Relationship advice from a gender-bending fish that mates for life

Date: June 9, 2016

Source: University of Florida

A 3-inch monogamous hermaphrodite proves the saying "there's plenty more fish in the sea" isn't always the case.

For the tiny fish found in the coral reefs off Panama, a lifelong relationship with its partner doesn't come without some give and take. In fact, the faithful pair owe their evolutionary success to trading male and female roles: According to an April 2016 University of Florida study in the journal of Behavioral Ecology, the fish switch genders at least 20 times each day.

This reproductive strategy allows individuals to fertilize about as many eggs as they produce, giving the neon-blue fish a reproductive edge. Its mating habits may, at first, seem complex and unusual, but UF scientist Mary Hart said the loyal chalk bass offers humans in relationships this simple wisdom: You get what you give.

"Our study indicates that animals in long-term partnerships are paying attention to whether their partner is contributing to the relationship fairly -- something many humans may identify with from their own long-term relationships," said Hart, lead author and an adjunct professor in UF's biology department.

In fact, the duo motivate one another to contribute eggs to the relationship because if one partner lacks eggs, the other will simply match whatever it produces. The only way for a partner to convince its mate to produce more eggs, is to pick up the slack and generate more itself, Hart said.

Hart worked with her husband of 10 years, co-author Andrew Kratter, an ornithologist with the Florida Museum of Natural History on the UF campus, to study the ocean-dwelling partners. For six months, the scientists observed the short-lived chalk bass, Serranus tortugarum, while scuba diving off the coast of Panama.

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