Aquarists at Bristol Aquarium are looking after a miniature shoal of cloned fish that were all born without a father.

The quintet of female mangrove killifish are identical clones of their mother and were born by a process known as parthenogenesis where the female is capable of auto-fertilisation.

Parthenogenesis is sometimes seen in insects and jellyfish, however the Mangrove killifish is the only known vertebrate capable of reproducing in this way.

Around five centimetres in length, the fish normally live in muddy pools and the flooded burrows of crabs in the mangrove swamps of Florida, Latin American and the Caribbean.

In addition to their ability to reproduce asexually it has also been discovered that the endangered tropical fish can spend months living out of the water.

The fish can temporarily change the structure of their gills and metabolism to cope with life out of water. Biologists made the discovery when they found hundreds of the fish hiding in the rotting branches and trunks of trees.

Bristol Aquarium curator Dan de Castro said: “They really are extraordinary little fish with a fascinating life cycle.

“In theory a single female can create a whole new population of genetically identical individuals.

“Although all females are capable of auto-fertilisation there are also plenty of male fish in the wild. Their main role is creating a more genetically diverse population of this species.

“This fish lives in an environment where there are lots of incidents of drought and the capacity to be able to survive out of water and for isolated females to still be able to reproduce help ensure the long-term survival of the species,” he added.

The bizarre mangrove killifish are part of a joint captive breeding programme with Aberystwyth University.