To monitor the development of the so-called annual fish, researchers raised two different species in the lab.

 

The fish could grow by almost a quarter of their body length each day. One species could already reproduce at 17 days of age. The other took an additional day. The eggs these youngsters fertilized then hatched in as little as 15 days, leaving only a month between generations. The study is in the journal EvoDevo. 

 

Embryonic annual fish survive the dry season by lying dormant underground. Once the rains return and the pool forms, they quickly reproduce before the water dries up again. Their short generation time is thus a crucial evolutionary adaptation. Their temporary ponds force them to live fast, die young and leave a desiccated corpse.