Swamp Scramblers
Running across shoreline sludge,
sometimes leaping high into the air, the
mudskipper is a fish out of water. But it's
definitely not out of place.
Though they're truly fish—with fins and
gills to prove it—mudskippers are so at
home on land, they can not only walk and
breathe air, they can also climb trees.
Sound weird? Maybe, but then the world they
live in—the mangrove swamps and mud flats
of Asia, Africa, and the South Pacific—is a
pretty unusual one as well.
Covered with water at high tide and a lot of
oozing muck when the water goes back
down, these areas can seem inhospitable.
Yet mangrove trees flourish here.
Propped up by their long, stiltlike roots,
these trees are able to both rise above the
waves and stand firm in the shifting mud.
They also provide
the climbing
mudskippers with
the perfect place
to snatch a meal
of insects or
spiders and a safe
refuge at high
tide, when larger
predatory fish
patrol the water
below.
How do mudskippers move on land? The answer
lies in their fins. The sturdy fins near the front of the
fish are not only extremely strong, they're also bent
to look a lot like arms. Supporting its weight on
these fins, the mudskipper lifts its body off the
ground and pushes itself forward at the same time,
a bit like a seal.
The fins at the back of its body are the ones
the mudskipper uses when climbing. Shaped
like small suckers, they allow the fish to cling
to mangrove roots while their front fins find a
good grip even farther up the limb.
When frightened, the mudskipper can
also scurry across the mud or leap into
the air with a few powerful lashes from
its tail.
Of course, being able to move on land is no good if
you can't also breathe. Mudskippers have that
problem licked too. Amazingly, they have been
known to survive out of water for two and a half
days. Most other fish would die in just a fraction of
that time.
That's because all fish, even mudskippers, use their
gills to get oxygen from water. The gills are packed
with tiny blood vessels, and, as the water passes over
them, the oxygen in the water is absorbed into the
fish's bloodstream. Normally when fish leave the
water, their gills dry out and become useless.
Not a mudskipper's gills, though—
they're always moist!
Before leaving the water, mudskippers soak up
water into special gill chambers, which are
storage pockets located around each gill. Once on
land, the fish can absorb oxygen from this stored
water by rolling its large, movable eyes back into
its eye sockets.
This movement swirls the stored water
around the pouch and remoistens the gills.
It's a great trick, but there's one small catch:
eating.
As mudskippers
swallow insects and
other tasty treats, the
water stored in the gill
chambers floods out,
leaving the
mudskipper high and
dry. Then the fish has
to quickly scoot back
to a nearby puddle for
a refill.
But moist gills
are only part of
the answer for
the land-loving
mudskipper.
Mudskippers
can also soak up
oxygen through
their skin, as
long as it is kept
wet.
Some scientists think that's why
mudskippers roll in mud puddles or
lounge on the sun-drenched flats with
their tails in the water.