This crazy monogamous fish changes sex 20 times per day. Why?

JULY 7, 2016

by Chuck Bednar

Monogamy and hermaphroditism are not all that uncommon in the animal kingdom, but put both of these traits together and ramp them up to 11 and you have an unusual type of fish that changes its sex role more than 20 times per day while remaining faithful to its life partner.

This unusual species is known as the chalk bass (Serranus tortugarum), and according to a new study published recently in the journal Behavioral Ecology, this tiny reef fish lives in Panama, is neon green in color, grows to more than three inches in length, and enters a lifelong relationship with a mate that requires it to rapidly switch between male and female roles.

According to National Geographic, chalk bass utilize a reproductive technique known as “egg trading” in which they split their daily egg clutch into small groups, then alternate sex roles in repeated spawning bouts to ensure that they can fertilize as many eggs as they make. Switching roles encourages reciprocation and faithfulness from their mates, the study said.

“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,” lead author Mary Hart, an adjunct biology professor at the University of Florida, said in a statement.

Unexpected behavior appears to provide a reproductive advantage

Switching sex roles is key to the survival of the chalk bass, Hart explained, because it is the only way that a member of the species can make sure its partner is contributing equally. Basically, if a member of the species wants its mate to produce more eggs, it first has to lead by example.

Hart told Nat Geo that, during her observations of the species, she found that individuals would rarely produce more than two egg parcels at one time before changing sex roles and encouraging their mate to follow their example. Her team monitored the chalk bass for six months and found that all of the couples remained together the entire time that both were living at the site.

Read more at 

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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