In 1924, an academic called Charles Greene described how the \u201cCalifornia singing fish\u201d\u009d would hum at night. Just why the plainfin midshipman is so vocal at night remained a mystery for nearly a century, until now.<\/p>\n
For much of the year, you won\u2019t hear these fish singing at all. The plainfin midshipman, named after the bioluminescent organs on its underside, which reminded early observers of uniform buttons, resides in the depths of the ocean during the fall and winter. During the spring and early summer, they move to coastal waters between Alaska and Baja California. There, the male fish \u201csing\u201d\u009d to attract mates, a sound that can be heard by humans onshore.<\/p>\n
But these vocalizations aren\u2019t spontaneous, say Cornell University researchers Andrew Bass and Ni Feng in a new study in Current Biology. Instead, they\u2019re controlled by the fish\u2019s internal clocks. That\u2019s why they happen exclusively at night. And the hormone that controls these clocks is the same one that regulates bird activity and human sleep patterns.<\/p>\n