| GUATEMALA CITY
GUATEMALA CITY A tropical fish that lives in
mangrove swamps across the Americas can survive out of water
for months at a time, similar to how animals adapted to land
millions of years ago, a new study shows.
The Mangrove Rivulus, a type of small tropical killifish,
seeks refuge in shallow pools of water in crab burrows, coconut
shells or even old beer cans in the tropical mangrove swamps of
Belize, the United States and Brazil.
When their habitat dries up, they live on the land in logs,
said Scott Taylor, a researcher at the Brevard County
Environmentally Endangered Lands Program in central Florida.
The fish, whose scientific name is Rivulus marmoratus, can
grow as large as three inches (7.6 cm). They group together in
logs hollowed out by insects and breathe air through their skin
instead of their gills until they can find water again.
The scientific breakthrough came after a trip to Belize.
"We kicked over a log and the fish just came tumbling out,"
Taylor told Reuters in neighbouring Guatemala by telephone. He
said he will publish his study on the fish in The American
Naturalist journal early next year.
In lab tests, Taylor said he found the fish can survive for
up to 66 days out of water without eating, and their metabolism
CLUE TO EVOLUTION
Some other fish can survive briefly out of water. The
walking catfish found in Southeast Asia can wriggle over land
for hours at a time, while lungfish found in Australia, Africa
and South America can survive out of water, but only in a
No other known fish can be out of water as long as the
Mangrove Rivulus and remain active, according to Patricia
Wright, a biologist at Canada's University of Guelph.
"They can survive for weeks without really dropping their
metabolic rate. They remain relatively responsive and active
for weeks in air," she said.
The fish may hold clues to how animals evolved over time.
"These animals live in an environment that is similar to
conditions that existed millions of year ago, when animals
began making the transition from water onto land," she added.
Surviving on land is not the only unusual behaviour
exhibited by the fish. They have both testes and ovaries and
essentially clone themselves by laying their own, already
"This is probably the coolest fish around, not only do they
have a very bizarre sex life, but they really don't meet
standard behavioural criteria for fishes," said Taylor in a
summary of his paper.
(Editing by Sandra Maler)