Sex Done, Female Fish Stop Paying Attention

The head of the male midshipman fish. Credit and ©: Margaret Marchaterre.

Love may be blind, and once its over, it can be deaf, too. At least that's the case for certain female fish that appear to hear better when they are ready to reproduce. The enhancement is tied to an increase in the fish-equivalent of estrogen.

A similar correlation may be at play in humans.

The plainfin midshipman fish is known to biologists and sailors along the U.S. West Coast for the love song the male belts out when he has a nest ready for a female's eggs.

This fertility advertisement "sounds like a drone of bees or perhaps the mantra sung by those doing yoga," Andrew H. Bass from Cornell University told LiveScience.

During the late spring and summer, sailors often hear the combined chorus of the midshipman males, but research had found that females who had already laid their eggs no longer seemed to respond to the distant hum.

To determine the cause of this selective hearing, Bass and his team took female midshipman without eggs and injected them with an estrogen-like hormone that is normally elevated in egg-carrying females. They measured the electrical activity in the nerve coming from the fish's inner ear and found that the fish became sensitive to frequencies above 100 Hz only when the hormone level was increased.

This shift in spectrum-response helps the reproductive females hear the upper harmonics of the mating call, the scientists speculate, which travel further in the shallow waters where the midshipman mate.

Hormone-dependent hearing could be operating in human females. In detailing their study in the journal Science, the researchers cite other work that which has identified variations in auditory sensitivity of women corresponding to the menstrual cycle.

Furthermore, women have estrogen receptors in their ears, similar to the hormone receptors that Bass and his colleagues found in the midshipman females.

"The significance of these receptors in the human ear are unknown - our work is the first to show the possible significance of these receptors for hearing," Bass said.

If estrogen does turn up the volume, perhaps this explains why some men don't hear their wives.