Hormone Responsible For Midshipman Fish To Sing, Study Finds

By J Russ I. , Oct 19, 2016 06:33 AM EDT

There have been hundreds of studies documenting various wildlife using "songs" to achieve a particular goal. Some might use it for hunting or communication; others for mating, while there are those that just simply does.

Even animals living underwater have been observed to exhibit this behavior. And one such underwater creature is a fish known as the midshipman.

Melatonin Responsible For The Midshipman's Crooning Behavior

The fish's common name came from how its luminescent spot is patterned reminding early marine biologist of buttons lining the front of nautical uniforms. The wide-mouthed creature spends their night singing - more like a long drawn foghorn hum, really.

This nocturnal behavior among males is for mating. They dig nests under rocks along North America's Pacific Coast waiting for females drawn in by their serenade, reported Science Daily.

Recently, scientists discovered that a particular hormone that is also found in humans is responsible for prompting this remarkable vocalization. The said hormone is called melatonin, which regulates the reproductive cycle, coordinates the body's time-clock and after-dark biology.

This is the first time that the hormone has been observed to caused singing among animals, according to Andrew Bass of Cornell University. Specialized muscles around the fish's air-filled swim bladder twitched to about 100 times per second producing the steady "mmm" sound; the same muscle that shakes a rattlesnake's tail and enables the vocalization of bats and songbirds.

Midshipman Unable To Continue Singing Cycle When Exposed To Constant Light

Intrigued by this nocturnal courtship, the scientists collected several male midshipmen from shores of California and Washington state. They divided their samples into daytime and nighttime group.

Those that were placed in complete darkness followed their humming and silence routine indicating that the behavior is controlled by their body clock. However, this humming cycle was disrupted when the midshipman was exposed to constant light.

Scientists have long discovered that too much light can suppress melatonin as the hormone is primarily secreted during nighttime by the brain's pineal gland, said Popsci. When scientists infused melatonin on the daytime group, the crooning renewed despite light shining in their tank prompting the researchers to conclude that "melatonin conveys the appropriate time for vocalization."

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