Current knowledge of lunar synchronized spawning in fish

Many organisms are sensitive to lunar cycle-related changes, such as tidal fluctuations and variations in moonlight intensity. Marine organisms must synchronize their behavior to the underwater environment, which is more complex and variable than terrestrial habitats. Lunar-synchronized spawning refers to the monthly spawning cycle triggered by changes in phase of the moon and is especially common among temperate and tropical marine species. Corals, marine worms, and fish are well-known examples of organisms that spawn synchronously with lunar phases to improve fertilization success. Research over the past decade has provided insights into lunar-synchronized spawning, and studies of families such as Siganidae and Serranidae have begun to elucidate the underlying mechanisms in fish. Field investigations, particularly in tropical and subtropical waters, have shown that many species spawn during periods of the new or full moon. Species-specific spawning times may be determined genetically, with long-term environmental adaptation influenced by physicochemical and ecological factors. Even within the same species, spawning moon phases can vary by location. As lunar-synchronized spawning is regulated by moonlight cues, these geographical differences are likely driven by genetic variation in photoresponsiveness. Physiological experiments have further suggested that nocturnal light plays a role in both gonadal development and the timing of spawning in fish. Fish have been hypothesized to be able to predict moon phases for spawning by detecting temporal changes in moonlight intensity associated with the lunar cycle.