Oct 18 : Biologists in Florida, US have discovered that the mangrove killifish spends several months of every year out of the water to live inside trees.

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

Dr Scott Taylor of the Brevard County Environmentally Endangered Lands Programme in Florida, who discovered these fish while wading through swamps in Belize and Florida, said, he found hundreds of these creatures hiding out of the water in the branches and trunks of trees.

The fish had flopped their way to their new homes when their pools of water around the roots of mangroves dried up. Inside the logs, they lined up end to end along tracks carved out by insects, said Dr Taylor.

Around two inches long, the mangrove killifish, known by the biological name Rivulus marmoratus Poey, normally live in muddy pools and the flooded burrows of crabs in the mangrove swamps of Florida, Latin American and Caribbean.

Dr Taylor said though the fish are fiercely territorial, they curb their aggression when hiding inside logs or tree trunks, where conditions are often cramped.

Dr Taylor said the creatures are a little odd.

“They really don’t meet standard behavioural criteria for fish,” the Daily Mail quoted him as telling New Scientist magazine.

Incidentally, a previous study published earlier this year had shown that these fish alter their gills to retain water and nutrients while excreting nitrogen waste through the skin.

These changes are reversed as soon as they return to the water.

Previously, mangrove killifish’s biggest claim to fame was that they were the only known vertebrate – animal with a backbone – to reproduce without the need for a mate.

Killifish can develop both female and male sexual organs, and fertilise their eggs while they are still in the body, laying tiny embryos into the water. (ANI)

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