Fish goes from egg to maturity in just 14 days

The turquoise killifish (Nothobranchius furzeri) from Africa can reach sexual maturity in just 14 days, making it the fastest maturing vertebrate on record.

The species has a stop-start life history strategy suited to life in the ephemeral pools and puddles of the savannahs of Africa. Tiny embryos in a state of inactivity known as diapause survive in dry sediments, and spring to life when rain falls. A short life cycle of rapid maturation and breeding ensues before the puddles dry.

The small and colourful fishes have long been study models for the ageing process, and a full genome has been sequenced, but until now the remarkably short 10 day maturation period had not been recorded.

“We guessed that some populations of this species could achieve very rapid growth and sexual maturation under particular conditions,” says Martin Reichard from the Czech Academy of Sciences, who led the latest research.

“But we have found that this rapid maturation is the norm rather than a rare exception.”

The killifish life-cycle has been studied extensively in laboratory conditions, and the maturation period has ranged from 18 days to as long as 10 weeks. Reichard and his team decided to observe the fish in its natural habitat, southern Mozambique.

The team collected fish from eight separate pools between January and May 2016, within three weeks of the pools first finning with rainwater. They used a combination of otolith (ear bone) ageing and careful examination of gonads of both sexes.

The findings, published in the journal Current Biology, reveal that Nothobranchius furzeri is capable of reaching sexual maturity just 14 days after hatching, the fastest rate of sexual maturation recorded for any vertebrate.

In the lab, killifish which reach sexual maturity in a short time span such as 18 days deteriorate rapidly after breeding and only live for only four to six months. The species pays the price of rapid maturity with a shorter lifespan. In the wild, the strategy means that even a pool that dried out after three weeks was able to support one entire life cycle.

This type of life history strategy, with an embryo sealed in a protective case, is more commonly seen in invertebrates such as sand shrimp and other small animals.

“The killifish combines a vertebrate body plan with a characteristically invertebrate solution to survival in unpredictable conditions,” adds Reichard.

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