At the time of the spring tide (new moon and full moon), thousands of puffer fish around the world head for the coastlines to spawn. There, they gather at the water’s edge and vigorously tremble their bodies to spawn.

Scientists have long wondered how the puffer fish were able to synchronise their spawning with the lunar cycle.

A paper published in a recent issue of the Current Biology journal has the answers. 

In the lab, the researchers at the Institute of Transformative Bio-Molecules at Nagoya University identified 125 genes involved in the fish's spawning behaviour. At the same time, they also noticed receptors for PGE₂, a pheromone. 

They discovered that after applying PGE₂ to a tank containing male and female puffer fish, the fish displayed the typical writhing behaviour their species would exhibit whenever they spawn.

In addition, whenever the dosage of PGE₂ was increased, so did the number of fish that responded. 

According to lead researcher Professor Takashi Yoshimura, "the synchronisation of reproduction with the lunar cycle is not limited to organisms living along the shoreline.” He proceeded to cite examples of wildebeest mating and calf delivery in cows, as well as menstrual cycles, sleep–wake cycles, and manic–depressive cycles in humans, that were synchronised to the lunar cycle.