How moon influences the behavior of living creatures is a complex and debatable issue. Although more research is still required to clearly see the impact of moon on human, scientists do find that moon can modulate many fundamental behaviors in animals, including spawning.
For instance, on the Great Barrier Reef, different corals often spawn at the same time in the late spring and early summer, immediately after the full moon.
It is unknown how the spawning in different corals can be harmonized and whether moonlight affects this behavior.
To answer the questions, researchers conducted field and outdoor aquaria observations. Their finding is recently published in eLife.
They found that corals can experience moonlight, which is very important to synchronize the spawning. Although corals are simple animals that do not have eyes, they do contain molecules sensitive to light.
The gamete release in corals (i.e. release of eggs and sperm cells) is triggered by a protein similar to a photosensitive molecule called melanopsin.
In mammals, melanopsin plays a critical role in synchronizing circadian rhythms with the daily light-dark cycle.
It can also boost the activation of G-proteins, which help transit from outside a cell to the appropriate destination inside it – in response to changes in light conditions.
Researchers found that in moonlight, the activation of G-proteins is up-regulated and cascaded in corals. This might explain the moonlight sensing.
The release of gametes is also influenced by neuropeptides. During coral spawning, neuropeptide receptors that couple the G-proteins change their expressions.
When such receptors are activated, inside the cell the amount of calcium increases. Ion channels belonging to the receptors are also upregulated during spawning, which provide another route for calcium ions to enter cells.
The properties of the moonlight can also affect the coral spawning behavior. Specific parts of the light spectrum, particularly blue and green light, are critical for gamete release. However, the molecular basis of this selectivity needs future research.
Taken together, this research lays a firm foundation for future studies about coral spawning.
It will be interesting to know how different corals respond to moonlight, how coral reproduce during different lunar phases, and what happens when spawning is less synchronized.
Citation: Zoccola D, Tambutte S. (2015) Sex under the moon. eLife, 4:e12936. doi: http://dx.doi.org/10.7554/eLife.12936
Kaniewska P, Alon S, Karako-Lampert S, Hoegh-Guldberg O, Levy O. (2015). Signaling cascades and the importance of moonlight in coral broadcast mass spawning. eLife, 4:e09991. doi: http://dx.doi.org/10.7554/eLife.09991
Figure legend: This Knowridge.com image is derived from “Zoccola D, Tambutte S. (2015) Sex under the moon. eLife, 4:e12936. doi: http://dx.doi.org/10.7554/eLife.12936” under CC-BY license.