Microalgae functional feed additives strengthen immunity and increase longevity in honey bees

Authors: MARTIN EWERT, ALLYSON - US Department Of Agriculture (USDA); MCMENAMIN, ALEXANDER - US Department Of Agriculture (USDA); ADJAYE, DANIELA - US Department Of Agriculture (USDA); RAINEY, VICTOR - US Department Of Agriculture (USDA); Ricigliano, Vincent

Submitted to: Journal of Invertebrate Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/2/2025
Publication Date: N/A
Citation: N/A

Interpretive Summary: Disease and poor nutrition threaten the vital role that honey bees contribute to pollinating most of what we eat. Better nutrition can help bees stay healthy. Therefore, USDA researchers evaluated the benefits of enhancing bee diets with nutrient-rich natural microalgae supplements. Although bees fed pollen lived the longest, those fed certain microalgae mounted stronger immune responses and better cleared bacterial infections. If these results predict success in real-world conditions, supplementing bee diets with microalgae may help honey bees thrive in the face of disease and environmental stress. This information will benefit beekeepers, manufacturers of bee feed supplements, growers of fruits, vegetables, and nuts, and the public at large who seek healthy, affordable produce and a healthy environment.

Technical Abstract: Honey bees (Apis mellifera) are faced with a myriad of immunological threats, often worsened by poor nutrition. The use of functional feed additives offers a promising strategy to address colony nutritional deficiencies while helping strengthen bee immune responses and mitigate stress. Microalgae have gained recognition as beneficial diet ingredients for livestock due to their abundance of essential nutrients and immunomodulatory properties. Here, we tested the effects of microalgae-containing feed on honey bee immunity and lifespan. Caged bees were fed a commercial artificial diet or the same diet with added pollen, spirulina (Arthrospira platensis) or Chlorella (Chlorella vulgaris). Immune-related gene expression and longevity were measured following six days of ad libitum feeding. While pollen-fed bees lived the longest (median lifespan = 51 days), bees fed spirulina and Chlorella lived significantly longer (median lifespan = 48 and 46 days, respectively) than bees fed the base diet (median lifespan = 40 days). Spirulina-fed bees exhibited significantly higher expression of several antimicrobial peptide (AMP) genes relative to the base diet and had superior bacterial clearing ability when challenged by injection with live E. coli cells. We propose that this increased immunocompetence is at least partially due to elevated AMP levels and we extrapolate from spirulina-induced immune stimulation described in other invertebrates. Our findings suggest that the tested microalgae can improve honey bee longevity and immune functions with negligible health costs relative to a commonly used artificial diet. Determining the effects of microalgae feed additives in field-relevant contexts and in the face of diverse pathogen challenges should be the focus of future research efforts.