PMC

Diagram of the electrical disturbance of the moon to the Earth's surface (modified from: Bevington, []). (a): at new moon, the moon faces the bright side of the Earth (moon above the horizon during the daytime) and the solar wind impacts the moon. This creates an umbra and a penumbra, which are shadows of the moon body carrying negative electric charges to the Earth's surface. (b) at full moon, the moon faces the dark side of the Earth (moon above the horizon at nighttime). Following its orbit, the moon impacts the Earth's magnetotail and creates an electric disturbance of positive charges propagating towards the Earth's surface.

Moon phase influenced fecal cortisol metabolite levels in both free ranging diurnal A. russatus and nocturnal A. cahirinus. In both, fecal cortisol metabolite levels were significantly higher in full moon nights than during new moon nights. A similar pattern was found in A. russatus in the A. russatus enclosures, where they are active both during the day and during the nights.

In the two species enclosures nocturnal foraging is ascribed to A. cahirinus and diurnal foraging to A. russatus. In the A. russatus enclosures both diurnal and nocturnal foraging were carried out by A. russatus * p<0.05, ** p<0.01, ***p<0.001. A: Moon phase influenced GUDs, even during daytime: patches were foraged by A. russatus to significantly lower GUDs under new moon vs. full moon during both parts of the diel cycle. However, patches were foraged to a significantly lower GUDs during daytime than during nighttime. A. cahirinus also foraged to significantly lower GUDs under new moon. The effect of moon was significantly higher on A. cahirinus compared to A. russatus. B: Moon phase had a significant effect on patch foraging probabilities only in the two species enclosures, where during daytime A. russatus patch foraging probabilities were lower during new moon than during full moon. During nighttime A. cahirinus patch foraging probabilities were higher during new moon than full moon nights. In the A. russatus enclosures patch foraging probabilities of A. russatus were lower during nighttime compared to daytime, in which A. russatus foraged in fewer patches during nighttime regardless of moon phase. C: Moon phase influenced the amount of seeds eaten at each enclosure: A. russatus consumed a higher amount of seeds under new moon vs. full moon during both parts of the dial cycle. However, significantly less amount of seeds were eaten during A. russatus nocturnal foraging than during diurnal foraging. A. cahirinus also consumed a higher amount of seeds under new moon. Moreover, the effect of moon was not significantly different between the species.

Orientation of glass eels (Anguilla anguilla) at sea and moon-related orientation. Orientation of the glass eels, the azimuth of the moon and orientation with respect to the azimuth of the moon (as described in ), during each of the four main moon phases [(a): full moon, (b): third quarter, (c): new moon, (d): first quarter] and during each tidal phase (flood/ebb). The frame of reference of each plot is indicated: N = magnetic north, MOON = direction of the moon at the horizon (azimuth). In the first and third column, significant preferences of orientation direction are shown by a black arrow starting from the centre of the circle and pointing towards the mean orientation direction. Dashed grey lines are the 95% confidence intervals around the mean. The circular plots are empty when there was no significant preference of orientation direction. The first column i. Orientation (α_north) shows the orientation of glass eels with respect to the magnetic north (0°) and south. Each black data point represents the mean bearing of a single glass eel. Only the glass eels that had a significant individual orientation are presented. The second column, ii. Moon azimuth during the tests, shows the direction of the moon azimuth during each DISC deployment. The points are blue if the moon was below the horizon and red if the moon was above the horizon. The third column, iii. (α_moon), shows how far the glass eels were orienting from the moon azimuth (MOON, top of the plot = 0°). The angular difference between the orientation of each eel and the azimuth of the moon is shown as a navy-blue data point. Significant collective orientation towards the direction of the moon is shown as a black arrow pointing towards the top of the plot (at new moon and first quarter).