This past summer, the HMC Bee Lab ran an experiment on the importance of communication for honey bee foraging success. One of the ways we want to determine a bee colony’s “success” is by looking at the diversity of pollen collected. So why do we care about pollen diversity? How is it related to the health of a honey bee colony?
Honey bees collect flower nectar and pollen for their food. Nectar is converted into honey, the bees’ main source of carbohydrates, while pollen is converted into bee bread, and is the bees’ main source of protein. In addition, bee bread also provides lipids, some minerals, and some vitamins. Think about your balanced diet: you need to eat a variety of food groups to consume all the necessary macromolecules. Bees are the same. They complete their balanced diet by gathering pollen and consuming bee bread (source 1).
The protein supplied by pollen is essential for brood production, bee development, and hive growth. However, the amount of protein provided in different kinds of pollen is highly variable; in other words, some plants will provide pollen with very little protein, while others will provide a large amount of protein in each pollen grain. Furthermore, pollen from different species of plants contains different amino acids. Because the composition of pollen varies between plant species, diversity of pollen collected is required to meet all of the bees’ nutritional needs (source 2).
In our experiment, we wanted to see if there would be a difference in pollen foraging success – indicated by a difference in pollen diversity – between bee colonies with communication and without communication. To do so, we used a “pollen trap” (source 3) to collect the pollen gathered by the bees in one day during each experimental treatment. The pollen trap is a gate-like structure that attaches to the hive entrance. It forms a grill in front of the hive. Bees are small enough to slip in and out of the hive, but bees with pollen baskets attached to their legs are too wide to pass through, so the pollen is brushed off the bee into a collection basket below the entrance. The video linked below by ANEL Co Beekeeping Supplies provides a good visual of what we were doing. The next day, we empty the baskets and store the pollen loads in the fridge for further analysis.
Currently, we are trying to analyze the multiple batches of pollen we collected to see whether they differ in diversity. We want to somehow find out what type of pollen is present, and how much of each type is present. To do this, we are using two methods:
- Random sampling and pollen grain identification;
- Computerized image analysis
The first method is taking a (hopefully representative) random sample from all the pollen loads collected, and looking at the individual pollen grains under a microscope. We can identify which plant the pollen grain comes from by its characteristics.
The second method is a new method we are trying to develop. The idea is to automate the process with some computer program, and quickly determine the proportions of different coloured pollen present in a picture. However, this method relies on the assumption that a single coloured pollen load corresponds to one type of pollen grain from one species of plant. Since we are not sure if this method will work, Tessa is analyzing the pollen from certain color groups using the first method to confirm whether this assumption is correct.
I am working on the image analysis technique. It’s definitely still a work in progress, but this is what we have so far!
We start with these images of pollen:
We can use the particle analysis feature (link) on ImageJ (link) to report the pixel coordinate of the center of each pollen load:
Thanks to Alasdair, we have a Python script that can take a pixel coordinate and calculate the RGB values around that coordinate. This way, we can find the average RGB values of all the individual pollen loads. We still need to figure out how to divide the spectrum of pollen load colors into distinct group, which involves fiddling with some parameter values and improving our Python script. However, it feels fairly promising so far!
Both methods of finding pollen diversity are quite involved. However, we think that if we can get the image analysis method to work, then we can get a more complete understanding of the pollen diversity collected by honey bees in less time. Fingers crossed this method works!
Further readings:
Paper about waggle dances, honey bees, and pollen diversity: Donaldson-Matasci M, Dornhaus A (2014) Dance Communication Affects Consistency, but Not Breadth, of Resource Use in Pollen-Foraging Honey Bees. PLoS ONE 9(10): e107527. doi:10.1371/journal.pone.0107527
A quick summary of multiple pollen studies: Collison, C. (2016). Pollen Quality. Bee Culture: The magazine of American beekeeping. Web. http://www.beeculture.com/pollen-quality/
References:
Source 1 - Blog post about the pollen: Snyder, R. (2012). Nectar, pollen, and pollen substitute: Keys to a healthy colony. Bee informed. Web. https://beeinformed.org/2012/12/05/nectar-pollen-and-pollen-substitute-keys-to-a-healthy-colonly/
Source 2 - Information on pollen: Ellis, A., Ellis, J., O'Malley, M., Nallen, C. Z. (2013). The Benefits of Pollen to Honey Bees. Entomology and Nemotology Department, UF/IFAS Extension. http://edis.ifas.ufl.edu/in868
Source 3 - Information on pollen traps: Pollen traps require constant attention. Honey Bee Suite: A better way to bee. Web. http://honeybeesuite.com/pollen-traps-require-constant-attention/
Video of pollen trap: https://www.youtube.com/watch?v=XfZONmpcXyU
No comments:
Post a Comment