The Blind Cavefish | JONATHAN BIRD’S BLUE WORLD

The Blind Cavefish | JONATHAN BIRD’S BLUE WORLD


Next on Jonathan Bird’s Blue World, Jonathan goes deep underground looking for a rare and elusive blind cavefish in the Yucatan! Hi, I’m Jonathan Bird and
welcome to my world! ( ♪ music ) From the highest mountains to
the depths of the ocean, life
exists in nearly every environment on Earth. But some of these environments
are surprising. Deep beneath
the floor of this jungle lives a creature uniquely adapted for
survival in a harsh aquatic
environment. To find it, I have traveled to
the Riviera Maya in Mexico’s
Yucatan peninsula. The Yucatan is full of underwater
cave systems. My quarry is the blind
cavefish, an animal that lives
in the complete and total
darkness of caves for its entire life. To begin my quest, I head on
over to Yucatek Divers in Playa
del Carmen, where I meet
Christine Loew, who will guide my search
for this exceptionally rare
fish. We load the van in the early
morning, because we have a long
drive to a remote cenote in the jungle. Our travels take us over rough
dirt roads for miles. Finally we arrive at the
entrance to the cave, deep in
the jungle. Christine is a cave diving
instructor, someone who knows
how to keep me out of trouble in a dangerous cave. We discuss
our plan for the dive as we
walk over to check out the entrance. It might not look like much,
but this sliver of clear water
leads into a vast cave system called Pet Cemetery. I don’t
really want to know why they
call it that. Christine shows me on the map
that we will only be seeing a
tiny fraction of this massive system. Hopefully we can find
the cavefish. Christine: “And actually you
already see the line going
around. It’s forming a loop and
this “is where we head in. We will
go counter clockwise because in
that area very “likely we going to see the
cave fish.” I pay special attention to
Christine’s briefing. Diving in
caves is serious business. Next, it’s time to suit up.
Christine wears massive double tanks for cave
diving so she has extra
air—just in case. This is a cave diving protocol. We climb down a convenient set
of steps and into the warm,
clear water of the cenote, the name for an opening to an
underwater cave system that
flows deep beneath the jungle above. I grab my camera, do a few last
checks, fire up my lights, and
follow Christine into the darkness. (pause between these) Just inside the entrance, we
are already surrounded by
beautiful sculptures of rock.
I’m always astonished by the incredible
beauty of cave formations. During the last ice age, when
sea levels were much lower, the
water table was also lower. This cave was bone dry, but the
constant dripping of water from
the ceiling formed thousands of stalactites. They look like
icicles, and form nearly the
same way, except out of calcium carbonate—a kind of soft stone.
They are incredibly delicate.
If I bump them, they will break and never grow back.
Moving slowly and carefully is
my responsibility. Christine and I use a special
kind of kick called a frog
kick. Instead of kicking our fins up and down like we do in
the ocean, here we gently skull
them out to the side. This keeps from disturbing the
silty sediment on the floor of
the cave. This fine sediment is easy to
kick up and it will absolutely
destroy the visibility. If we can’t see, it’s a lot
harder to find out way out. Divers come here often and
these fish from the well-lit
cenote outside have learned to follow divers’ lights into the
darkness to hunt in the cave.
It definitely poses a threat to pristine and fragile cave
ecosystems. With our little hitchhikers in
tow, we finally reach the part
of the cave where Christine has seen the cavefish before.
Now she is carefully poking
around looking for one. Since I have never seen one,
I’m not exactly sure what to
look for! I’m surprised to see what looks
like a bush growing in the
pitch darkness of the cave. But it’s actually the roots of
a tree living in the jungle up
above. The trees up there have no problem getting plenty
of water! Christine is hunting in the
tangled maze of roots.
Sometimes the cavefish hide in
there. I can’t help but notice that
there is air above my head!
This cave actually has some very large air pockets. Since
they are connected to the
surface through tiny cracks,
the air is safe to breathe, so I stick
my head up and take a look
around. There are more
stalactites above water. Because these are
in air, they are still growing. On the bottom, Christine points
out some extremely thin and
fragile flakes of calcium. This
forms as a film on the surface of the
water below dripping
stalactites. When it gets thick
enough, it sinks to the bottom. In some
places, the flakes are stacked
up several inches thick. This little pile is hundreds of
years worth. As I continue looking for the
cavefish, I stumble across a
jawbone from some kind of animal that walked in here and
died a long time ago when it
was dry. This has to be
thousands of years old but its in
amazingly good condition. Skittering across the sand I
find a cave shrimp. This
species is not blind—but moves
between the dark and light portions of
the cave. It probably feeds on
organic material that originates with the tree roots. Life is tough in the darkness.
This is a catfish that couldn’t
find its way out. Christine searches for another
mass of tree roots that might
harbor a cavefish. When we find one, I start
looking carefully in the roots.
At last I spot it! A pinkish white fish hiding in there!
It’s great to see, but
impossible to film in that tangled mess. Fortunately for me, the fish
shies away from light and swims
out of the roots. Even though this species of fish has
evolved for thousands of years
in the complete absence of light and has no eyes, it can still
detect the presence of light
through its albino skin using a
gland in its head. Why? This fish’s
only defense is darkness. If it
wanders out of the dark part of the cave, other fish
can see it—but it won’t see
them. The blind cavefish needs to stay in the dark where it’s
safe. My lights make the cavefish
swim for cover and safety. The
fish that followed me into the cave from outside take an
interest in the cavefish. I
have to shoo them away. Although life is sparse in the
cave with very few animals able
to survive in the darkness, the cavefish does manage to
hunt down tiny crustaceans and
worms that also make this their home. In fact, in the
cave ecosystem, this little
fish is the top predator—the great white shark if you will
of the cave. With our mission complete, it’s
time for me and Christine to
turn around and head back out to the light. Christine
knows this cave like the back
of her hand, but for added
safety, we follow a line. On the line
are little plastic triangular
arrows that point the way out. We could use these in complete
darkness by feeling them and
holding on to the line the whole way. Christine stops to point out an
amazing type of stalactite. Unlike most stalactites, which
look more like icicles, these
unique formations look like elephants feet, with bulbs
instead of points on the end. They are formed when the cave
is partially filled with water
and the stalactite grows from above, eventually reaching
the water. Once the stalactite
touches the water, it flattens out. As the water
level changes, bulbs form at
different levels. Finally we are nearing the
cenote entrance and we head
back into the light. Christine explores the cenote
just under the surface, before
we head back to the steps to get out of the water. Wow, that is such a beautiful
cenote! All the formations
hanging down and everything! That was great! It’s hard to believe that there
is an entire world living under
the jungle in a submerged cave, but life survives
everywhere in the blue world,
even in complete darkness. ( ♪ music )

local_offerevent_note August 29, 2019

account_box Gilbert Heid


local_offer

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