Moonlight sonata: fish's nocturnal
'singing' secrets revealed
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[September 23, 2016]
By Will Dunham
WASHINGTON (Reuters) - In one of the
marvels of nature, males of a fish species called the plainfin
midshipman that dwells in Pacific coastal waters from Alaska to Baja
California court females during breeding season using a nocturnal "love
song" with an otherworldly sound.
Scientists have wondered what makes these fish sing only at night. A
study published on Thursday provides the answer.
Laboratory experiments showed that the fish's vocalization, a
low-frequency hum like a foghorn, is controlled by a light-driven
internal clock and the hormone melatonin, known to govern sleep and wake
cycles, researchers said.
"They are among the vocal champions of the marine environment along with
whales and dolphins," said Cornell University professor of neurobiology
and behavior Andrew Bass. "The production and hearing of vocal signals
plays a central role in their social interactions and reproductive
The plainfin midshipman, up to 15 inches (38 cm) long, generally has an
olive-brown color. Its name comes from rows of bioluminescent organs on
its underside that reminded early observers of the buttons on a
Males migrate during the late spring and summer from deep offshore sites
into shallow intertidal waters, where they build nests beneath rocky
Throughout the night, they produce hums by vibrating a gas-filled
bladder within their abdomen to attract females to their nests to spawn.
One hum can last almost two hours. Neighboring males often hum together
in a chorus.
Ni Feng, who led the study in Bass' lab at Cornell and now is a Yale
University postdoctoral researcher, said the study, published in the
journal Current Biology, involved wild-caught fish kept in rooms where
lighting could be controlled.
In constant darkness, the fish hummed pretty much on schedule, thanks to
their internal clock, or circadian rhythm.
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A midshipman fish’s head is shown in this undated handout photo.
Margaret Marchaterre/Courtesy of Cornell University/Handout via
In constant brightness, a condition that lowers melatonin
production, humming was suppressed. When kept in constant light but
given a melatonin-like substitute, they continued to hum, though at
random times of the day.
Melatonin keeps day-active birds quiet at night and helps humans
fall asleep but has the reverse effect in the midshipman fish.
People have not always known what to make of the midshipman's
"In the early 1980s, a mysterious sound caused concern for houseboat
residents of Sausalito Bay, California, who suspected the source
might be the pumps of a nearby sewage plant, an underwater power
line, some secret experiment by the Navy or maybe even
extraterrestrials," Bass said.
"It turned out their houseboats were merely resonating with the
'love songs' of male midshipman fish."
(Reporting by Will Dunham; Editing by Sandra Maler)
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