1
$\begingroup$

I was reading this article about the evolution of monarch butterflies’ resistance to cardiac glycosides: These Butterflies Evolved to Eat Poison. How Could That Have Happened?

And this passage made me curious:

The researchers put the mutant flies in a centrifuge and spun them for ten seconds. Afterward, the flies were overwhelmed by seizures for several minutes.

Ordinary flies, by contrast, immediately walked away from the laboratory carnival ride. Flies with the other two resistance mutations were also unharmed by the procedure.

Given that normal fruit flies are usually unharmed by the centrifuge, what made the researchers decide to spin the flies? I’m not a biologist, I’m a software engineer. So I’m just guessing that it might be a standard lab procedure when studying fruit flies. Assuming the researchers didn’t know the flies with mutation 122 alone would experience seizures, what do researchers usually expect to gain from spinning live flies in a centrifuge?

$\endgroup$
9
$\begingroup$

Correction of Poster’s Source

The article cited mistakenly refers to centrifugation, however the actual procedure used in the work — Karageorgi et al. Nature, 2 Oct 2019 — is vortexing, as illustrated in Fig. 3 of the paper below.

Vortexing Drosophila

What is meant by standard lab procedure?

There is no such thing as standard lab procedure. There are standard lab procedures for performing certain kinds of experiments or processes.

In studying the effect of mutations on the behaviour of live fruit flies one devises laboratory procedures that are, if at all possible, cheap and easy to perform on many animals. All laboratories have vortex mixers of the type illustrated, as these are used to speed up dissolution of solutes and to disperse (resuspend) solids which have been precipitated by centrifugation — perhaps the source of confusion as the flies would likely have been put in centrifuge tubes as these would be appropriate (although the flies were not subjected to centrifugation).

Why vortex flies?

The vortexing is what is apparently called a ‘Bang’ assay — a means of testing flies for neurological seizures. The authors state:

To investigate this, we phenotyped monarch lineage knock-in flies for neurological seizures upon shaking (bang sensitivity), a common phenotype in hypomorphic Na+/K+-ATPase mutants29,30

Without consulting references 29 and 30, it seems clear that the authors were expecting cardiac glycosides to produce neurological seizures, and used a simple technique that had been used previously by others to assay this.

So, yes, if you are interested in these aspects of fly physiology vortexing may be a standard laboratory technique, but, no, other fly labs (e.g. those studying the gut) don’t start the morning by saying:

“Lets take the new mutant for a spin”.

$\endgroup$
  • $\begingroup$ Awesome! I did pull up the actual paper and tried to find the word “centrifuge” (and related forms). No wonder I couldn’t find it! $\endgroup$ – Kal Oct 3 '19 at 23:41
  • 1
    $\begingroup$ I don't know the exact history, but I wouldn't be surprised if this started as "shake them in the tube a little bit" maybe even initially as a complete accident, and the mechanical option was an attempt to standardize a bit. $\endgroup$ – Bryan Krause Oct 4 '19 at 0:58
  • $\begingroup$ In the field of Drosophila neuroscience, vortexing is also a standard treatment to disorient flies, for some decades already. It is, for instance, used in assays for measuring motor functions following a 'reset', or looking at orientation based on mechanosensation, vision and olfaction, and also as a punishment or an aversion stimulus in classical conditioning/learning studies. Vortexing is an easy and reproducible way to standardize what is essentially just vial shaking. Also crucially, centrifuging is a very common lab misnomer for vortexing (source: my experience in quite a few labs). $\endgroup$ – S Pr Oct 4 '19 at 11:48
  • 2
    $\begingroup$ @SPr — I've never encountered the confusion you mention. I suppose it depends on the type of lab and perhaps nationality. In the biochemical labs I worked in the use of ultracentrifuges and large centrifuges was so central (long before the small desktop centrifuges were developed) that nobody would refer to a vorted mixer (the original was a "whirlimixer") as a centrifuge. It only appeared in the early 60s, whereas Morgan reported the use of the centrifuge to inflict changes on Drosophila eggs in 1902. $\endgroup$ – David Oct 4 '19 at 12:24

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.