One species of killifish -- Nothobranchius kadleci -- started to reproduce just 17 days after hatching, researchers at the Institute of Vertebrate Biology in the Academy of Sciences of the Czech Republic said.
The scientists say they also found some eggs reached hatching stage in 15 days, the shortest minimum generation time of any vertebrate.
Martin Reichard and institute colleagues studied the aging processes of two species of wild-caught fishes from southern Mozambique that live in extreme conditions of temporary pools that only occur during the rainy season when savannah depressions are filled with water.
"It is biologically very relevant for these fish to be able to sexually mature very fast because their habitat may dry out in three to four weeks," Reichard told the BBC. "If they mature very fast, they can produce a new generation."
The fish also demonstrated rapid growth rates, the researchers said, with some growing nearly a quarter of their total body length per day.
Rapid growth, early sexual maturation and quick reproductive cycles are common traits typical of extremophiles, organisms inhabiting temporary and unpredictable habitats, the researchers said.
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