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Carbohydrates are vital for honey bee energy, fitness, and survival, influencing colony dynamics and resilience. This study examined the effects of various carbohydrate sources on honeybee longevity, hypopharyngeal gland size, gene expression, and gut microbiome composition. Newly emerged bees were fed white sugar, brown sugar, corn syrup (CS), maltose, acacia honey, chestnut honey, and oligosaccharide ad libitum. Bees fed CS showed the highest longevity, followed by acacia honey and white sugar, while oligosaccharide-fed bees had the lowest longevity. CS-fed bees also exhibited larger hypopharyngeal glands, correlating with improved survival. Gene expression analysis revealed upregulation of Ilp2 and Vg and downregulation of Ilp1 in 14-day-old bees fed with CS which may be linked to enhanced longevity. Gut microbiome analysis showed the higher composition of Frischella in honey fed treatment groups and Bartonella in processed carbohydrates treated groups, potentially compensating for dietary amino acid deficiencies. However, the absence of core symbionts like Snodgrassella in CS-fed bees may weaken immunity and heighten disease susceptibility. These findings suggest starch-derived corn syrup as a promising carbohydrate source under laboratory conditions, however, long-term colony-level studies are essential to fully understand its benefits and potential risks. This research provides valuable insights for honey bee management and conservation strategies.

The aim of this study was to evaluate the effect of organic zinc and selenium on the antioxidant indices, acini size, royal jelly production, and relative expression of hsp90 and trx genes in honey bees under heat stress. Twenty five colonies were exposed to heat stress (42 °C for at least 4 h per day) and randomly divided into five treatments. Treatments were C), the control group receiving syrup without additives and other groups receiving syrup containing 2500 µg/L of zinc (T1), 5000 µg/L of zinc (T2), 500 µg/L selenium (T3), and 1000 µg/L selenium (T4). Organic zinc increased (P < 0.05), but selenium supplementation decreased (P < 0.05) the activities of thioredoxin peroxidase and catalase. Organic zinc and selenium supplements decreased (P < 0.05), the relative gene expression of hsp90 but increased (P < 0.05) gene expression of trx as compared to control. The lowest acini size was observed in C and the greatest acini size was observed in T2 (P < 0.05). Acini size increased (P < 0.05) as dose of organic zinc increased but not for selenium doses. It was concluded that supplementation of zinc at dose of 5000 µg/L and selenium at a dose of 500 µg /L has beneficial effects on producing royal jelly colonies.

Pesticide application can have an adverse effect on pollinator honey bees, Apis mellifera L., ranging from mortality to sublethal effects. Therefore, it is necessary to understand any potential effects of pesticides. The present study reports the acute toxicity and adverse effects of sulfoxaflor insecticide on the biochemical activity and histological changes on A. mellifera. The results showed that after 48 h post-treatment, the LD25 and LD50 values were 0.078 and 0.162 µg/bee, respectively, of sulfoxaflor on A. mellifera. The detoxification enzyme activity shows an increase of glutathione-S-transferase (GST) enzyme on A. mellifera in response to sulfoxaflor at LD50 value. Conversely, no significant differences were found in mixed-function oxidation (MFO) activity. In addition, after 4 h of sulfoxaflor exposure, the brains of treated bees showed nuclear pyknosis and degeneration in some cells, which evolved to mushroom shaped tissue losses, mainly neurons replaced by vacuoles after 48 h. There was a slight effect on secretory vesicles in the hypopharyngeal gland after 4 h of exposure. After 48 h, the vacuolar cytoplasm and basophilic pyknotic nuclei were lost in the atrophied acini. After exposure to sulfoxaflor, the midgut of A. mellifera workers showed histological changes in epithelial cells. These findings of the present study showed that sulfoxaflor could have an adverse effect on A. mellifera.

