Bristol Aquarium’s newest arrivals are a shoal of endangered tropical fish that can spend months living out of the water.

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

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.

The fish can temporarily change the structure of their gills their and metabolism to cope with life out of water.

As well as their ability to survive out of water for months at a time, the fish is also unique in that it can breed without a mate – the only known vertebrate capable of self-fertilisation.

Bristol Aquarium curator Dan de Castro said: “This particular shoal’s original habitat is the tropical mangroves in Belize.

“They are a very interesting species; not only because they are endangered in their natural environment, but also because they’re the only vertebrate capable of auto-fertilisation.

“We plan to carry out a series of studies on the fish including dietary needs, variations in colouration and also captive breeding. The great news is that several of the shoal have already laid eggs since arriving here at the aquarium,” he added.

Recently scientists discovered the mangrove killifish spends several months of the year living inside trees.

The remarkable creatures temporarily alter their biological makeup so they can breathe air, enabling them to survive out of water for long periods.

Biologists made the discovery when they found hundreds of the fish hiding in the rotting branches and trunks of trees.

They learned the fish had slithered to their new homes when the pools of water around the roots of mangrove trees dried up. Inside the logs, they were lined up end to end along tracks carved out by insects.