Moonlight cycles synchronize oyster behaviour

Abstract

Organisms possess endogenous clock mechanisms that are synchronized to external cues and orchestrate biological rhythms. Internal timing confers the advantage of being able to anticipate environmental cycles inherent in life on Earth and to prepare accordingly. Moonlight-entrained rhythms are poorly described, being much less investigated than circadian and circannual rhythms synchronized by sunlight. Yet focus on these lunar rhythms is highly relevant to understanding temporal organization of biological processes. Here, we investigate moonlight cycle effects on valve activity behaviour of the oyster Crassostrea gigas. Our results show that oysters modulate valve behaviour according to both intensity and direction of the lunar illumination cycle. As a consequence, valve opening amplitude is significantly increased at third quarter Moons (decreasing lunar illumination) compared with first quarter Moons (increasing lunar illumination) despite identical lunar illumination, and this indicates that oyster modulation of valve behaviour by moonlight cycles is not a direct response to lunar illumination. We propose that oysters use moonlight cycles to synchronize behaviour and also other physiological and ecological aspects of this benthic mollusc bivalve.

Evidence of separate influence of moon and sun on light synchronization of mussel’s daily rhythm during the polar night

“…gigas showed a maximal VOA during the new moon, the darkest time of the night. 25 , 29 In contrast, we show here that during PN the mussels increase their VOA during the full moon, when moon light intensity is maximal. At an annual scale, we observed a higher VOA when the photoperiod and light intensity increased, 30 suggesting a photophilic behavioral pattern.…”

Rhythms during the polar night: evidence of clock-gene oscillations in the Arctic scallopChlamys islandica

“…UV radiation provides robust daily cycles at polar latitudes and could be used as zeitgeber by Arctic organisms [49,50]. Very low light intensity perception could also not be limited to polar environments since previous studies demonstrated the perception of moonlight by marine organisms [18,51,52]. Nevertheless, Arctic scallops appeared highly sensitive to light since the reported mean irradiance during the PN in Svalbard ranges from 1 to 1.5 × 10 −5 µmol photons m −2 s −1 (with a maximum position of the sun at −9°).…”

The impacts of artificial light at night on the ecology of temperate and tropical reefs

“…Similarly, predation and foraging rates of many reef organisms increase or decrease with intensity of nocturnal illumination. For example, herbivores, such as sea urchins (Echinometra viridis and Echinometra lucunter, [61]) and oysters (Crassostrea gigas, [62]) have been shown to increase foraging and filtration activity at night during the new moon, under the cover of darkness, whereas evidence of increased catch rates and activity patterns suggests piscivorous fishes increase feeding activity with both the full and new moon [63][64][65]. The ability to perceive minute changes in dim nocturnal light suggests that these organisms are susceptible to impacts from ALAN.…”