The trouble is, no one bothered to tell the mangrove killifish.

Scientists have discovered that it spends several months of every year out of the water and living inside trees

Hidden away inside rotten branches and trunks, the remarkable creatures temporarily alter their biological makeup so they can breathe air.

Biologists studying the killifish say they astonished it can cope for so long out of its natural habitat.

The discovery, along with its ability to breed without a mate, must make the mangrove killifish, Rivulus marmoratus Poey, one of the oddest fish known to man.

Around two inches long, they normally live in muddy pools and the flooded burrows of crabs in the mangrove swamps of Florida, Latin American and Caribbean.