Effects of essential amino acid supplementation to promote honey bee gland and muscle development in cages and colonies.

There is growing concern about the impact of poor nutrition on honey bee health. With caged bee experiments and whole-colony field experiments, we examined the effects of supplementing bees with essential amino acids (EAA), or a control treatment of nonessential amino acids (NAA). Caged bees fed EAA developed significantly greater head weights than controls, weights that were similar to nurse bees. Caged bees fed EAA developed significantly greater thorax weights than controls, weights that were similar to foragers. Higher head and thorax weights may respectively reflect increased glandular development in nurse bees and higher flight muscle mass in forager bees. In our field study, 29% of the pollen collected by our honey bee colonies came from eucalyptus trees. Amino acid analyses revealed no EAA deficiencies for the bee-collected polyfloral pollen or for monofloral eucalyptus pollen. Colonies fed 29 g EAA supplement may have slightly increased individual bee growth and brood rearing, but this effect was not significant. A clear colony result was a correlation between nurse bee physiology and brood development: 17% increase in nurse bee weight corresponded to 100% more capped brood cells (R2 = 0.38). We suggest that colony supplementation should target nurse bee nutrition. Nurse bees eventually become forager bees. Hence, increased glandular development may support colony brood development and greater flight muscle mass may assist colony foraging.

Nutritional aspects of honey bee-collected pollen and constraints on colony development in the eastern Mediterranean.

Pollen is the main protein and lipid source for honey bees (Apis mellifera), and nutritionally impoverished landscapes pose a threat to colony development. To determine colony nutritional demands, we analyzed a yearly cycle of bee-collected pollen from colonies in the field and compared it to colony worker production and honey bee body composition, for the first time in social insects. We monitored monthly bee production in ten colonies at each of seven sites throughout Israel, and trapped pollen bi-monthly in five additional colonies at each of four of these sites. Pollen mixtures from each sampling date and site were analyzed for weight, total protein, total fatty acids (FAs), and FA composition. Compared to more temperate climates, the eastern Mediterranean allows a relatively high yearly colony growth of ca. 300,000-400,000 bees. Colonies at higher elevation above sea level showed lower growth rates. Queen egg-laying rate did not seem to limit growth, as peaks in capped brood areas showed that queens lay a prolific 2000 eggs a day on average, with up to 3300 eggs in individual cases. Pollen uptake varied significantly among sites and seasons, with an overall annual mean total 16.8kg per colony, containing 7.14kg protein and 677g fat. Overall mean pollen protein content was high (39.8%), and mean total FA content was 3.8%. Production cost, as expressed by the amount of nutrient used per bee, was least variable for linoleic acid and protein, suggesting these as the best descriptive variables for total number of bees produced. Linolenic acid levels in pollen during the autumn were relatively low, and supplementing colonies with this essential FA may mitigate potential nutritional deficiency. The essentiality of linoleic and linolenic acids was consistent with these FAs' tendency to be present at higher levels in collected pollen than in the expected nutrients in bee bodies, demonstrating a well-developed adjustment between pollinator nutritional demands and the nutritional value of food offered by pollinated plants.

Effect of stacked insecticidal Cry proteins from maize pollen on nurse bees (Apis mellifera carnica) and their gut bacteria.

Honey bee pollination is a key ecosystem service to nature and agriculture. However, biosafety research on genetically modified crops rarely considers effects on nurse bees from intact colonies, even though they receive and primarily process the largest amount of pollen. The objective of this study was to analyze the response of nurse bees and their gut bacteria to pollen from Bt maize expressing three different insecticidal Cry proteins (Cry1A.105, Cry2Ab2, and Cry3Bb1). Naturally Cry proteins are produced by bacteria (Bacillus thuringiensis). Colonies of Apis mellifera carnica were kept during anthesis in flight cages on field plots with the Bt maize, two different conventionally bred maize varieties, and without cages, 1-km outside of the experimental maize field to allow ad libitum foraging to mixed pollen sources. During their 10-days life span, the consumption of Bt maize pollen had no effect on their survival rate, body weight and rates of pollen digestion compared to the conventional maize varieties. As indicated by ELISA-quantification of Cry1A.105 and Cry3Bb1, more than 98% of the recombinant proteins were degraded. Bacterial population sizes in the gut were not affected by the genetic modification. Bt-maize, conventional varieties and mixed pollen sources selected for significantly different bacterial communities which were, however, composed of the same dominant members, including Proteobacteria in the midgut and Lactobacillus sp. and Bifidobacterium sp. in the hindgut. Surprisingly, Cry proteins from natural sources, most likely B. thuringiensis, were detected in bees with no exposure to Bt maize. The natural occurrence of Cry proteins and the lack of detectable effects on nurse bees and their gut bacteria give no indication for harmful effects of this Bt maize on nurse honey bees.

Testing pollen of single and stacked insect-resistant Bt-maize on in vitro reared honey bee larvae.

The ecologically and economic important honey bee (Apis mellifera) is a key non-target arthropod species in environmental risk assessment (ERA) of genetically modified (GM) crops. Honey bee larvae are directly exposed to transgenic products by the consumption of GM pollen. But most ERA studies only consider responses of adult bees, although Bt-proteins primarily affect the larval phases of target organisms. We adopted an in vitro larvae rearing system, to assess lethal and sublethal effects of Bt-pollen consumption in a standardized eco-toxicological bioassay. The effects of pollen from two Bt-maize cultivars, one expressing a single and the other a total of three Bt-proteins, on the survival and prepupae weight of honey bee larvae were analyzed. The control treatments included pollen from three non-transgenic maize varieties and of Heliconia rostrata. Three days old larvae were fed the realistic exposure dose of 2 mg pollen within the semi-artificial diet. The larvae were monitored over 120 h, until the prepupal stage, where larvae terminate feeding and growing. Neither single nor stacked Bt-maize pollen showed an adverse effect on larval survival and the prepupal weight. In contrast, feeding of H. rostrata pollen caused significant toxic effects. The results of this study indicate that pollen of the tested Bt-varieties does not harm the development of in vitro reared A. mellifera larvae. To sustain the ecosystem service of pollination, Bt-impact on A. mellifera should always be a crucial part of regulatory biosafety assessments. We suggest that our approach of feeding GM pollen on in vitro reared honey bee larvae is well suited of becoming a standard bioassay in regulatory risk assessments schemes of GM crops.