An Assessment of the Impacts of Feeding Four Fungal Extracts on the Lifespan and Midgut of Newly Emerged Carniolan Honey Bees (Apis mellifera carnica)

Given the current global agricultural system, honey bees are exposed to a complex network of stressors that can act simultaneously, making it challenging to maintain healthy colonies. Therefore, studies on natural products to improve colony health have increased in recent years. Among them, fungal extracts have been shown to be beneficial to honey bees. However, there remains a knowledge gap regarding lifespan and histomorphological studies in bees fed fungal extracts. Our current study aimed to assess the impacts of extracts from Ganoderma lucidum (GL), Hericium erinaceus (HE), Inonotus obliquus (IO), and Trametes versicolor (TV) on the lifespan and midgut of honey bees. Newly emerged Carniolan honey bees (Apis mellifera carnica) were fed 4% of each fungal extract until the death of the last individual to assess survival probability. For histomorphological analyses, bees were fed for 7, 14, and 21 days and sampled at these same time points. Then, the midguts were dissected and histologically processed for qualitative and semi-quantitative microscopic analyses. The results showed that the fungal extracts did not significantly affect honey bee survival, and that the histomorphology of the intestinal villi, digestive cells, and regenerative cells in bees treated with fungal extracts did not differ from that of untreated bees throughout the analyzed period. Similarly, no differences were observed in the midgut lesion index between bees treated with fungal extracts and the untreated group. Overall, the absence of harmful effects on lifespan and midgut suggests that feeding fungal extracts may be a potential alternative for supporting bee health.