Lunar Rhythms in Mussel Behavior

To determine the existence of individual mussel’s lunar month rhythm based on the synodic lunar cycles lasting 29.53 days, chronobiological analysis were applied on the 2017–2018 PN-period, comprising 4 entire synodic lunar cycles. Such chronobiological analysis couldn’t be done in the first PN studied (2016–2017) at the monthly scale due to the absence of data during 15 days during this time due to electrical failures. Lunar month periodicity of behavioral rhythm was defined significant for a period of 29.53days ±5 days. To calculate VOA according to the moon phases (full moon, first quarter of the moon, new moon and third quarter of the moon), we measured for each mussel the mean of VOA during 3 days around the exact date of each moon phase, and so for each of the 4 lunar-month cycles comprised in PN.
Then, we determined daily rhythms. In this study, we used the term daily for all periods found in the range 18-30h, entrained by a 24h sun daily cycle (solar day) or a 24.8h lunar daily cycle (lunidian day). The extent of the classic circadian range (20-28h) previously defined for terrestrial animals was set to consider possible looser periodicity in unsynchronized conditions or weakly synchronized for aquatic organisms in PN.
To determine rhythm at the daily scale, the two PN were analyzed. These two PN were divided in several intervals according to the lunar day cycles (see details Tables S1 and S2).