In 1924, an academic called Charles Greene described how the “California singing fish” would hum at night. Just why the plainfin midshipman is so vocal at night remained a mystery for nearly a century, until now.
For much of the year, you won’t 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 “sing” to attract mates, a sound that can be heard by humans onshore.
But these vocalizations aren’t spontaneous, say Cornell University researchers Andrew Bass and Ni Feng in a new study in Current Biology. Instead, they’re controlled by the fish’s internal clocks. That’s 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.