Nurse-bees and Circadian Rhythms

I read this SciAm interview about how, apparently, nurse-bees can switch off their sleep-wake cycles when their duties call for this. The paper was published in The Journal of Neuroscience. This is going to be more chronobiology, so here’s some background:

Bees (and ants and termites) are social organisms, which means that there is a neat division of labour between individuals in the colony. There are foragers, guards and – what were studied here – nurse bees. It should be obvious what each of these worker groups does.The nurse bees are in charge of looking after the newly hatched bees.

Some more information: Human babies have no circadian rhythms for the first month or so after they are born. (Not very surprising, perhaps, if you’ve been around infants. I haven’t; so it was to me.) From what I gathered, newly hatched bees are similar, with no circadian rhythms, which means that nurse-bees are forced to be active throughout the day. They do this by napping for very short periods of time (five minutes to half an hour) throughout the day, the article says.

Guy Bloch, the researcher who was interviewed (from The Alexander Silberman Institute of Life Sciences at Hebrew University, Jerusalem. The SciAm article doesn’t say this; I had to Google), says that this behavioural pattern among nurse-bees has been known for some time now. What the present work is looking to do is to find out how the information that somebody needs to be taken care of is conveyed to the nurse-bees, and how these bees manage to do this without losing cognitive performance.

What that last part means is this: try sleeping and working for durations of an hour for a full day, and see how you do. You’d suck. Okay, but that’s us human beings, with our resource-hungry brain and all its complex chemistry. It turns out that even fruitflies (Drosophila, anyone?) can’t manage this feat of switching off their circadian rhythms when necessary. There are other animals that can do this, though. (I’ve already hinted at some examples. Go read the article!)

Anyway, what did they find out about how this happens? Here’s what they found wasn’t the cause: It’s not the age of the bees, or visual cues, auditory cues or pheromones. They eliminated these (very cleverly; but that may just be the non-biologist in me talking) by first putting identical bees in empty honey cages in the same hive as where the nurse bees were. These control-bees had proper sleep-wake cycles. That takes out the age of the bees as a factor. Visual cues are taken out because the hive is dark. It’s not pheromones because the control bees were normal in their rhythms. (I’ll come back to auditory cues at the end.)

They also took out nurse-bees and put them outside contact with the hive, and found that their circadian rhythms returned; they behaved like foragers. Which tells you something about the social evolution of these animals. This also suggests that the work-around-the-clock ability has something to do with direct contact with the infant bees. The researchers think that chemical signals are probably involved, especially transmitted through antennae or through gustatory sensors in the mouth (tongues, for humans!)

Now, about the auditory signals: The researcher who was interviewed says (or at least the article quotes him as saying) that auditory cues are unlikely because ‘the hive is so noisy’. I’m sorry, but unless they’ve actually done some sort of analysis of noise patterns in hives, and are only trying to make it intelligible to laypersons (more like 7th graders, but never mind that), ‘so noisy’ is useless. The SciAm article doesn’t say if they have done any analysis of the noise. I will have to look at the J.Neuroscience article itself, if JNC has a subscription.


2 thoughts on “Nurse-bees and Circadian Rhythms”

  1. Interesting article. Pheromones were found to have profound effects on the behaviour of the bees ; they might affect the gene expression of clock proteins responsible for the circadian rhythms. Quantitative estimates of the auditory signals would be useful.

  2. You should read the actual article. I just did. It has so much more than the interview. They didn’t do any analysis of the auditory signals. But they also don’t say that auditory signals should be ruled out. The interview’s wrong at quite a few places.

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