae depends on the presence of beneficial fungus with the highest survival rate (Treatment 2 = 85.71%). The absence of the beneficial fungus in the fluid food of H. itama showed the lowest survival rate (Treatment 1 = 37.14%). Microscopy analysis showed that the fungus had various forms, including unconjugated asci, round-shaped ascospore and pseudohyphae. The molecular characterisation of the isolated fungi was performed using 23S rRNA gene sequencing using universal primers ITS1 and ITS4. DNA barcoding of three isolated fungi confirmed all isolated fungi matched Panus lecomtei (Basidiomycetes; Poriales; Polyporaceae) with 99.70% of similarity. Conclusion, significance and impact of study: This study provides information on the importance of whitish fungus in appearance that existed in the brood cell, which is proposed to be the crucial component of in-vitro stingless bee queen rearing protocol.