Division of labor within a honey bee colony creates a codependence between bees performing different tasks. The most obvious example of this is between the reproductive queen and worker bees. Queen bees lay 1,000 or more eggs a day, while young worker bees tend and feed queens. Young workers and queens can be exposed to pesticides when foragers return to the hive with contaminated resources. Previous research has found negative effects of larval exposure to insect-growth disruptors (IGD) methoxyfenozide and pyriproxyfen, on adult responsiveness to artificial queen pheromone. The present work investigates potential physiological and molecular mechanisms underpinning this behavioral change by examining the development of hypopharyngeal glands and ovaries as well as the expression of genes related to reproduction and worker endocrine signaling in the brain and hypopharyngeal gland tissues. Though hypopharyngeal gland and ovary development were not altered by developmental exposure to IGDs, gene expression differed. Specifically, in the brain tissue, ilp1 was downregulated in bees exposed to pyriproxyfen during development, and Kr-h1 was downregulated in both methoxyfenozide- and pyriproxyfen-exposed bees. In the hypopharyngeal glands, Kr-h1, EcR-A, EcR-B, and E75 were upregulated in honey bees exposed to methoxyfenozide compared to those in the pyriproxyfen or control treatments. Here we discuss these results and their potential implications for the health and performance of honey bee colonies.

Nutrition plays a major role in honey bees health, development and performance. Industrial agriculture, deforestation and climate change, however, are known to have negative impacts in natural habitats, compromising access to abundant and diversified sources of pollen and nectar, essential for honey bees. Beekeepers commonly use alternative supplementation feed, particularly during the fall and winter when resources are scarce to avoid or reduce colony loss as a consequence of starvation. The goal of the present study was to evaluate the effects of diets containing an inorganic iron source on the morphology of hypopharyngeal glands (HG) in 6-day-old honey bees during the off-season. Twelve colonies were distributed into four groups and supplemented, or not, with inorganic iron at concentrations of 0, 25, 50, and 100 ppm, diluted in sugar syrup. Six-day-old bees were then collected from each treatment, and their heads were prepared for the evaluation of the area and acini number of the HG. No significant differences were observed in the analyzed parameters of HG, regardless of the iron concentrations used (p < 0.05). In conclusion, providing an inorganic iron source during the off-season for colony nutrition does not modulate the development of the hypopharyngeal glands in 6-day-old nurse bees.

Lithium chloride (LiCl) has a high efficacy against Varroa destructor and a good tolerability for adult bees but the effect of LiCl on the honey bee brood has not been taken into consideration yet. We quantified the mortality of larvae fed with different concentrations of LiCl. For artificially reared larvae already, a concentration of 1 mM had significant toxic effects while under colony conditions, 10 mM was well tolerated. However, a chronic application of the effective concentration of 25 mM elicited brood mortalities between 60 and 90%. Shorter feeding periods of 2 or 4 days reduced the brood damages significantly. Measurements of the lithium concentrations in larvae and pupae during a chronic exposure with 10, 17.5 and 25 mM LiCl revealed respective lithium levels in 5th instar larvae of 7, 13 and 15 mg/kg. No lithium was detectable in 2-day old larvae indicating that pure worker jelly from the hypopharyngeal gland is not contaminated with LiCl. Based on these results, applications of LiCl in colonies with brood should be avoided.

Bees play a crucial role in pollination but are exposed to various pesticides during nectar and pollen collection, which can impact their health and pollination efficiency. This study aimed to investigate morphological and histochemical changes in the hypopharyngeal glands of Scaptotrigona postica after exposure to three chemical compounds: glyphosate, fipronil, and Tween. Nurse bees of S. postica were divided into four experimental groups and fed with sucrose syrup containing the compounds for 24 h. After the exposure period, the hypopharyngeal glands were analyzed for morphology using light microscopy and transmission electron microscopy. The hypopharyngeal glands of S. postica exhibited a tubuloacinar structure, with unicellular acini approximately 54 µm in diameter. Exposure to fipronil resulted in changes in the organization of the rough endoplasmic reticulum (RER) and increased area and sphericity of the acini compared to all other groups, as well as a higher presence of proteins in the cytoplasm compared to other pesticides, potentially due to increased food consumption. Bees exposed to glyphosate showed alterations in the mitochondria compared to all groups. The Tween group did not exhibit significant changes in cellular ultrastructure, only a smaller area and sphericity compared to the control group. The hypopharyngeal glands are highly sensitive to pesticides and are efficient bioindicators. Significant changes in these glands can compromise the maintenance of the colony.

