The fish that can survive for months in a tree
It's one of the golden rules of the natural world – birds live in trees,
fish live in water.
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.
"They really don't meet standard behavioural criteria for fish," he told
New Scientist magazine. Although the cracks inside logs make a perfect
hiding place, conditions can be cramped. The fish – which are usually fiercely
territorial – are forced to curb their aggression. Another study,
published earlier this year, revealed how they alter their bodies and metabolism
to cope with life out of water.
Their gills are altered to retain water and nutrients, while they
excrete nitrogen waste through their skin. These changes are
reversed as soon as they return to the water.
Previously their biggest claim to fame was that they are 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.
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