French scientists have taken nuclear magnetic resonance spectra of live water fleas, a step which could have implications for environmental studies.

In a collaboration between the Research Center of the Armed Forces' Health Service in La Tronche, and Cemagref, Lyon, Andrei Bunescu and colleagues used proton high resolution magic-angle spinning (HRMAS) NMR to provide a metabolomic profile of the freshwater organism, Daphnia magna. Although proton NMR has previously been used for similar studies, the broad signals meant the spectra were very difficult to quantify. By spinning the samples at the so-called magic angle of 54.7°, Bunescu and colleagues were able to obtain higher resolution spectra and detect lipids within the fleas.

NMR spectra show that water fleas have increased lipid levels just before egg laying

The team determined the optimum parameters that would allow the water fleas to remain unaffected by the procedure. They found that anaesthetising the organisms and spinning the samples at speeds of 2000Hz or less for a maximum of three hours resulted in a survival rate comparable to control samples. 'The surviving daphnids presented a normal life cycle, as they developed eggs and embryos as the control organisms did,' explains Bunescu. 

The group compared NMR spectra of 1- and 7-day-old daphnids. They observed higher lipid levels in the spectra from older fleas, which they attributed to the presence of eggs in these organisms. 'Lipids play an important role in the reproduction capability of daphnids,' explains Bunescu. 'The lipid level inside daphnids is the highest just before egg laying.'

The team suggests that the procedure may provide information on the effects of chemicals on the Daphnia magna. And Steve Williams, an expert in imaging science from the University of Manchester, UK, suggests that this information could prove useful in environmental studies. 'As an important creature in the aquatic food chain, the metabolomic status of this organism may be a barometer of the effect of pollution on the aquatic environment,' he says.

Elizabeth Davies

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