While reading this most interesting article, I noted a paragraph, abbreviated here:
“In 2008, Steven Reppert and his colleagues knocked out one of the cryptochrome proteins from Drosophila and observed that they lost the ability to associate a magnetic field with a sugar reward. Reppert and several other labs spent the next 15 years studying how it contributes to the fly’s magnetic sense, but that effort fizzled out when a massive replication effort using more than 100,000 flies found no evidence that they can detect magnetic fields at all—a ‘great disappointment,’ says study investigator Peter Hore.”
The “massive replication effort” refers to “No evidence for magnetic field effects on the behaviour of Drosophila,” published in Nature in 2023. The authors, Bassetto et al., suggested that Reppert’s findings, and 14 further cited studies of magnetoreception in Drosophila, were in fact all false positives.
This was an extraordinary suggestion, given that all forms of life respond to magnetic fields and that magnetoreception in Drosophila is long established in different assays and end points, mostly outside the field of animal navigation.
Almost immediately, serious questions were raised.
I contacted Bassetto and his co-authors with two concerns: (i) an obvious error in the statistical analysis involving the misuse of p-values and (ii) the use of plastic materials in their T-maze, which are known to accumulate static electric charge and affect the normal behavior of Drosophila.
Reppert and Charalambos P. Kyriacou of the University of Leicester then voiced a range of flaws in the study design, execution and analysis, which they explained in Nature Matters Arising. Reppert pointed out that they too used a large number of flies—greater than 39,500, as can be readily calculated from the error bars in their results.
A particular criticism was that, unlike in Gegear et al., the olfactory conditioning of flies in Bassetto et al. was not carried out under the same conditions as the failed magnetic conditioning studies: the former in Oxford, England, the latter in Oldenburg, Germany. This suggests there may be other important variables that differ between the two studies.
Kyriacou also criticized the statistical analysis. In what must be a final irony, he reanalyzed the Bassetto et al. data to find that Drosophila do indeed detect magnetic fields!
I have to point to 23 other studies of magnetoreception in Drosophila, comprising many end points: movement toward a magnetic-field source; compass orientation in the geomagnetic field; effects on the circadian clock; increase in seizures and male courtship activity; geotaxis and independent replication; genetic analysis of cryptochrome and whether light is required for magnetoreception; magnetic-field-induced neuronal firing; and the effects of electromagnetic fields on oogenesis.
Many studies involve a number of separate stages. For example, Sherrard et al. employed human cryptochromes in transgenic Drosophila to demonstrate that low-intensity electromagnetic fields induce human cryptochrome to modulate intracellular reactive oxygen species.
Together, established magnetoreception in Drosophila has much to offer those with an interest in neuroscience.
Denis L. Henshaw, Fellow Collegium Ramazzini
Emeritus professor of human radiation effects
Atmospheric Chemistry Group
School of Chemistry
University of Bristol
Cantocks Close,
Bristol, BS8 1TS, United Kingdom
and
former Scientific director
CHILDREN with CANCER UK
Registered Charity Number: 298405
Inaugurated by Diana, Princess of Wales
Website: http://www.childrenwithcancer.org.uk
