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2881Re: [beemonitoring] Identifying pollen collected from bees

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  • Doug Yanega
    Aug 19 9:42 AM
      On 8/18/13 8:05 AM, Laura Russo wrote:
      Dear all,

      I am interested in identifying pollen samples collected from bees.  I have looked at some resources on the internet, but I thought I would probe this listserve to see if anyone has had experience with that process, and therefore recommendations for resources (i.e. books, websites, people, etc.).

      Any advice on the collection methodology would also be gratefully received.
      I'll offer my own experience in two techniques, one of which is an example of the lowest-tech option (which I imagine many here will scoff at), and you'll have to determine for yourself whether either is a viable approach in your case.

      When I was interested in this type of analysis, I took a course in palynology, and found the techniques - all of which centered around acetolysis - to be time-consuming, somewhat costly (I was doing research out-of-pocket), and poorly suited for very tiny quantities of pollen. Kearns & Inouye was not yet in print back in 1983, so I was flailing about a bit and had to devise my own approach.

      (1) Working with pinned museum specimens of bees, the number of pollen grains available can be very small, and the technique I used was to take an SEM stub with double-sided sticky tape and scrape pollen onto it directly. While these samples could not be examined under a light microscope, and while they didn't have the outer surfaces completely clean, they could still be viewed under the SEM just fine, if I could find someone who would let me have a few minutes of SEM time (which was infrequent, so I didn't get to make much use of this).

      (2) for wild-caught bees (whose behavior I was observing) I used regular scotch tape, rubbed the bee gently against a small piece of scotch tape (technically, "magic transparent" tape which can be written on) to produce a pollen smear, released the bee, and stuck the piece of tape to a microscope slide. I wrote the ID of the bee and the date and time on the piece of tape in pencil. The pollen was viewed by flipping the slide over. These samples were untreated, and that has drawbacks, but it took less than a minute to gather a sample, from catching the bee to having the sample mounted and labeled.

      In both cases, some reference images or samples are needed, using pollen grains that have been *similarly untreated* (no acetolysis). Perhaps things have changed since I did this work (back in the 1980's), but I found there to be very few publications with SEM photos of raw pollen grains, and there was (and probably still is) absolutely nothing published showing raw pollen under a light microscope. In the former case, I ended up with many unidentifiable pollen types, but for my purposes it was still enough to know whether a given bee was foraging on multiple pollen sources or not (i.e., I had a very specific question, and knowing the plant ID would've been great, but not essential for those samples). In the latter case, I systematically went around in the habitat in question and took samples of pollen directly from the anthers of all the flowering plants in bloom within about 100 meters of the nest site to create a reference collection. This actually proved to be very effective, allowing me to identify the source of over 80% of the collected samples with an extremely minimal amount of time, energy, or expense - OR disruption of the behaviors I was observing (most females would, after a short interval, return to their nest, deposit the pollen load from which I had removed a smear, and then resume foraging).

      I haven't stayed abreast of recent advances, so can't speak as to how comparable my solution is to the methods used by others. I will note that - out of curiosity - I just pulled out my slides and looked at them under a scope, and aside from strong fading of the color, they look pretty much the same as they did nearly 30 years ago when I collected them. Scotch tape is about as low-tech as one can get, and it looks pretty good as a research tool. ;-)

      Doug Yanega      Dept. of Entomology       Entomology Research Museum
      Univ. of California, Riverside, CA 92521-0314     skype: dyanega
      phone: (951) 827-4315 (disclaimer: opinions are mine, not UCR's)
        "There are some enterprises in which a careful disorderliness
              is the true method" - Herman Melville, Moby Dick, Chap. 82
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