The Importance of Time and Place: Nutrient Composition and Utilization of Seasonal Pollens by European Honey Bees (Apis mellifera L.)

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

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

Amino acids present in each pollen type.

<p>Amino acids present in each pollen type.</p

Honey bee (<i>Apis mellifera</i>) nurses do not consume pollens based on their nutritional quality

<div><p>Honey bee workers (<i>Apis mellifera</i>) consume a variety of pollens to meet the majority of their requirements for protein and lipids. Recent work indicates that honey bees prefer diets that reflect the proper ratio of nutrients necessary for optimal survival and homeostasis. This idea relies on the precept that honey bees evaluate the nutritional composition of the foods provided to them. While this has been shown in bumble bees, the data for honey bees are mixed. Further, there is controversy as to whether foragers can evaluate the nutritional value of pollens, especially if they do not consume it. Here, we focused on nurse workers, who eat most of the pollen coming into the hive. We tested the hypothesis that nurses prefer diets with higher nutritional value. We first determined the nutritional profile, number of plant taxa (richness), and degree of hypopharyngeal gland (HG) growth conferred by three honey bee collected pollens. We then presented nurses with these same three pollens in paired choice assays and measured consumption. To further test whether nutrition influenced preference, we also presented bees with natural pollens supplemented with protein or lipids and liquid diets with protein and lipid ratios equal to the natural pollens. Different pollens conferred different degrees of HG growth, but despite these differences, nurse bees did not always prefer the most nutritious pollens. Adding protein and/or lipids to less desirable pollens minimally increased pollen attractiveness, and nurses did not exhibit a strong preference for any of the three liquid diets. We conclude that different pollens provide different nutritional benefits, but that nurses either cannot or do not assess pollen nutritional value. This implies that the nurses may not be able to communicate information about pollen quality to the foragers, who regulate the pollens coming into the hive.</p></div

Pesticide content (ppb) of the three pollens.

<p>Pesticide content (ppb) of the three pollens.</p

Diversity of pollen grains in pollens based on light microscopy and ITS sequencing.

<p>Diversity of pollen grains in pollens based on light microscopy and ITS sequencing.</p

Fatty acids (FAs) present in the different pollen types.

<p>Fatty acids (FAs) present in the different pollen types.</p

Pollen (g) consumed by bees in each cage in choice assays.

<p>Consumption is shown for each cage for pairwise comparisons between (A) almond and desert, (B) desert and SE, or (C) almond and SE pollens. Average (AV) consumption over all cages is also shown. For each panel, both types of pollen were provided <i>ad libitum</i> and the total amount of pollen consumed over 7d was recorded. For panels A and B, there were significant differences in consumption (p<0.001). In panel C, consumption did not differ. Experiments in panel C were conducted in two different trials at two different times.</p

Average pollen (g) consumed by bees in each in supplemented pollen choice assays.

<p>Both types of pollen were provided <i>ad libitum</i> and the total amount of pollen consumed over 7 days was recorded. The error bars represent the S.E. around the mean consumption. Significant differences (p<0.0001) were observed in all comparisons. “SE” indicates pollen from the Southeastern United States.</p

Honey bee (<i>Apis mellifera</i>) nurses do not consume pollens based on their nutritional quality - Fig 2

<p><b>Hypopharyngeal gland (HG) sizes differed according to diet when consumption was not (A) or was (B) accounted for.</b> Gland size is represented by the least square (LS) mean estimate of (A) the square root transformed average acinus size (mm²) or (B) the average acinus size (mm²) relative to pollen type (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0191050#sec002" target="_blank">methods</a>). Bees were fed for 8d on each of the three diets. “SE” indicates pollen from the Southeastern United States. Bars with different letters are significantly different (p<0.05). Error bars represent S.E. around the LS mean values.</p