The mysteries of the singing fish at San Francisco Bay have been recently revealed. Researchers discovered that the singing fish try to attract mates through their songs. However, they found how melatonin and daily light cycles support the fish in keeping a tab on the coordination of their humming from late evening to the morning.
Until now, scientists did not have much information on how Melatonin and the circadian rhythms work for fish and other nocturnal vertebrates that hum during the mating period. Other research regarding diurnal songbirds proved that melatonin enhances the duration of syllables when birds sing and suppresses singing at night.
However, the effect of melatonin on the singing fish is opposite to the effect on diurnal birds. The release of this hormone provides a signal for the fish to sing and similar to the diurnal birds, it also acts to lengthen notes when the fish hum.
Andrew Bass, the lead author of the study and a professor at the New York Cornell University, highlights that the hormones usually control the output of neural networks in the brain to manage distinct elements of behavior.
Relying on the timescale of response, from the duration of single calls to the day-night rhythms, one hormone can exert different or similar consequences in nocturnal vs. diurnal species.
For the study, researchers brought the midshipman fish also known as Porichthys notatus into a lab where they could modify the lighting for a better analysis of the fish’s reactions.
When the fish encountered constant darkness for seven days at a time, it still sang but on a 25-hour schedule so they began with one hour delay each night.
The researchers also examined what occurred to the melatonin’s effects on behavior when they exposed the fish to a ten-day constant exposure to daylight.
The findings proved that constant exposure to light suppresses the fish’s humming proving that the pineal gland provides melatonin in vertebrates but only in the nighttime. However, when the fish were given a melatonin replacement, they continued to sing, though without a rhythm and only at several random times a day.
Researchers also noted that the brain region also is equipped with melatonin receptors that control the social and reproductive behaviors including vocal initiation cores, similar to those found in birds and other vertebrates.
Image source: Wikipedia