The Influence of Changes in Magnetic Variations and Light–Dark Cycle on Life‐History Traits of Daphnia magna

Abstract

Day–night cycle is the main zeitgeber (time giver) for biological circadian rhythms. Recently, it was suggested that natural diurnal geomagnetic variation may also be utilized by organisms for the synchronization of these rhythms. In this study, life‐history traits in Daphnia magna were evaluated after short‐term and multigenerational exposure to 16 h day/8 h night cycle, 32 h day/16 h night cycle, diurnal geomagnetic variation of 24 h, simulated magnetic variation of 48 h, and combinations of these conditions. With short‐term exposure, the lighting mode substantially influenced the brood to brood period and the lifespan in daphnids. The brood to brood period, brood size, and body length of crustaceans similarly depended on the lighting mode during the multigenerational exposure. At the same time, an interaction of lighting mode and magnetic variations affected to a lesser extent brood to brood period, brood size, and newborn's body length. The influence of simulated diurnal variation on life‐history traits in daphnids appeared distinctly as effects of synchronization between periods of lighting mode and magnetic variations during the multigenerational exposure. Newborn's body length significantly depended on the lighting regime when the periods of both studied zeitgebers were unsynchronized, or on the interaction of light regime with magnetic variations when the periods were synchronized. These results confirm the hypothesis that diurnal geomagnetic variation is an additional zeitgeber for biological circadian rhythms. Possible mechanisms for these observed effects are discussed. Bioelectromagnetics. © 2020 Bioelectromagnetics Society

Influence of Calcium Resonance-Tuned Low-Frequency Magnetic Fields on Daphnia magna

“…Life-history traits, general amylolytic activity, general proteolytic activity, and sucrase activity were utilized to evaluate the biological effects of magnetic fields. Previously, it was shown that these characteristics are sensitive to magnetic influences [ 27 , 31 , 32 , 33 ].…”

Magnetic fluctuations affect circadian patterns of locomotor activity in zebrafish

“…Diurnal geomagnetic variation is suggested to act as a potential circadian zeitgeber via cytochromes possibly being able to perceive magnetic fields through radical pair reactions [12,13]. Though indirect evidence supports this theory [14,15,16,17,18,19,20], no direct experimentation has been carried out studying the entrainment of circadian rhythms to slow magnetic fluctuations. The issue of whether slow changes in the magnetic field affect circadian oscillators remains open.…”