Dietary Phytochemicals, Honey Bee Longevity and Pathogen Tolerance

Abstract

Continued loss of natural habitats with native prairies and wildflower patches is eliminating diverse sources of pollen, nectar and phytochemicals therein for foraging bees. The longstanding plant-pollinator mutualism reiterates the role of phytochemicals in sustaining plant-pollinator relationship and promoting honey bee health. We studied the effects of four phytochemicals—caffeine, gallic acid, kaempferol and p-coumaric acid, on survival and pathogen tolerance in the European honey bee, Apis mellifera (L.). We recorded longevity of worker bees that were provided ad libitum access to sugar solution supplemented with different concentrations of phytochemicals. We artificially infected worker bees with the protozoan parasite, Nosema ceranae. Infected bees were provided access to the same concentrations of the phytochemicals in the sugar solution, and their longevity and spore load at mortality were determined. Bees supplemented with dietary phytochemicals survived longer and lower concentrations were generally more beneficial. Dietary phytochemicals enabled bees to combat infection as seen by reduced spore-load at mortality. Many of the phytochemicals are plant defense compounds that pollinators have evolved to tolerate and derive benefits from. Our findings support the chemical bases of co-evolutionary interactions and reiterate the importance of diversity in floral nutrition sources to sustain healthy honey bee populations by strengthening the natural mutualistic relationships.

Extracts from Eleutherococcus senticosus (Rupr. et Maxim.) Maxim. Roots: A New Hope Against Honeybee Death Caused by Nosemosis

“…and Aster scaber Thunberg, at non-toxic concentrations, proved to show anti-nosemosis effects [ 28 , 29 ]. In several studies, essential oils such as mint ( Mentha pepper L.), melissa ( Melissa officinalis L.), coriandrum ( Coriander sativum L.), thyme ( Satureja hortensis L.) oils, other phytochemicals such as caffeine, clove oil, gallic acid, kaempferol and p-coumaric acid, and even propolis expanded honeybee longevity and to some extent, reduced nosemosis levels [ 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 ]. Such phytochemicals as clove oil, laurel extract and sulforaphane, moderately decreased Nosema -infection, but at the same time, strongly reduced honeybee lifespan [ 33 , 36 , 37 ].…”

Ameliorative Effects of Phytochemical Ingestion on Viral Infection in Honey Bees

“…The screening process also revealed that neither p -coumaric acid nor quercetin were capable of improving the survivorship of honey bees inoculated with IAPV ( Figure 1 D). Both of these phytochemicals possess multiple survivorship-boosting capabilities, including reducing N. ceranae spore load, upregulating detoxification genes, and increasing pesticide tolerance [ 25 , 26 , 27 , 29 ]. Furthermore, they both inhibit the replication and production of a large number of viruses, such as Canine Distemper Virus [ 30 ], human rhinovirus [ 31 ], herpes simplex virus [ 63 ], and Japanese encephalitis virus [ 64 ], although these tests have thus far been conducted only in mammalian systems.…”

“…Both, when ingested, upregulate genes that encode cytochrome P450 monooxygenase enzymes, which are responsible for the detoxification of xenobiotics [ 25 , 26 , 27 ]. PCA also upregulates antimicrobial peptide gene expression when fed to larval and adult bees [ 25 , 28 ] and improves honey bee survivorship when infected with Nosema ceranae microsporidian gut parasites [ 29 ]. Both PCA and quercetin have also been shown to possess antiviral qualities; however, these studies have primarily been conducted in human pathogen models (e.g., cell culture systems with model human viruses) [ 30 , 31 ] and not pollinators that normally collect and consume these phytochemicals.…”

“…Balieira et al [ 41 ] showed that caffeine helps to ameliorate the oxidative stress induced by the neonicotinoid insecticide imidacloprid. Both Strachecka et al [ 42 ] and Bernklau et al [ 29 ] found that caffeine increased the lifespan of honey bees infected by N. ceranae by reducing spore loads. However, very few studies have examined the effects of caffeine on virus infection, with only one other study showing that it can inhibit DWV replication and upregulate immunity genes [ 43 ].…”

For antagonists and mutualists: the paradox of insect toxic secondary metabolites in nectar and pollen

“…More recently caffeine is reported to be a potential antimicrobial that could reduce disease load in honeybees caused by Nosema bombi (Dissociodihaplophasida: Nosematidae) (Bernklau et al 2019) thereby offering an additional benefit to the pollinators that provide this most important service to plants. Although Richardson et al (2015a, b) reported no effect against another parasite, Crithidia bombi (Trypanosomatida).…”