Eich, Charlotte (2017) The influence of an external magnetic field on the spinose planktonic foraminifer Globigerinoides ruber. (Master thesis), Christian-Albrechts-Universität Kiel, Kiel, Germany, 50 pp.

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Abstract

The planktonic foraminifer Globigerinoides ruber shows a semilunar gametogenesis cycle. It has been proposed that the changes of the Earth's magnetic field during full and new moon (in the order of ~10 - 100 nT) are the trigger for their simultaneous gamete release, yet no experiments have been conducted to test this hypothesis. In my MSc research project I carried out an experiment using an external magnetic field of roughly the same strength as the Earth's magnetic field (~69 μT, Earth's magnetic field: ~50 μT) to see whether this magnetic field acts as a trigger for simultaneous gametogenesis in G. ruber. All experiments were performed aboard the research vessle Maria S. Merian (MSM58, 09/09 - 07/10/2016, from Reykjavik (Iceland) to Ponta Delgada (Azores, Portugal)) under constant light and temperature conditions. Foraminifera in the treatment group were exposed to the additional magnetic field, while control specimens were kept without an additional external magnetic field. A shift to earlier gametogenesis was detected for foraminifera under treatment. I thus propose that simultaneous foraminiferal gametogenesis can be triggered by an external magnetic field, supporting the theory that the Earth's magnetic field changes over the lunar cycle act as a trigger for synchronizing gametogenesis. It has to be tested whether magnetic field changes in the order of the changes over the lunar cycle (~10 to 100 nT) can act as a trigger, too, and what the mechanisms behind detecting magnetic field changes is. Moreover, differences between foraminifera caught north, south and within the Azores Current were found. Fewer foraminifera from the southern stations underwent gametogenesis than from the other groups. It needs to be tested whether these differences could be caused by differences within the haplotype or by phenotypic plasticity and whether foraminifera north, south and within the Azores Current are different populations, subspecies or even cryptic species. The suggested reactions on the gametogenesis of G. ruber due to changes of the Earth's magnetic field could also account for simultaneous gametogenesis events in other foraminiferal species and planktonic organisms.

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