Breeding activities at full moon
On a full moon night in November, more than 130 species of corals on Australia’s Great Barrier Reef begin to ovulate simultaneously. Some corals, like volcanic eruptions, squirt sperm out of the coral, while others emit large amounts of eggs. But most of the corals are hermaphroditic, which emits a bundle of spermatophores (containing eggs and sperm) that glow with pink, orange, and yellow light, and after a short stay with their parents, like colorful Like a balloon, it drifts into the distance.
This is a wonderful moment. The sea is full of colorful sperm bunches. In some places, there is a mist of sperm. Fish, sea otters and predatory invertebrates swim fast in the water and eat. Colorful coral clusters of eggs, the entire ocean seems to be holding a carnival. In the moonlight, coral eggs and sperm from different regions begin to fuse, giving birth to larvae that eventually settle on the seabed and form new corals.
Corals choose a model of collective reproduction that can increase the chances of egg fertilization, while the huge tides that provoke the full moon impact the coral reefs, which will greatly increase the chances of coral larvae spreading. But how does coral achieve synchronous reproduction? In addition to the water temperature and the length of the chalk affecting them, another important factor is the moonlight.
The researchers found that there is a blue-light-inducing protein in the coral that senses the blue wavelength of the moonlight and initiates the breeding season. And they also have genes that regulate their activities to match the tide cycle. If the night sky is cloudy and the moon is blocked, the corals usually do not lay eggs, and sometimes they will postpone until the next full moon to lay eggs.
a large-scale breeding activity
Not only does the coral’s breeding period coincide with the moon’s activity, but the tides caused by the moon usually mark the beginning of large-scale breeding activities.
At some stages of the moon phase, Japanese crabs rushed down the slopes of the mountains and rushed to the river to discharge eggs and sperm. At the end of October each year, when the rain in the rainforest comes, on the Christmas Island in the Indian Ocean in the northwest of Australia, the red crabs make up millions of crabs, leaving their comfortable caves in the jungle, climbing to the beach to mate and lay eggs. The migration is also related to the intensity of the moonlight activity. The researchers found that Christmas Island Red Crabs rushed to the beach to ovulate when the waning moon appeared. This is because the tide caused by the residual moon is smaller, and the fluctuation of the sea surface is not large, so that the descendants of the Christmas Island Red Crab can survive better. The moonlight even makes the horseshoe crab’s vision more acute, and they climb to shore to mate on certain nights. Similarly, studies have shown that moonlight is one of the environmental incentives for the simultaneous spawning of tropical rabbit fish, which may promote the secretion of gonadotropins in these fish, thereby promoting the maturity of gametes.
In 2013, neurobiologists at the University of Marburg in Germany found some of the most convincing evidence that there is also a moon circadian clock at the molecular level in marine organisms. They studied the swine worms, which live on the seaweeds and rocks on the seabed and look like an amber scorpion with many feet on either side of the body.
In the 1950s and 1960s, researchers discovered that some wild swine worm populations would mature sexually after the new moon, then swim to the surface of the ocean and use dance to courtship. This mating ritual will be synchronized with the moonlight. But how do they do it?
To learn more, the researchers studied pig worms, which used lights to simulate normal and abnormal moon cycles. The results showed that the swine worms that grew up in the circadian cycle without the moon never showed a reproductive rhythm. However, swine worms that grow up in nighttime illumination will synchronize their spawning rituals with the artificial moon.
Researchers have discovered light-sensitive neurons in the forebrain of swine worms. Gene sequencing shows that, like terrestrial insects and vertebrates, this swine worm has its important molecular clock gene. The products of these clock genes can regulate their own expression, so that some physiological functions and biochemical activities of swine worms follow the moon. Changes in the cycle.
Therefore, just as sunlight regulates the circadian rhythm of living things, there are also biological molecules that sense the moonlight in the living body, regulating their own body activities.
More effects of moonlight
Moonlight not only regulates the reproduction of some marine life, it also plays an important role in other aspects. At the full moon, the trout in the migration will swim in the shallower ocean areas, and they will swim faster; albatrosses and seagulls will fly more often and fly longer, perhaps because the full moon makes them look Be more clear, be able to travel further, or to avoid those marine predators. On the day before the new moon, the newborn rabbit fish will migrate to the coral reefs in groups through the cover of the night.
Even plankton is affected by the moonlight. In the oceans around the world, plankton will move deeper into the ocean during the day, resurface in the night, and feed in shallow water under the cover of night. Scientists are not sure what drives this circadian rhythm, but guess their biological clock should be in sync with the sun. However, when the Arctic winter arrived, in some Arctic ocean areas where the sun never shined, recent research has shown that the biological clock of the creature is synchronized with the moonlight.
Some animals are still using moonlight camouflage. During the day, the squid, the squid, hides in the sand at the bottom of the sea to avoid predators. In the evening, they will come out to eat and feed on shrimp and insects. As they left the sea floor and were exposed to potential dangers, these tiny mollusks chose a trick – using moonlight camouflage.
In the coat of the short-tailed squid, some of the luminescent bacteria emit light similar to moonlight and starlight, so that the short-tailed squid can achieve stealth. Several other species, including deep-sea fish, crustaceans and squid, are using similar strategies.
Therefore, we humans think that the insignificant moonlight actually plays an important role in the ocean like daylight.