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Monday, September 8, 2014

Something Cool I Learned about Bees

The amazing thing about bees is that there is always something new to learn. My new discovery yesterday was that the African Honeybee or AHB (A. m. scutellata), that bee that we all dread here in the States, is threatened in in its South African homeland. Apparently, South Africa is also home to another species of honeybee called the Cape bee (A. m. capensis) that is able to take over AHB nests due to an ability called thelytoky.

Image of Cape bees from
Wikipedia. http://upload.wikimedia.org/wikipedia/commons/thumb/0/0a/
Cape_Honeybee_gorging.jpg/330px-Cape_Honeybee_gorging.jpg

Thelytowhat? Yeah, I had to look that up, too. I learned that thelytoky is a kind of parthenogenesis in which female are produced from unfertilized eggs.

As you may know, in honeybees, diploid eggs (fertilized eggs that have two sets of chromosomes) are female bees. Haploid eggs (unfertilized eggs with one set of chromosomes) become drones. When an unmated European worker starts laying, she lays haploid eggs only. This is not always so with the Cape bee, which has a frequent rate of  thelytoky (pronounced thə-ˈlit-ə-kē). Once in a while, this trait occurs with the European honeybees that we all know and love, too, but it's a very rare occurrence with our bees.

According to Wikipedia, "Not all (Cape bee) workers are capable of thelytoky - only those expressing the thelytoky phenotype, which is controlled by a recessive allele at a single locus (workers must be homozygous at this locus to be able to reproduce by thelytoky)."

I'm not a fancy scientist or anything, but hopefully, I've retained enough from biology classes to explain it more simply (though with far more many words). Diploid organisms have two sets of chromosomes. Every chromosome has two genes and consequently two alleles that control various physical attributes of the organism. (Alleles are variants of genes. I heard an analogy that explains alleles like this: Think of a gene like a shoe. An allele would be a kind of shoe -- sneakers, dress shoes...) When the alleles are the same, that trait is said to be homozygous (e.g., wearing two sneakers). When they are different, the organism is heterozygous for that trait (e.g., wearing a sneaker and a flip flop).

Some alleles are recessive, some are dominant. The dominant trait is the one that gets exhibited in the observable characteristics of that organism (i.e., phenotype). For example, alleles for black or brown hair are dominant. The ones for blonde or red are recessive. So if someone has one allele for brown hair and one for blonde, they'll end up with brown hair. In order to have blonde or red hair, a person needs two recessive alleles.

In some cases, phenotypes are controlled by multiple alleles. For example, eye color is one of these things. Have you ever noticed the wide variety of eye color shades in people's eyes, though? Just look at blue eyes. Some people have intense deep blue eyes. Other blue eyes are more pale and watery. Some are in between. Some are mixed with green, and so on. That's because eye color is influenced by multiple alleles. Other physical characteristics are caused by just one pair of alleles. I think I remember a professor saying that baldness was one of these, but don't quote me on it.

In any case, Cape bees that are capable of thelytoky have two recessive alleles at that one crucial spot in their DNA strand, so these girls are capable of laying eggs with two sets of chromosomes -- just precisely what's needed to produce workers and queens.

But why do Cape bees need this feature??? I don't remember which article it was now, but I read that the Cape area is quite windy, which leads to a low return rate from mating flights. Thelytoky allows A. m. capensis to create backups. Amazing!

The thing about the Cape bee, though, is that these laying workers use pheromonal mimicry to sneak into AHB hives where they lay eggs which are cared for by the resident African bees. Unfortunately, the mature Cape bees are underrepresented in the hive's foragers (I don't know what they do exactly), but they continue to expand and take over the colony. As fewer AHB workers are laid, the number of foraging African bees dwindles. Ultimately, the hive reaches a tipping point where there are too many Cape bees for the AHB to support, so the colony dies, and the Cape bees fly off to infest a new host.

Once again, I'm flabbergasted by the weird and wonderful life of bees.


2 comments:

  1. Wow... I did not know that about the cape bee and the AHB. I knew about thelytoky but not how it can be used to undertake a "cuckoo maneuver", Brilliant!
    I suppose though that they would also be able to pull this off with our beloved AMM too.

    So timelines so far is :
    AMM attacked by parasite - scientist makes AHB in lab - AHB escape and take over AMM hives - Cape bees pull an invasion of the body snatchers and take over AHB hive.
    So far it read like the plot of a really bad science fiction movie. What's next? Is it going to turn out that cape bees are AMM double agents?

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    1. LOL! I like your idea for a sci-fi/spy thriller. In my mind, the timeline is more like AMM attacked by parasite - scientist imports AHB which escapes and infiltrates AMM hives - scientist imports Cape bee double agent to bring down AHB - Cape bee destroys everybody. My script is more of a horror flick.

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