A honey bee colony’s ability to grow and develop is dependent on adequate nutrition. Bees collect pollen from flowers as a source of protein, fat, vitamins, and minerals. The crude protein content of corn pollen is considered low, around 15%; however, bees frequently visit the male flowers of the tassels for pollen. In this study, we aimed for the first time to improve the nutritious value of corn pollen by mechanically crushing its external pollen wall. We then compared the effect of feeding crushed vs. non-crushed corn pollen grains on honey bee diet consumption, digestibility, hemolymph protein content, hypopharyngeal gland (HPG) size, and thorax weight under laboratory conditions. We found that crushing corn pollen grains increased diet digestibility and hemolymph protein content while decreasing honey bee pollen consumption (− 39.88%). Crushing pollen however had no effect on HPG size or thorax weight. These findings may be beneficial to beekeepers in areas where corn monoculture is prevalent. The effect of crushed corn pollen on larval development and growth, as well as colony development and vitality, should be investigated in future studies.

Hypopharyngeal gland (HPG) development in honey bee workers is primarily age-dependent and changes according to the tasks performed in the colony. HPG activity also depends on colony requirements and is flexible in relation to the need for feeding brood. Very little is known about HPG development in the honey bee subspecies found in Southern Africa. We examined HPG development in Apis mellifera scutellata and A. m. capensis, including A. m. scutellata colonies infested with an invasive parasitic clonal lineage of A. m. capensis known to manipulate food provisioning to the parasitic larvae by their A.m. scutellata hosts, under natural in-hive conditions in bees aged 0 to 14 days using light microscopy. We found marked differences in acini size (berry-like clusters of secretory cells) and the age at which maximum HPG development occurred between the subspecies and in the presence of the parasite. In A. m. scutellata workers, acini reached maximum size at 6 days. The acini of A. m. capensis workers were larger (up to double) than those of A. m. scutellata and reached maximum size at 8 days, while the HPG acini in A. m. scutellata workers infested with A. m. capensis clones reached development sizes similar to those of A. m. capensis at day 10 and were 1.5 times larger than those of uninfested A. m. scutellata. This provides foundational insights into a functional response affecting the development of the HPG most likely associated with brood pheromone composition and how this is altered in the presence of a social parasite.

Honey bee colonies have a yearly cycle that is supported nutritionally by the seasonal progression of flowering plants. In the spring, colonies grow by rearing brood, but in the fall, brood rearing declines in preparation for overwintering. Depending on where colonies are located, the yearly cycle can differ especially in overwintering activities. In temperate climates of Europe and North America, colonies reduce or end brood rearing in the fall while in warmer climates bees can rear brood and forage throughout the year. To test the hypothesis that nutrients available in seasonal pollens and honey bee responses to them can differ we analyzed pollen in the spring and fall collected by colonies in environments where brood rearing either stops in the fall (Iowa) or continues through the winter (Arizona). We fed both types of pollen to worker offspring of queens that emerged and open mated in each type of environment. We measured physiological responses to test if they differed depending on the location and season when the pollen was collected and the queen line of the workers that consumed it. Specifically, we measured pollen and protein consumption, gene expression levels (hex 70, hex 110, and vg) and hypopharyngeal gland (HPG) development. We found differences in macronutrient content and amino and fatty acids between spring and fall pollens from the same location and differences in nutrient content between locations during the same season. We also detected queen type and seasonal effects in HPG size and differences in gene expression between bees consuming spring vs. fall pollen with larger HPG and higher gene expression levels in those consuming spring pollen. The effects might have emerged from the seasonal differences in nutritional content of the pollens and genetic factors associated with the queen lines we used.