Why spin live fruit flies in centrifuge?

Question

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?

Answer 1

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.

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 mutants^29,30

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”.