How Fish Hear A Summer Mating Call
Plainfin midshipman fish live in the Pacific Ocean off the West Coast, from Alaska to Baja, California. Each summer they leave their deep water habitat and head for intertidal zones to mate. There the male fish nests and attracts females with a nighttime mating call that sounds like a deep hum.
Now scientists have figured out that the females’ ability to detect the mating call increases in summer because of a seasonal reduction in dopamine. The research by Ph.D. student Jonathan Perelmuter and Professor Paul Forlano (Brooklyn College, The Graduate Center) appeared in Current Biology.
Dopamine has an inhibitory effect on the sensory hair cells in the fish’s inner ear, making their hearing less sensitive. But in the summer, when the fish mate, “there is actually a reduction of dopamine and less of its inhibitory receptor in the inner ear of females,” Forlano said. That means the females’ hearing sensitivity increases at just the right time to “detect a male’s mating call and reproduce.”
Earlier research by Forlano had identified the dopamine pathway from the fish’s brain to the inner ear, marking the first time this had been seen in a non-mammalian vertebrate. But the reason for the pathway was unclear until this latest study.
Dopamine is a naturally occurring hormone and neurotransmitter that sends signals to other cells. In humans, dopamine increases are triggered by many addictive drugs and by certain types of behavior involving rewards, attention, and motivation. Dopamine also helps regulate motor control. Parkinson’s disease destroys the nerve cells that make dopamine.
In their conclusion, the researchers suggest that “dopamine may similarly mediate peripheral auditory plasticity in other seasonally breeding vocal species,” like frogs and birds, and may “play an important role in the peripheral encoding of social-acoustic signals across vertebrates.”